Psyche: A Journal of Entomology Psyche: A Journal of Entomology Volume 2011 ISSN: 0033-2615 (Print), ISSN: 1687-7438 (Online), DOI: 10.1155/6152 Copyright © 2011 Hindawi Publishing Corporation. All rights reserved. This is volume 2011 of “Psyche: A Journal of Entomology.” All articles are open access articles distributed under the Creative Commons At- tribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Contents Immune Response of Mormon Crickets That Survived Infection by Beauveria bassiana Robert B. Srygley and Stefan T. Jaronski Volume 2011, Article ID 849038, 5 pages Diel Behavioral Activity Patterns in Adult Solitarious Desert Locust, Schistocerca gregaria (Forskal) Sidi Ould Ely, Peter G. N. Njagi, Magzoub Omer Bashir, Salah El-Tom El-Amin, and Ahmed Hassanali Volume 2011, Article ID 459315, 9 pages Application of General Circulation Models to Assess the Potential Impact of Climate Change on Potential Distribution and Relative Abundance of Melanoplus sanguinipes (Fabricius) (Orthoptera: Acrididae) in North America O. Olfert, R. M. Weiss, and D. Kriticos Volume 2011, Article ID 980372, 9 pages Phase-Dependent Color Polyphenism in Field Populations of Red Locust Nymphs ( Nomadacris septemfasciata Serv.) in Madagascar Michel Lecoq, Abdou Chamouine, and My-Hanh Luong-Skovmand Volume 2011, Article ID 105352, 12 pages Density-Dependent Phase Polyphenism in Nonmodel Locusts: A Minireview Hojun Song Volume 2011, Article ID 741769, 16 pages Distribution Patterns of Grasshoppers and Their Kin in the Boreal Zone Michael G. Sergeev Volume 2011, Article ID 324130, 9 pages Relationships between Plant Diversity and Grasshopper Diversity and Abundance in the Little Missouri National Grassland David H. Branson Volume 2011, Article ID 748635, 7 pages The Ontology of Biological Groups: Do Grasshoppers Form Assemblages, Communities, Guilds, Populations, or Something Else? Jeffrey A. Lockwood Volume 2011, Article ID 501983, 9 pages Mites (Acari) Associated with the Desert Seed Harvester Ant, Messor pergandei (Mayr) Kaitlin A. Uppstrom and Hans Klompen Volume 2011, Article ID 974646, 7 pages Locusts and Grasshoppers: Behavior, Ecology, and Biogeography Alexandre Latchininsky, Gregory Sword, Michael Sergeev, Maria Marta Cigliano, and Michel Lecoq Volume 2011, Article ID 578327, 4 pages Observations on Forced Colony Emigration in Parachartergus fraternus (Hymenoptera: Vespidae: Epiponini): New Nest Site Marked with Sprayed Venom Sidnei Mateus Volume 2011, Article ID 157149, 8 pages Diversity of Social Wasps on Semideciduous Seasonal Forest Fragments with Different Surrounding Matrix in Brazil Getulio Minoru Tanaka Junior and Fernando Barbosa Noll Volume 2011, Article ID 861747, 8 pages Production Efficiency of Cocoon Shell of Silkworm, Bombyx mori L. (Bombycidae: Lepidoptera), as an Index for Evaluating the Nutritive Value of Mulberry, Morus sp. 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Srygley and S. T. Jaronski. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Beauveria bassiana (Fungi: Ascomycota) is an entomopathogenic fungus that serves as a biological control agent of Mormon crickets Anabrus simplex Haldeman (Orthoptera: Tettigoniidae) and other grasshopper pests. To measure the dose-dependent response of Mormon crickets to fungal attack, we applied B. bassiana strain GHA topically to adults using doses of 5.13 X 10 4 to 1.75 X 10 6 conidia in sunflower oil, with oil only as a control. After three weeks, we assessed the survivors’ hemolymph for fungal cells, active phenoloxidase (PO), and lysozyme. Mortality increased and body mass of survivors decreased with conidial dose, survivors’ PO activity was elevated to the same level independent of dose. Those with fungal cells visible in their hemolymph did not differ in PO activity from those with clear hemolymph. We conclude that circulating PO may be an important enzymatic defense against Beauveria infection and that it is associated with attempted clearing of Beauveria blastospores and hyphae from Mormon cricket hemolymph. 1. Introduction Nomadic insects risk contact with fungal pathogens [1]. Mormon crickets, a long-horned grasshopper or katydid, form bands and march across western United States grass- lands seeking food, salt, and oviposition sites (Figure 1, [2, 3]). Wingless, they must walk, which increases the risk of contacting insect-pathogenic ascomycetous fungi, such as Beauveria spp. and Metarhizium spp., on plants or soil [4]. These fungal pathogens occur naturally, but some strains, such as the commercial Beauveria bassiana GHA, may be applied artificially as control agents. The ability of the fungus to infect an insect depends on its ability to adhere and penetrate the exoskeleton, resist the insect’s hemolymph-borne defenses, and grow rapidly [5]. The conidium adheres to the cuticle and germinates to penetrate the exoskeleton with a combination of mechanical pressure and a cocktail of lytic enzymes. The insect may respond to the wounding with local induction of the phenoloxidase (PO) cascade, resulting in production of toxic quinones and cuticular melanization. Following penetration into the hemolymph, the fungus grows as a yeast-like blastospore or as short lengths of vegetative hyphae. Insect defenses include encapsulation of the fungus by granulocytes and plasmatocytes (both circulating hemocytes) and forma- tion of a nodule that may be melanized [6]. Grasshoppers may also respond with behavioral fevers, elevating body temperature to inhibit fungal growth [7, 8] . Mormon crickets do not demonstrate behavioral fever per se; their preferred body temperatures are 34-37° C [9] , above the upper thermal limit for most entomopathogenic Ascomycetes. Death of the host may result from competition with the pathogen for nutrients, mechanical damage resulting from hyphal growth, and fungal toxins [5]. The humoral defenses of insects to pathogenic fungi have only been investigated in a handful of species. Metarhizium infection may result in declining hemolymph protein and PO titres over the course of the infection until death ( Schistocerca gregaria [10], Locusta migratoria [6]) whereas Beauveria infection increases active PO levels ( Melanoplus sanguinipes [11], Spodoptera exigua [12]). Lysozyme activity may decline ( Schistocerca gregaria [10]) or remain unchanged 2 Psyche ( Spodoptera exigua [13]). In this paper, we investigate circu- lating PO and lysozyme titres in adult Mormon crickets that have successfully defended themselves against invasion from topically applied Beauveria bassiana strain GHA. On range- land and crops, control agents are frequently not applied until Mormon crickets have reached the adult stage because the public demand for control is greatest when Mormon crickets have banded together and migrated from natal sites into habitats where they interfere with human activities. 2. Materials and Methods 2.1. Fungal Conidia. The B. bassiana conidia were obtained from Laverlam International (Butte, Montana, USA.) as a dry technical grade conidial powder. Conidial viability was determined by plating aqueous conidial suspensions onto quarter-strength potato dextrose agar, incubating the fungi at 28°C for 18-20 hr, then examining with 400x phase-contrast microscopy for germination. A conidium was considered germinated and thus viable if a germination peg was visible. A concentrated stock suspension in sunflower oil was prepared from the dry conidia, and the concentration was determined by hemocytometer counts of kerosene- diluted samples and adjusted for conidial viability. Working dilutions were prepared from the two concentrates using positive displacement pipettes, and the exact concentrations were determined by hemocytometer counts of kerosene - diluted samples. All conidia concentrations are viable conidia per unit volume. 2.2. B. Bassiana Dose Response. Adult Mormon crickets were collected at Lodge Grass, Montana on July 17, 2007, and fungal treatments were topically applied on July 24 (1st replicate) and July 25 (2nd replicate) to the base of the first leg, including the following fungal doses suspended in 1 p\ sunflower oil: 1.75 * 10 6 , 1.07 * 10 6 , 3.54 * 10 5 , 1.13 * 10 5 , or 5.13 * 10 4 conidia/fd B. bassiana strain GHA or a control treatment of only sunflower oil. Survivorship was measured over 21 days at 28° C. 2.3. Immunity Assays and Total Protein. After three weeks, we drew hemolymph from the surviving adults (five males and five females for each treatment, fewer if there were not enough survivors) to assess spontaneously active PO, lysozyme-like activity, and total hemolymph protein. We measured the body mass of each cricket to the nearest mg with an Ohaus microbalance (model AV53) and then punctured the arthrodial membrane at the base of the hind leg of each insect with a 26 gauge hypodermic needle so that it exuded hemolymph. A total of 14 pL of hemolymph was collected into a capillary tube, with a second puncture performed when necessary. For assays of PO activity and total hemolymph protein, the hemolymph was diluted 1 : 50 with phosphate buffered saline (PBS) solution and frozen at -20°C. An additional ID pL hemolymph diluted 1:10 with PBS was stored at -20° C for subsequent measuring of lysozyme activity. For ten insects, we did not collect sufficient blood for all of the tests. Figure 1: Migrating Mormon crickets basking near Jarbidge, Nevada in July 2009. To measure PO activity, we followed the protocol of Wilson et al. [8]. Samples of thawed hemolymph diluted in PBS were centrifuged (4°C, 10,300 rpm for 10 minutes) and activated with 10 mM dopamine solution. The plate was loaded into a temperature-controlled BioTek microplate reader (25°C), and absorbance at 492 nm was read between 5 and 15 minutes. If sample absorbance was linearly related with time, we calculated mean V (change in absorbance min- 1 ). One unit PO activity per ml hemolymph is defined as the amount of enzyme resulting in a 0.001 increase in absorbance. To measure lysozyme-like antibacterial activity, a tur- bidimetric method was used, following the protocol of de Azambuja et al. [14]. Thawed and PBS-diluted hemolymph was added to a well with suspended gram-positive bacteria cells Micrococcus lysodeikticus (Worthington). Clearing of the well was compared to a serial dilution of egg-white lysozyme (Sigma) added to the bacteria suspension. The plate was loaded into a temperature-controlled Biotek microplate reader (25°C), and absorbance at 450 nm was read between 10 and 30 minutes. If the sample absorbance was linearly related with time, we would calculate mean V. When sample activity fell below 6.5 pg ml' 1 , the sample was excluded because the standards showed that the data were unreliable when samples were this weak. We measured total hemolymph protein in mg protein ml -1 hemolymph with a Total Protein Kit, Micro (Sigma) compared to a serial dilution of the human albumin standard. 2.4. Verifying Infection. An additional 1 0 pL of hemolymph collected as described above was smeared on a slide and stained with a drop of lactofuchsin. Hemolymph samples were scanned at 400x, using dark-field, phase-contrast microscopy, for hyphae and blastospores. 2.5. Statistical Analyses. To analyze the B. bassiana dose response data, we combined the data from both replicates because Fisher’s Exact Tests indicated no significant differ- ences between the replicates at each dose. The combined data Psyche 3 Table 1: Pathogenicity of Beauveria bassiana strain GHA for adult Anabrus simplex based on mortalities 21 days after topical application. LD50 (conidia/insect) 95% Confidence Limits (conidia/insect) Slope (S.E) Chi- Square g** (P)* 6.46 X 10 5 3.97 x 10 5 - 1.275 x 10 6 0.885 (0.171) 6.745 (.08) 0.144 * Chi-square of heterogeneity: measures goodness of fit to the weighted regression line with P > .05 indicating a good fit of the data to the line. D.F. = 5 **£ is the index of regression significance. were then subjected to probit analysis using LDP Line (LdP Line, 2000 by Ehab Mostofa Bakr, Cairo, Egypt). Lysozyme and logio-transformed PO were normally distributed. Apply- ing ANCOVA, we covaried the dependent variables with body mass and tested them for effects of replicate, sex and fungal dose (sample sizes in order of dosage from highest to lowest: n - 2, 8, 9, 10, 10, and 10 for the 1st replicate and n = 3, 5, 8, 6, 9, and 10 for the 2nd). Body mass was not a significant covariate, and so here we report the results from the three-way AN OVA’s. Only for the males did the total protein meet the assumptions for parametric statistical analyses, and so we applied nonparametric statistics to data for the females. Data for PO and total protein were normally distributed after logio transformations. Lysozyme activity was normally distributed after squaring the data. Applying ANCOVA, we covaried the dependent variables with body mass and tested them for effects of sex and fungal treatment. However, body mass was not a significant covariate, and so we simplified the analysis and reported the two-way AN OVA’s. (a) Ph 6 3.6 - QJ A =2 o 4 a 3.5 - •g j* £ j O c a a 3.4 - 3.3 - ^ c 2 bQ 3.2 - JO 3.1 - Control 51 113 354 1070 1750 Beauveria spore application (in thousands) (b) Figure 2: (a) Body mass and (b) phenoloxidase (PO) activity of adult Mormon crickets relative to the dose of Beauveria bassiana applied. Means and standard errors of the two replicates are shown with significantly different means in post hoc comparisons indicated by different letters. 3. Results Mortality at 21 days ranged from 22% to 80% and increased with the dose of B. bassiana applied to the cuticle (Table 1) with an LD50 estimate of 6.46 X 10 5 conidia per insect. For survivors, mean body masses of replicates were significantly different (P = .038), and those for all treatments except one were significantly less than that for controls, but there was no difference in body mass among B. bassiana doses (Figure 2(a)). Log PO differed significantly between replicates and dose (P = .0015 and P = .0048, resp.) whereas it did not differ between the sexes (P = .80). In a post hoc comparison among the means, Mormon crickets treated with B. bassiana had greater PO activity than uninfected controls, but none of the fungal treatments differed from one another (Figure 2(b)). The second replicate also had significantly greater lysozyme activity than the first (P = .030) whereas sex and dose did not have significant effects (P = .81 and P = .57, resp.). Within males, total protein was proportional to body mass (P < .0001), and insects in the second replicate had significantly greater total protein than those in the first (P = .0025, resp.), but fungal treatment was not a significant factor affecting total protein (P = .635). Females in the second replicate also had significantly greater total protein than those in the first replicate (Wilcoxon test, S = 423, z = 2.02, P = .043), but fungal treatment was not a significant factor affecting total protein within replicates (P > .60). 4. Discussion Mormon crickets responded to B. bassiana infection with an increase in PO. Beauveria infection also increased active PO levels in the grasshopper Melanoplus sanguinipes and the army cutworm Spodoptera exigua [12], Gillespie and Khachatourians [11] found that after topical application of 10 8 conidia to M. sanguinipes, PO levels increased 3.8 times in males peaking at 3 days postinfection and 8.3 times in females peaking on the first day postinfection. In M. sanguinipes after 5 days, PO levels had returned to near control levels in males, but in females remained more than twice that of controls. Our applied doses were lower, and more of the Mormon crickets survived the application. At 21 days, PO levels remained higher in Beauveria- treated Mormon crickets relative to controls. We did not observe a difference in PO levels between the sexes for either controls or those that survived fungal application. Surprisingly, PO titres of Beauveria- treated survivors were independent of the dose applied. 4 Psyche log PO | Infected I I Clear Figure 3: Phenoloxidase (PO) activity of survivors with fungal cells visible in their hemolymph (infected) and that of survivors with clear hemolymph. Inset: dark brown adult female Mormon cricket with white Beauveria sporulating on its cuticle. Total circulating protein concentrations did not differ between treatments in males or females. In Melanoplus sanguinipes, protein concentrations of males and females peaked 30% above that of controls within three days of infection, but returned to the same level as controls by day five post infection [11]. The second replicate had higher PO, lysozyme, and total protein titers than the first. Adults were collected from the same location on the same day and treated only a day apart to make replicates as similar as possible, and thus the reason for these differences is not known. Body mass of individuals did not differ significantly between control groups ( n = 20, P = .38), and so individuals in the second replicate were probably in no better overall condition to defend against the fungus than the first. Indeed, the average mass of the first replicate was 6% greater than that of the second replicate — the opposite of what one would expect if condition were a factor. Beauveria- treated individuals lost on average 17% of their mass relative to controls. Reduced food consumption is the most likely cause. Schistocerca gregaria eats less when infected with Metarhizium [15], and Manduca sexta stops feeding altogether [16]. However, an increase in metabolism with infection could also increase mass loss. Metabolic rate might increase because the Mormon cricket is fending off the infection or as a result of the contribution of the growing fungus. Reduced nutrient absorption from the gut or greater water loss might also contribute to mass loss and warrant further study. PO activity of survivors with fungal cells visible in their hemolymph did not differ significantly from those with clear hemolymph (n = 57 fungus absent, n - 9 fungus present, Welch ANOVA F = 0.06, d.f. = 1, 9, P = .81, Figure 3). We conclude that circulating PO may be an important enzymatic defense against Beauveria infection and that it is associated with attempted clearing of Beauveria blastospores and hyphae from the hemolymph of Mormon crickets. Beauveria bassiana infection did not affect lysozyme activity in the Mormon crickets. Hence, elevation of PO did not result in an elevation of antibacterial activity in an all- or-none manner. Lysozyme activity declined with Beauveria infection in the desert locust Schistocerca gregaria [10] but remained unchanged in the army cutworm Spodoptera exigua [13]. In some Mormon cricket bands, migrating individuals seek protein [3], and protein ingestion is associated with an increase in PO activity [17]. Thus, protein deficiency evident in migratory bands is also likely to result in greater susceptibility to and more efficacious application of B. bassiana GHA. Acknowledgments The authors thank Rob Schlothauser, USDA- Agricultural Research Services, for help with fungal infections and Laura Senior, USDA- Agricultural Research Services, for assistance with immunity assays. References [1] A. E. Hajek, “Ecology of terrestrial fungal entomopathogens,” Advances in Microbial Ecology, vol. 15, no. 1, pp. 193-249, 1999. [2] D. T. Gwynne, Katydids and Bushcrickets: Reproductive Behav- ior and Evolution of the Tettigoniidae, Cornell University Press, Ithaca, NY, USA, 2001. [3] S. J. Simpson, G. A. Sword, P. D. Lorch, and I. D. Couzin, “Cannibal crickets on a forced march for protein and salt,” Proceedings of the National Academy of Sciences of the United States of America, vol. 103, no. 11, pp. 4152-4156, 2006. [4] B.-D. Sun, H.-Y. Yu, A. J. Chen, and X.-Z. Liu, “Insect- associated fungi in soils of field crops and orchards,” Crop Protection, vol. 27, no. 11, pp. 1421-1426, 2008. [5] A. E. Hajek and R. J. Leger, “Interactions between fungal pathogens and insect hosts,” Annual Review of Entomology, vol. 39, pp. 293-322, 1994. [6] L. M. Mullen and G. J. Goldsworthy, “Immune responses of locusts to challenge with the pathogenic fungus Metarhizium or high doses of laminarin,” Journal of Insect Physiology, vol. 52, no. 4, pp. 389-398, 2006. [7] S. N. Gardner and M. B. Thomas, “Costs and benefits of fighting infection in locusts,” Evolutionary Ecology Research, vol. 4, no. 1, pp. 109-131, 2002. [8] K. Wilson, M. B. Thomas, S. Blanford, M. Doggett, S. J. Simpson, and S. L. Moore, “Coping with crowds: density- dependent disease resistance in desert locusts,” Proceedings of the National Academy of Sciences of the United States of America, vol. 99, no. 8, pp. 5471-5475, 2002. [9] J. H. Turnbow, Temperature-sensitive Beauveria bassiana myco- sis in the Mormon cricket, Anabrus simplex, M.S. thesis, Montana State University, Bozeman, MT, USA, 1998. [10] J. P. Gillespie, C. Burnett, and A. K. Charnley, “The immune response of the desert locust Schistocerca gregaria during mycosis of the entomopathogenic fungus, Metarhizium aniso- pliae var acridumf Journal of Insect Physiology, vol. 46, no. 4, pp. 429-437, 2000. [11] J. P. Gillespie and G. G. Khachatourians, “Characterization of the Melanoplus sanguinipes hemolymph after infection with Beauveria bassiana or wounding,” Comparative Biochemistry and Physiology B, vol. 103, no. 2, pp. 455-463, 1992. Psyche 5 [12] S. Y. Hung and D. G. Boucias, “Phenoloxidase activity in Hemolymph of Naive and Beauveria bassiana- infected Spodoptera exigua Larvae,” Journal of Invertebrate Pathology , vol. 67, no. 1, pp. 35-40, 1996. [ 13] D. G. Boucias, S. Y. Hung, I. Mazet, and J. Azbell, “Effect of the fungal pathogen, Beauveria bassiana , on the lysozyme activity in Spodoptera exigua larvae,” Journal of Insect Physiology, vol. 40, no. 5, pp. 385-391, 1994. [14] P. de Azambuja, E. S. Garcia, N. A. Ratcliffe, and J. David Warthen Jr., “Immune-depression in Rhodnius prolixus induced by the growth inhibitor, Azadirachtin,” Journal of Insect Physiology, vol. 37, no. 10, pp. 771-777, 1991. [15] E. Seyoum, D. Moore, and A. K. Charnley, “Reduction in flight activity and food consumption by the desert locust, Schisto- cerca gregaria, after infection with Metarhizium flavoviride,” Zeitschrift fur Angewandte Entomologie, vol. 118, no. 3, pp. 310-315, 1994. [16] P. Dean, J. C. Gadsden, E. H. Richards, J. P. Edwards, A. K. Charnley, and S. E. Reynolds, “Modulation by eicosanoid biosynthesis inhibitors of immune responses by the insect Manduca sexta to the pathogenic fungus Metarhizium aniso- pliaef Journal of Invertebrate Pathology, vol. 79, no. 2, pp. 93- 101 , 2002 . [17] R. B. Srygley, P. D. Lorch, S. J. Simpson, and G. A. Sword, “Immediate protein dietary effects on movement and the generalised immunocompetence of migrating Mormon crick- ets Anabrus simplex (Orthoptera: Tettigoniidae),” Ecological Entomology, vol. 34, no. 5, pp. 663-668, 2009. Hindawi Publishing Corporation Psyche Volume 2011, Article ID 459315, 9 pages doi: 10. 1 155/20 1 1/4593 15 Research Article Diel Behavioral Activity Patterns in Adult Solitarious Desert Locust, Schistocerca gregaria (Forskal) Sidi Ould Ely, 1,2 Peter G. N. Njagi, 1 Magzoub Omer Bashir, 3,4 Salah El-Tom El-Amin, 4 and Ahmed Hassanali 1,5 1 International Centre of Insect Physiology and Ecology (ICIPE), P.O. Box 30772-00100, Nairobi, Kenya 2 Centre National de Lutte Antiacridienne, BP 665 Nouakchott, Mauritania 3 ICIPE Field Station, P.O. Box 1213, Port Sudan, Sudan 4 Crop Protection, Faculty of Agriculture, Department of Crop Protection, University of Khartoum, P.O. Box 32, Khartoum North, Shambat, Sudan 5 Chemistry Department, Kenyatta University, P.O. Box 43844-00100, Nairobi, Kenya Correspondence should be addressed to Sidi Ould Ely, sidiouldely@yahoo.com Received 20 March 2010; Revised 5 June 2010; Accepted 19 August 2010 Academic Editor: Gregory A. Sword Copyright © 201 1 Sidi Ould Ely et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. The responses of adult solitarious desert locust to odors from a host plant were evaluated in a two-choice wind tunnel. Solitarious desert locusts collected from the held (Red Sea Coast) were more attracted to volatiles from potted Heliotropium ovalifolium in scotophase than in photophase. The attraction towards the host plant odors rather than to clean air, in both photophase and scotophase, concurs with previous observations on oviposition preferences near these plants. Diel behavioral activity patterns of adult solitarious desert locusts Schistocerca gregaria (Forskal) that were collected from the held in Port Sudan were investigated by monitoring, scanning, resting, taking off, and walking/running in a wind tunnel. Solitarious locusts that had been propagated in the laboratory for 20 generations were also observed for comparison. In both groups of locusts, insects were signihcantly more active after sunset and this activity attained peak level at 1-2 hours after dusk. Of the two groups, solitarious locusts collected from the held were signihcantly more active. In the scotophase, the former traversed distances that were about seven times those covered by laboratory-reared locusts. Overall, the results show that the repertoire of behavioral activities of solitarious locusts is maintained in laboratory-reared insects, albeit at a lower level. The implications of these observations in the behavioral ecology of the desert locust are discussed. 1. Introduction Among the two phases (solitarious and gregarious) of the desert locust, Schistocerca gregaria (Forskal), the active solitarious locusts are primarily present during long drought periods and are mainly confined to some patchy habitats of the arid areas in the Sahel [1, 2]. A number of held observa- tions on solitarious locusts suggest nocturnal behavior of this phase of the insect. They have been reported to be cryptic during the day, spending more time either resting on the ground or roosting within bushes and only fly when they are disturbed or flushed [3]. On the other hand, in warm weather, they have been reported to start flying after dusk and continue being active during the early part of the night [4]. These night flights sometimes culminate into migrations of the solitarious locusts into distant habitats in swarms, like their gregarious counterparts, leading to unexpected locust infestations, and it has been suggested that they can fly distances of up to 1000 km [5-9]. There are also reports on seasonal movements of solitarious locusts between summer breeding areas in the Sahelian zone and winter-spring breeding habitats in the southern and central Sahara [10- 15]. More recently, Riley and Reynolds [16] made an attempt to monitor migrating solitarious individuals flying at high altitudes at night using vertical-looking radar (VLR). Flost plants contribute significantly to locust and grasshopper dynamics because of dietary relationship between preferred host plants and grasshopper survival, 2 Psyche growth, and reproductive performance [17]. Moreover, preference for specific desert plants for oviposition is envisaged to play a significant role in initiating congre- gation of scattered solitarious locusts in the field [4, 18- 21 ]. However, no definitive studies associated with the diel behavioral patterns of solitarious desert locusts have been reported, unlike gregarious locusts on which extensive information is available. Methodical attempts to address this gap are an important prerequisite for understanding the behavioral and population dynamics of the solitarious phase and, therefore, the subtleties that underlie the phase dynamics of the insect. In the present study, we examined the behavioral re- sponses (scanning, resting/walking/running, flying attempts, and distance moved) of field caught solitarious desert locusts that were exposed to odor plumes originating from potted Heliotropium ovalifolium during photophase and scotophase (artificially induced). The activity patterns of these insects were also monitored in detail in the laboratory. For com- parison, we also studied the behavioral patterns of isolated locusts that had been reared in our laboratory for many generations. 2. Materials and Methods 2.1. Insects. Solitarious desert locusts aged between 3 and 4 weeks old were collected from the field around the Tokkar Delta on the Red Sea Coast of Sudan. Each locust was kept isolated in a 1L ice cream cup for about one week to adapt to the laboratory conditions prior to carrying out the obser- vations. Each cup was ventilated through a small window in the lid that was covered with a piece of fine gauze. For comparison, 24-day-old solitary-reared locusts that had been kept in the laboratory for 20 generations (corresponding to five years) and fed on a mixture of desert plants at the ICIPE field station, Port Sudan were used. Both groups of locusts were kept in a room maintained at the ambient temperature and humidity and a 12L : 12D photoperiod which is roughly the same as in natural conditions at Port Sudan. 2.2. Wind Tunnel. The behavior of locusts was observed in a rectangular flat -bed wind tunnel (110 X 40 x 40 cm) made of clear Plexiglas for easy observation and to minimize the tendency of insects to climb up the walls (Figure 1 ) . The wind tunnel had two openings (15 cm X 15 cm) with covers on the top side for the placement or removal of locusts. At the bottom of each end, a rectangular opening (25 cm X 2 cm) which was covered with a black muslin cloth formed the air inlet. Air was drawn into the wind tunnel and cleaned using activated charcoal (granular, 4-14 mesh; Sigma Chemical Co.) filters that lined up the air inlets. Subsequent extraction of the air was through a central port (10 cm X 2 cm) in the floor of the wind tunnel that was connected to an exhaust fan via a duct. The air speed recorded 1-2 cm above the floor of the wind tunnel during observations was 15-20 cm/s. When using potted plants ( Heliotropium ovalifolium), small chambers (25cmW X 2 cm H X 5cmL) were replaced by bigger chambers (25 X 25 X 25 cm) that could fit the potted plant (Figure 1). Plants were hidden from insects tested by black sugar paper. 2.3. Behavioral Assays. Observations were carried out during photophase (10:00 h-16:00h) and after sunset during sco- tophase (19:00 h-23:00 h) in Port Sudan. In experiments that were carried out in photophase, five 60 -watt bulbs placed one meter directly above the wind tunnel illuminated the experimental section and there were no other sources of light in the room. An electric fan heater with a thermostat maintained the room temperature at a level similar to that recorded outdoors in sunshine (31.7 ± 3°C) during the day and 27.3 ± 1.2°C at night. The relative humidity was 55.1 ± 1.5% and 65.0 ± 3.9%, respectively. At the end of the day, the fan heater was switched off one hour earlier after opening windows of the bioassay room to allow for the equilibration of the indoor temperature with the one outside. Lights were also switched off and observations carried out with the aid of an Infrared Find-R scope viewing device (FJW Optical Systems Inc., USA). An additional 5 -watt red lamp was placed over the wind tunnel to moderate the darkness in the room. A solitarious male or female locust was held in a small perforated Plexiglas cage (10 cm X 4 cm X 4 cm) that had no base placed over the wire mesh covering the central exhaust port on the floor of the tunnel (Figure 1). The holding cage had a nylon string (4 mm thick) attached to the top and running through a small hole (5 mm diameter) in the top of the wind tunnel. The test insect was held under the cage for 2-3 minutes to allow it to acclimatize and the air evacuation system was switched on prior to starting the observations. To release the insect, the holding cage was pulled up and secured using the nylon string and the locust was then free to move toward the middle of the wind tunnel. The following behaviors of each locust from the two groups were monitored by the same person over the subsequent 30 minutes: (i) scanning — movement of the front part of the body from side to side (^4-6° displacement) with the body anchored by the abdominal tip (these movements have been suggested to be important in estimating the distance to the nearest visible object in the insect’s field of vision [22-24]); (ii) flight attempts — these were vigorous jumps that were presumed to represent onset of flight that was, however, curtailed by the walls of the wind tunnel; (iii) walking and the distance traversed — no attempt was made to evaluate the speed of the movement; (iv) resting — characterized by a locust that did not change position for 5 seconds or more; (v) mean distance traversed towards the plant source when potted H. ovalifolium was included. The data were recorded as either the proportion of insects performing a given behavior and/or the frequency of occurrence of the behavior. Each locust was tested only once and 40 males and 40 females of each group were observed (laboratoryreared and field-collected locusts). Occurrence of the behaviors and their frequencies were recorded using The Observer 3.0 (Noldus Information Technology BV. Wageningen, Netherlands). Psyche 3 Figure 1: Diagram of the flat-bed wind tunnel used for testing plant volatiles, (a) Side view of the full length, (b) Top view. 1) Exhaust fan; 2) Cylindrical duct; 3) Wind tunnel chamber (transparent perpex); 4) Test insect holding box; 5) Doors for introduction and collection of insects; 6) Cord for pulling the insect box up; 7) Section for holding plant; 8) Potted desert plant; 9) activated charcoal filter; 10) wire mesh strip for air outlet; 11) wire mesh strip for air inlets; 12) Fan speed controller. Table 1: Comparison of overall means (±SE) frequencies of walking, scanning, and jumping per insect for locusts caught from field in presence and absence of host plant {Heliotr opium sp.) stimulus in photo- and scotophase. N = 80 insects used for each of the three behaviors. Behavioral activity (frequency of occurrence/insect) Scanning Jumping Walking Sex Stimuli Photophase Scotophase Photophase Scotophase Photophase Scotophase Males None 25.7 ± 2.4 a 47.5 ± 3.4 ab 4.5 ± l.l a 15.3 ± 2.8 a 21.8 ± 2.3 a 43.3 ± 2.9 a Females None 20.5 ± 1.6 ab 39.9 ± 3.4 a 1.8 ± 0.7 b 4.4 ± 1.4 C 16.9 ± 1.5 bc 37.0 ± 3.0 ab Males Host plant 30.9 ± 4.5 a 45.9 ± 3.8 ab 4.9 ± 1.2 a 26.2 ± 4.3 b 37.9 ± 5.2 b 47.9 ± 4.8 a Females Host plant 23.2 ± 4.3 b 52.1 ±4.8 b 3.9 ± l.l ab 3.4 ± 0.7 C 15.8 ±2.8° 32.8 ±4. 7 b Means with the same superscript letter in each column for each behavior are not significantly different (LSD test, P < .05). 2.4. Statistical Analysis. Data were analyzed using SAS (SAS Institute Inc., V 8.02, Cary, North Carolina, USA). For the wind tunnel experiments, separation of means of the frequencies of the behaviors studied between the laboratory- reared and field-collected solitarious locusts was carried out using Least Significance Difference (LSD) test for equal replications (P < .05). Student-Newman-Keuls multiple range test at P < .05 was used to analyze behavioral activity of solitarious locusts from the field. Tukey’s studentized range test, at P < .05, was used to compare distance traversed by locusts during photo- and scotophases. The comparative behavior of lab and field locusts was analyzed using Student- Neuman-Kuels multiple range test, P < .05. The Student’s t- test was used to evaluate differences between photophase and scotophase while the y 2 test was applied to determine the sig- nificance in the proportion of insects attempting to take off. 3. Results 3. 1 . Behavior of Solitarious Locusts from the Field in Presence of Potted Host Plant. Males showed significantly more activity in the presence of host plant odors during scotophase relative to photophase compared to females, which showed less activity (Table 1, Figure 5). The mean distance traversed and the proportion of males and females that reached the target were recorded (Table 2); both sexes traversed significantly greater distance toward the source of stimulus compared to the clean air side and a significant proportion of these reached the source (Table 2). 3.2. General Behavioral Activity of Solitarious Locusts from the Field. Solitarious locusts that had been caught from the field and kept under laboratory conditions for a week were mainly more active after dusk than during the day or later hours in the night. After dusk, there was a considerable increase in the frequency of scanning, jumping, and walking for both male and female locusts within the first two hours after sunset and a subsequent decline in the activity of the insects (Figures 2(a)-2(c), 3(a)— 3(c)). In photophase, most of the insects remained static or executed very limited movement (Figures 2(a)-2(c), 3(a)-3(c)). This is also reflected by the distance traversed by the insects which was highly significant (Tukey’s studentized range test, P < .05) after dusk than in photophase (Figure 4(a)). However, there was a notable difference between male and female locusts with the males having significantly higher (Tukey’s test, P < .05) activity than the females at night. Furthermore, ca. 74% of the locusts attempted to take off within the first 5 minutes of the 30 min observation period after dusk. This was significantly higher {y 1 = 30.66, P < .0001) than in photophase, during which only 30% of the insects made the attempts over a similar period (Figure 4(b)). Furthermore, some locusts did not attempt to take off at all during the observation period. Only 12.5% of the insects failed to take off during night observations while a 4 Psyche o T 10:00 11:00 12:00 19:00 20:00 21:00 13:00 14:00 22:00 23:00 Time of day Time of day (a) (d) 10:00 19:00 11:00 20:00 12:00 21:00 13:00 22:00 14:00 23:00 Time of day Time of day (b) (e) 0 T 1 10:00 11:00 12:00 19:00 20:00 21:00 13:00 14:00 22:00 23:00 Time of day Time of day ♦ Scotophase O Photophase ♦ Scotophase O Photophase (c) (f) Figure 2: Activity of mature field-collected ((a)-(c)) and laboratory- reared ((d)-(f)) solitarious males. Bars represent standard errors (±SE); N = 80 insects used for each of the three behaviors. Psyche 5 10:00 19:00 11:00 20:00 12:00 21:00 13:00 22:00 14:00 23:00 Time of day Time of day (a) (d) Time of day Time of day (b) (e) 0 T 1 10:00 11:00 12:00 19:00 20:00 21:00 13:00 14:00 22:00 23:00 Time of day Time of day ♦ Scotophase O Photophase ♦ Scotophase o Photophase (c) (f) Figure 3: Activity of mature field-collected ((a)-(c)) and laboratory- reared ((d)-(f)) solitarious females. Bars represent standard errors (±SE); N = 80 insects used for each of the three behaviors. 6 Psyche Lab-reared insects Field-collected insects □ Photophase □ Scotophase □ Photophase □ Scotophase (a) (b) -p O' G a o CO 5-h +-> O G O U Males Females No stimuli Males Females Plant odor (a) (b) 100 o a C 3 *c3 & _ .05). significantly higher (^ 2 = 16.82; P < .0001) proportion («41%) was recorded during photophase (Figure 4(c)). 3.3. Comparative Behavior of Laboratory-Reared Locusts. Solitarious locusts that had been kept in our laboratory’s rearing unit for 20 generations had similar behavioral patterns to those of locusts collected from the field but the activity levels were much lower. In addition, the behavioral patterns of male and female laboratory locusts in photophase and after dusk were very similar (Figures 2(d)-2(f), 3(d)- 3(f)). Frequencies of the behaviors monitored (scanning, jumping and walking) and the distance moved were significantly higher at the onset of dusk (especially the first two hours after sunset) than during daytime. The locusts also traversed significantly longer (Tukey’s studentized range test, P < .05) distance after dusk (Figure 4(a)). In addition, a significantly higher (y 2 = 28.6; P < .001) proportion («54%) of the locusts attempted to take off in the first five minutes of the observation period compared to 14% in photophase (Figure 4(b)). Furthermore, throughout the observation period, 52% of the locusts did not take off during the day while only 20% (y 2 = 8.35; P < .01) failed to take off after dusk (Figure 4(c)). Thus, behavioral patterns of the two groups of solitarious insects were similar, although both male and female locusts caught from the field were significantly more active (Tukey’s studentized range test, P < .05) and traversed about seven times the distance covered by the laboratory- reared insects after dusk (Figure 4(a)). 8 Psyche 4. Discussion In order to obtain a better understanding of the behav- ior and biology of Schistocerca gregaria populations, it is important to understand their interactions with host plants and their habitats. Kairomones are interspecific chemical cues, which may mediate host plant seeking and host acceptance behavior by locusts; they may also play a role in physiological predisposition of solitarious locusts to the gregarious phase [25]. Two groups of kairomones may influence the behavior of locusts; odors of host plants which play a role in the location of food [25, 26], and nonvolatile allelochemics involved in food selection [27]. Observations on field- collected solitarious locusts in the present study confirm that both sexes of this phase are attracted to volatiles emanating from H. ovalifolium, previously shown to be a preferred plant for oviposition and feeding by solitarious phase desert locusts in the field [19, 20]. However, the response of the insect was much more pronounced in the scotophase. Diel periodicity in the behavior of some species of acridids has been observed in the field [4, 7, 11, 28, 29], but no detailed laboratory or field studies have been carried out. The present results from our laboratory observations show that solitarious desert locusts, S. gregaria, are more active after dusk than during daytime. The results also conform to the documented field observations that solitarious locusts are largely immobile throughout the day and only start flying after sunset [3]. The low frequencies of walking (and the distance traversed) and attempts to take off by both male and female locusts at daytime reflect the inactivity of solitarious locusts during the day. In the field, solitarious locusts start taking off 20-30 minutes after sunset. The flight activity reaches peak and then declines within the next 3 hrs [4, 7, 9, 1 1, 28, 29]. What triggers the onset of the high behavioral activity of the solitarious locusts after sunset? M.A. Volkon- sky and M.T. Volkonsky [12] and Waloff [8] suggested that it may be induced by the sudden drop in light intensity. Roffey [9] observed that solitarious locusts apparently started taking off without any prior disturbance at evenings when the light intensity decreased from 400 to 3.5 lux. The compound eyes of solitarious locusts are structurally suitable for vision under subdued light and are sensitive to movements rather than sharp images [30]. Thus, solitarious adult locusts would be expected to be less active in bright sunlight during the daytime as opposed to their gregarious counterparts whose compound eyes are suited for diurnal vision. In daytime, solitarious locusts spend most of the time either resting on the ground or roosting within plant bushes [3]. Low behavioral activity during daytime may also aid crypsis which is adaptively used by solitarious desert locusts to min- imize predatory pressure by birds, which are mainly daytime hunters [3]. Birds are the major predators of desert locusts, both the adults in swarms and nymphs in hopper bands. In the wind tunnel observations carried out after sun- set, locusts scanned their field of vision and walked at significantly higher frequencies than during the day. Take- off attempts were also more frequent, in particular during the first two hours of the night although this activity was significantly higher throughout the night observation period than in daytime. While the diel behavioral patterns in the two groups of locusts were similar, locusts collected from the field were overall more active than those maintained in the rearing facility. These differences may be due to a set of interacting internal factors such as muscle development and the levels of energy reserves in individual insects [31]. These may in turn be dependent on the rearing conditions and other external factors that the locusts are exposed to. For example, in the laboratory, confinement in small cages used for rearing isolated locusts limits their walking movements and makes them unable to execute any flights. This might stress the insects and may lead to underdevelopment of flight muscles in the insects as opposed to their field counterparts that undertake short distance and migratory flights [5-9]. In addition, environmental factors such as temperature and relative humidity under which the locusts are reared and kept may also play a role. In the laboratory, locusts are generally reared under constant controlled temperatures while in the field they are exposed to fluctuating temperatures and humidity [32]. In the field, large-scale night flights have been observed to occur when air temperatures are equal to or greater than 24°C [5, 10]. Another external factor which may influence the level of behavioral activity of the locusts is food quality which largely determines their energy reserves necessary for flight and other behaviors [31]. In conclusion, the results of this study confirm previous field observations that solitarious desert locusts are more behaviorally active after onset of dusk than during day. This is manifested as short distance and migratory flights in the field after sunset. While the diel behavioral patterns are preserved in the laboratory-reared solitarious locusts, it was evident that there is a significant decline in the levels of behavioral activities after several generations. We suggest that, where possible, insects freshly caught from the field are most suitable for use in bioassays aimed at evaluating and understanding various behaviors of the solitarious desert locust. Acknowledgments This work was supported by The Program for Co-operation with International Institutes (SII), formerly DSO, and The Swiss Agency for Development and Cooperation (SDC) through FAO, to which the authors are most grateful. The assistance provided by Messrs. Hayder Hanan Korena and Abdelrahim Widatalla Bashir, ICIPE’s Field Station, Port Sudan in rearing the locusts and various assistance is appreciated. References [1] B. P. Uvarov, “A revision for the genus Locusta L. (=Pachytylus Fieb. ), with a new theory as to the periodicity and migrations of locusts,” Bulletin of Entomological Research, vol. 12, pp. 135— 163, 1921. [2] J. Roffey, “The Desert Locust upsurge and its termination 1977-79,” in Field Research Stations, Technical Series, no. AGP/DL/TS/23, pp. 1-74, FAO, Rome, Italy, 1982. Psyche 9 [3] A. Steedman, Ed., Locust Handbook, Overseas Development Natural Resource Institute, London, UK, 2nd edition, 1988. [4] J. Roffey and G. Popov, “Environmental and behavioural processes in a desert locust outbreak,” Nature, vol. 219, no. 5153, pp. 446-450, 1968. [5] Y. R. 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Hindawi Publishing Corporation Psyche Volume 201 1, Article ID 980372, 9 pages doi:10.1 155/201 1/980372 Research Article Application of General Circulation Models to Assess the Potential Impact of Climate Change on Potential Distribution and Relative Abundance of Melanoplus sanguinipes (Fabricius) (Orthoptera: Acrididae) in North America O. Olfert, 1 R. M. Weiss, 1 and D. Kriticos 2 Agriculture and Agri-Food Canada, Saskatoon Research Centre, 107 Science Place, Saskatoon, SK, Canada S7N 0X2 2 CSIRO Entomology, GPO Box 1700, Canberra, ACT 2601, Australia Correspondence should be addressed to O. Olfert, owen.olfert@agr.gc.ca Received 1 June 2010; Revised 6 August 2010; Accepted 7 August 2010 Academic Editor: Michel Lecoq Copyright © 2011 O. Olfert etal. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Climate is the dominant factor determining the distribution and abundance of most insect species. In recent years, the issue of climatic changes caused by human activities and the effects on agriculture has raised concern. General circulation model scenarios were applied to a bioclimatic model of Melanoplus sanguinipes to assess the potential impact of global warming on its distribution and relative abundance. Native to North America and widely distributed, M. sanguinipes is one of the grasshopper species of the continent most responsible for economic damage to grain, oilseed, pulse, and forage crops. Compared to predicted range and distribution under current climate conditions, model results indicated that M sanguinipes would have increased range and relative abundance under the three general circulation model scenarios in more northern regions of North America. Conversely, model output predicted that the range of this crop pest could contract in regions where climate conditions became limiting. 1. Introduction Climate is the dominant factor determining the distribution and abundance of most insect species [1]. The issue of climatic changes caused by human activities and the effects on agriculture has raised concern in recent years. The overall global temperature has increased 0.7°C over the last 100 years, with the 1990’s being the warmest decade on record [2] . Climate change scenarios using low greenhouse gas emissions suggest that temperatures will increase by 1-3 °C over the next 100 years and temperatures have been predicted to increase by 3.5-7. 5° C for scenarios with high gas emission [3] . However, Walther et al. [4] suggest that species respond to regional changes that are highly heterogeneous and not to approximated global averages. Many species have already responded to regional conditions that have occurred during the 20th century. In a study of 694 animal and plant species, Root et al. [5] investigated the change in timing of events over the past 50 years and reported that changes in timing of spring events (breeding, blooming) occurred 5.1 days earlier per decade. Warming conditions may impact grasshopper populations by extending the growing season, altering the timing of emergence from overwintering sites, increasing growth and development rates, shorting generation times, increasing the numbers of eggs laid, and changing their geographic distribution [6, 7]. Analogue scenarios which make use of existing climate data are useful to identify geographic regions that may be susceptible to establishment of insects, when comparing the results of climate change scenarios to those regions where the species in question is already established [8]. However, the magnitude of predicted temperature change associated with climate change is not within the historical experience of modern agriculture. Hence, it is unlikely that we can use historical data as analogues to predict the impact of climate change on pest species. As a result, simulation models have been used to assess impact and related system vulnerability due to climate change. 2 Psyche Table 1: CLIMEX parameter values used to predict potential distribution and relative abundance of Melanoplus sanguinipes in North America. CLIMEX growth parameters Temperature DV0 Limiting low average weekly temperature 10.0°C DV1 Lower optimal average weekly minimum temperature 16.0°C DV2 Upper optimal average weekly maximum temperature 28.0°C DV3 Limiting high average weekly maximum temperature 32.0°C Moisture SM0 Limiting low soil moisture 0.02 SMI Lower optimal soil moisture 0.05 SM2 Upper optimal soil moisture 0.30 SM3 Limiting high soil moisture 0.70 Diapause DPD0 Diapause induction day length 11 h DPT0 Diapause induction temperature (average weekly minimum) 11.0°C DPD1 Diapause termination temperature (average weekly minimum) 3.0°C DPD Diapause development days 120 DPSW Summer or winter diapause 0 CLIMEX Stress Parameters: Cold stress TTCS Cold stress threshold (average weekly minimum temperature) -18.0°C THCS Rate of cold stress accumulation -0.0004 Heat stress TTHS Heat stress threshold (mean weekly maximum temperature) 35.0°C THHS Rate of heat stress accumulation 0.008 Dry stress SMDS Dry stress threshold (mean weekly minimum soil moisture) 0.020 HDS Rate of dry stress accumulation -0.003 Wet stress SMWS Wet stress threshold (mean weekly maximum soil moisture) 0.7 HWS Rate of wet stress accumulation 0.001 Bioclimate simulation models have been used success- fully to predict the distribution and extent of insect estab- lishment in new environments [9-12]. Bioclimatic modeling software, such as CLIMEX, enables the development of models that describe the potential distribution and relative abundance of a species based on climate [1, 13]. CLIMEX derives an Ecoclimatic Index (El) which describes the suitability of specific locations for species survival and reproduction. Model parameters include temperature (TI), diapause (DI), light (LI), moisture (MI), heat stress (HS), cold stress (CS), wet stress (WS), and dry stress (DS). The El values are obtained by combining a Growth Index (GI) with stress indices (dry, wet, cold, and hot) that describe conditions that are unfavourable for growth. Native to North America and widely distributed, Melanoplus sanguinipes (Fabricius) (Orthoptera: Acrididae) is responsible for more economic damage to grain, oilseed, pulse, and forage crops than any other grasshopper species [14-16]. A bioclimate model was developed to predict the potential distribution and relative abundance of M. san- guinipes, within Canada [17]. Ecological sensitivity analyses were then conducted using incremental scenarios for all combinations of temperature (0, +1, +2, +3, +4, +5, +6, and +7°C of climate normal temperature for each grid) and of precipitation (-60%, -40%, -20%, -10%, 0%, 10%, 20%, 40%, 60% of climate normal precipitation for each grid). Compared to predicted range and distribution under current climate conditions, model results indicated that AL. sanguinipes would have increased range and relative abundance for temperature increases between 1°C and 7°C. The model predicted that the range of this crop pest could be extended to regions that are not currently used for agricultural production in North America. Mika et al. [18] stated that at an ecosystem level, climatic variables will vary both spatially and temporally. Therefore, they suggested that the widely accepted and more commonly used general circulation models (GCMs) should be used in conjunction with bioclimate models, rather than incremental scenarios. Further, they encouraged the application of multiple GCMs due to the variability of climate projections between models. The objective of this study was to use the bioclimate model for M. sanguinipes [17] to assess the impact of three Psyche 3 Table 2: Baseline(CRU) and general circulation model (NCAR273 CCSM, MIROC-H, CSIRO MARK 3.0) scenarios and resulting Ecoclimatic Inex (El), temperature (TI), moisture (MI), diapause (DI), growth index (GI), cold stress (CS), heat stress (HS), number of weeks GI was positive (Weeks GI Positive), and core distribution, for Melanoplus sanguinipes at six locations. Location Scenario El TI MI DI GI CS HS Weeks GI positive Core distribution Fairbanks, AK NCAR273 CCSM 20.1 22.3 83.2 38.5 20.7 2.9 0 18.2 97 CSIRO MARK 3.0 18.3 22.9 83.2 40.1 20.9 12.7 0 18 87.1 MIROC-H 18.2 21.5 87.3 37.7 20 8.6 0 17.1 91.3 CRU 5.4 12 88.6 33.1 11.1 54.2 0 13.9 45.7 Peace River, AB NCAR273 CCSM 23.8 34.2 71.9 42.1 23.8 0 0 20.7 97.3 CSIRO MARK 3.0 29.2 33.2 77.9 43.4 29.4 0.1 0 22.4 98.8 MIROC-H 25 30.2 79.5 41.3 25 0 0 21.2 98.6 CRU 14.7 21.8 80.2 36.9 16.5 9.6 0 19 87.9 Saskatoon, SK NCAR273 CCSM 34.9 37.8 92.3 45.6 34.9 0 0 23.8 100 CSIRO MARK 3.0 36.3 37.5 94.3 46.5 36.3 0 0 24.2 100 MIROC-H 35.2 36.6 91.7 44.6 35.2 0 0 23.3 100 CRU 26.7 30.7 96.1 41.8 28.8 8.2 0 21.8 91.8 Gillette, WY NCAR273 CCSM 24.4 29.9 96.9 48.8 24.4 0 0 19.7 100 CSIRO MARK 3.0 24.1 30.1 98.2 50.2 24.9 0 3.9 18.3 96.1 MIROC-H 24.9 30.4 95.8 47.1 24.9 0 0 20 100 CRU 31.7 35.2 98.5 44 31.7 0 0 23 100 Lincoln, NE NCAR273 CCSM 10.8 31.6 64 55.8 11.3 0 2.6 14.4 95.9 CSIRO MARK 3.0 12.2 28.6 91.7 57.2 18.8 0 40.8 16.7 65.7 MIROC-H 15.9 30.3 77.6 54.5 16.3 0 1.9 18.8 98.1 CRU 21.3 39 70.3 52.5 21.3 0 0 24.3 100 Lubbock, TX NCAR273 CCSM 14.1 37.4 96.2 43.7 18.1 0 50.1 13.8 58.3 CSIRO MARK 3.0 5.2 34.8 98.6 44.2 15.5 0 167.7 11.5 21 MIROC-H 9.5 33.9 97.5 47.3 17.9 0 95 13.4 40.2 CRU 30.6 39.3 98.7 57.1 31.1 0 1.6 22.1 98.4 general circulation models on population distribution and relative abundance across North America. 2. Methods The bioclimatic model for M. sanguinipes, developed using CLIMEX 2.0 [19], has been previously described [17]. CLIMEX is a dynamic model that integrates the weekly responses of a population to climate using a series of annual indices. It uses an annual Growth Index to describe the potential for population growth as a function of soil moisture and temperature during favourable conditions, and Stress Indices (cold, wet, hot, and dry) to determine the effect of abiotic stress on survival in unfavourable conditions. The weekly Growth Index is a function of temperature (TI), dia- pause (DI), and moisture (MI). The growth and stress indices are calculated weekly and then combined into an overall annual index of climatic suitability, the Ecoclimatic Index (El), that ranges from 0 for locations at which the species is not able to persist to 100 for locations that are optimal for the species [17]. Model parameter values are listed in Table 1 . Initial parameter values were obtained from published papers. Model parameters were then adjusted to ensure that El > 30 in geographical regions historically affected by M. sanguinipes, indicating that climatic conditions were favorable for development of densities associated with crop loss. Historical grasshopper population data were used for model validation. Annual surveys of abundance of adult grasshoppers have been conducted in Saskatchewan since 1931 [20]. Relative abundance was validated by comparison with adult grasshopper survey data from Saskatchewan over the period of 1970 to 2004 [17]. The model was tested by comparing the occurrence of observed life history events against those predicted by the model. Climate change projections were obtained from the Intergovernmental Panel on Climate Change [21 ] as monthly means for three GCMs, based on current climate, 30 yr aver- age (1961-1990) dataset (A1B emission scenario) (CRU — Climate Research Unit, East Anglia, UK). The three GCMs selected were CSIRO Mark 3.0 (CSIRO, Australia), NCAR273 CCSM (National Centre for Atmospheric Research, USA), and MIROC-H (Centre for Climate Research, Japan). All three had relatively small horizontal grid spacing and the requisite climatic variables at a temporal resolution appropriate for CLIMEX. The data were pattern-scaled to develop individual change scenarios relative to the base 4 Psyche Figure 1: Predicted distribution and abundance (El) of Melanoplus sanguinipes for current climate (CRU) at six regions: (A) Lubbock, TX; (B) Lincoln, NE; (C) Gillette, WY; (D) Saskatoon, SK; (E) Peace River, AB; (F) Fairbanks, AK. Green = “Unfavourable” (El = 0-5); Tan = “Suitable” (El = 5-20); Orange = “Favourable” (El = 20-30); Red = “Very Favourable” (El > 30). climatology [22]. The three models cover a range of climate sensitivity, defined as the amount of global warming for a doubling of the atmospheric CO 2 concentration compared with 1990 levels [23]. The respective sensitivities are: CSIRO Mark 3.0 (2.11°C), NCAR-CCSM (2.47°C), and MIROC-H (4.13°C). The resulting database was queried to analyze data at a regional scale. A geographic rectangle, 4° latitude by 7° longitude, was used to delineate a regional template. The defined region was approximately the size and shape of Colorado (270,000 km 2 ) and, for each of the datasets, consists of 112 grid cells. Specific regions, based on lati- tude and longitude coordinates, were defined and output (averaged across the region) was generated for detailed analysis. The datasets permitted comparison of variables, both spatially and temporally (weekly intervals). Analyses were based on values centered on six locations includ- ing Lubbock, Texas (33.6°N, 101. 9°W), Gillette, Wyoming (44.3°N, 105. 5°W), Lincoln, Nebraska (40.9°N, 96.7°W), Saskatoon, Saskatchewan (52.1°N, 106.6° W), Peace River, Alberta (56.2°N, 117.3°W), and Fairbanks, Alaska (64.8°N, 147.7°W). Contour maps were generated by importing El values into geographic information system software, ArcView 8.1 [24]. Final El values were displayed in the four categories defined above: “Unfavourable,” “Suitable;” “Favourable;” and “Very Favourable.” 3. Results and Discussion Comparisons were made to determine if differences in baseline climate data would result in differences in output. The New et al. [25] climate data represents a splined 0.5° world grid dataset. The El output the baseline CRU data agreed with that produced using the New et al. [25] climate data set in Olfert and Weiss [17]. Initially, there appeared to be some differences in model output between the two approaches for Peace River and Saskatoon (Table 2). Olfert and Weiss [17] reported that the El values for Peace River and Saskatoon were 24 and 30, respectively. This study showed that El values for Peace River and Saskatoon were 14.7 and 26.7 (Table 2). These differences occurred because the original paper reported values for single grid cells. However, the current analysis was based on averages across large regions that are composed of 1 12 grid cells. When single grid cells for Peace River and Saskatoon were examined in the current study, it was found that El values were indeed 24 and 30. Results, based on the CRU data for current climate, indi- cated that M. sanguinipes would have highest El values across Psyche 5 Figure 2: Predicted distribution and abundance (El) of Melanoplus sanguinipes for 2080 (CSIRO MARK 3.0) at six regions: (A) Lubbock, TX; (B) Lincoln, NE; (C) Gillette, WY; (D) Saskatoon, SK; (E) Peace River, AB; (F) Fairbanks, AK. Green = “Unfavourable” (El = 0-5); Tan = “Suitable” (El = 5-20); Orange = “Favourable” (El = 20-30); Red = “Very Favourable” (El > 30). most of the Great Plains of North America, extending from northern Texas to southern Saskatchewan (Figure 1). These results agreed with the distribution of M. sanguinipes as described by Riegert [20] and Pfadt [26]. Compared to these results, each of the three GCMs resulted in large differences for most model parameters, particularly El (Figures 2-4; Table 2). Across North America, the overall mean El values were 4.9 (CRU), 7.5 (CSIRO MARK 3.0), 7.9 (MIROC-H), and 7.3 (NCAR273 CCSM). Olfert and Weiss [17] grouped ecoclimatic indices into four categories: “Unfavourable” (El = 0-5), “Suitable” (El = 5-20), “Favourable” (El = 20-30), and “Very Favourable” (El > 30). Unfavourable described regions where M. sanguinipes would be very rare or may not occur; “Suitable” defined areas were grasshoppers would occur, usually in low densities; “Favourable” defined areas were densities could be high enough to result in crop loss; “Very Favourable” defined areas where grasshoppers regularly occur in high enough densities that result in crop loss. Based on this study, the extent of the area predicted to be “Very Favourable” were 11.2% (CRU), 16.2% (CSIRO MARK 3.0), 16.2% (MIROC-H), and 18.1% (NCAR273 CCSM) of North America. Species are more vulnerable to variations in temperature and precipitation when located near the outer limits of their geographic range than when located in the core area of the range. Sutherst et al. [19] defined a core area as a region with high El values and little or no stress. Populations near the outer limits of the core area spend a greater amount of time in climates that are marginally suitable (exposed to climatic stress), while populations near the core experience a greater amount of time in favourable conditions (minimal exposure to climatic stress). In this study, El values tended to increase in a northwestern direction and decrease for southern locations when the three GCMs were applied to the bioclimate model for M. sanguinipes. The percent of area (on a regional basis) with El > 20 varied across North America. For example, under current climate conditions (CRU), the model predicted that 0% of the Fairbanks region had El > 20 (Table 3). This value increased to as much as 57% of the area under conditions predicted by NCAR273 CCSM. As a result, the increase in the biological suitability of Fairbanks, AK, due to climate change was predicted to be similar to that of Lincoln, NE, under current climate conditions (CRU). In turn, the model predicted that the area surrounding Lincoln, NE, where El > 20 would decrease to 6.3% (NCAR273 CCSM), compared to 59.8% under current climate conditions (CRU). As indicated, there were regional differences across North America in output of the bioclimate model for M. sanguinipes when the three different GCMs were applied (Figures 2-4). The application of CSIRO MARK 3.0 climate data resulted in a northward shift of areas predicted to have 6 Psyche Figure 3: Predicted distribution and abundance (El) of Melanoplus sanguinipes for 2080 (MIROC-H) at six regions: (A) Lubbock, TX; (B) Lincoln, NE; (C) Gillette, WY; (D) Saskatoon, SK; (E) Peace River, AB; (F) Fairbanks, AK. Green = “Unfavourable” (El = 0-5); Tan = “Suitable” (El = 5-20); Orange = “Favourable” (El = 20-30); Red = “Very Favourable” (El > 30). reduced suitability for grasshopper populations within the southern Great Plains, relative to current climate conditions (CRU). There was a significant reduction in El values in states such as Colorado, Wyoming, and Missouri (Figure 2). In northwest Texas, the El values were predicted to decrease to less than 10. In more northern regions, however, El values were predicted to be higher in Alaska, northern Alberta, and Saskatchewan, relative to current climate conditions (CRU). Output based on the MIROC-H dataset resulted in a northwest shift of regions with El > 20 (Figure 3). Compared to current climate data (CRU), the MIROC- H GCM predicted that the overall area suitable for M. sanguinipes in the USA would be less than under current climate conditions. However, the suitable areas along the Rocky Mountains were observed to increase somewhat. The MIROC-H dataset predicted large El increases across most of the Canadian prairies, and extending northwest to include a continuous area northwest to Peace River, Alberta. Of the three GCMs, MIROC-H output resulted in the largest, continuous areas with El > 20. Unlike CSIRO MARK 3.0 and MIROC-H, NCAR273 CCSM predicted a reduction in El values for eastern North America. This GCM also predicted increased El values in the interior of British Columbia. In order to assess the potential impact of climate change in a more regional context, the resulting database was queried to analyze data at six regional locations between Lubbock, Texas, and Fairbanks, Alaska. Overall, the largest differences in El values were observed at northern and southern regions of North America. The shifts in El values were less in central locations. Compared to current climate (CRU), El values derived from GCMs resulted in increased El for the areas surrounding the three northern regions Saskatoon, Peace River, and Fairbanks (Figures 1-4, Table 2). The magnitude of the increase in El values, based on regional means, was 252%, 77%, and 33% greater for Fairbanks, Peace River, and Saskatoon, respectively, than those under current climate conditions. As a result, warming conditions were predicted to result in increased potential for M. sanguinipes outbreaks in these three regions. Outbreaks of M. sanguinipes have been recently reported in northern areas of North America. This species has been reported to be a sporadic, potentially damaging grasshopper pest of small grain crops in Alaska [27] and recent outbreaks of grasshoppers have been reported in the Peace River region of Alberta [28]. The three southern locations (Lincoln, Gillette, and Lubbock) had lower El values when GCMs were used as inputs into the model. Relative to the El values under current climate, the regional mean El values for Gillette, Lincoln, and Lubbock were predicted to be 23%, 29%, and 69% less, respectively. The regional responses to model input varied for the three GCMs (Table 3). The MIROC-H GCM resulted in the largest increase in El for the Peace River and Saskatoon regions, Psyche 7 Figure 4: Predicted distribution and abundance (El) of Melanoplus sanguinipes for 2080 (NCAR273 CCSM) at six regions: (A) Lubbock, TX; (B) Lincoln, NE; (C) Gillette, WY; (D) Saskatoon, SK; (E) Peace River, AB; (F) Fairbanks, AK. Green = “Unfavourable” (El = 0-5); Tan = “Suitable” (El = 5-20); Orange = “Favourable” (El = 20-30); Red = “Very Favourable” (El > 30). while the NCAR273 CCSM model resulted in the largest increase for the Fairbanks region. Of the three more southern regions, Lubbock exhibited the largest decrease in El values for MIROC-H. The weekly temperature index (TI) describes the weekly response of M. sanguinipes to the daily temperature cycles that occur during the growing season. Melanoplus san- guinipes overwinters in the egg stage. The timing and duration of spring hatch is influenced by the level of embryonic development going into winter, natural enemies, and soil temperature and moisture [29, 30]. In northerly regions, M. sanguinipes produces only one generation per year; in more southerly areas, a small proportion of the eggs oviposited do not enter diapause and may result in a lesser second generation. This species prefers warm, dry weather conditions. Warm temperatures early in spring favour nymphal development and in turn the timing of adulthood. Conversely, cool and wet conditions in spring results in increased nymphal mortality and delayed develop- ment. Crop loss due to feeding damage can occur throughout the growing season. Newly emerged seedlings in spring are most vulnerable, however, gradual plant defoliation may also contribute to decreased crop yield and quality [14, 16]. Later in the growing season, an extended, warm fall influences the longevity of adults, allowing them to continue reproducing until freeze-up [29, 30]. As a result, economic infestations are often associated with a prolonged period of consecutive seasons with above-normal temperatures [29]. Intermittent warm seasons tend to result in fluctuating populations [31, 32]. The GCM datasets, associated with temperatures that are warmer than CRU values, resulted in increased TI values for northern regions and reduced TI for southern regions. Olfert and Weiss [17] reported that incremental scenarios of +2°C and +4°C resulted in increased TI values and increases in both El and the potential area of Canada that would potentially be exposed to grasshopper outbreaks. At Fairbanks, TI values increased from 12.0 (CRU) to 20.1 (NCAR273 CCSM), resulting in more favourable tempera- tures during the growing season. Changes in central North America were less dramatic. Temperature indices in the Saskatoon region were predicted to increase from 30.7 (CRU) to 37.8 (NCAR273 CCSM). Excessively warm temperatures have been shown to hinder grasshopper populations [29, 33] . Output indicates that increased temperatures would result in higher heat stress (HS) values in northern Texas and Nebraska. The growth index (GI) is a weekly thermo hydrological index that describes conditions that are favourable for growth. CLIMEX outputs the number of weeks where the growth index is nonzero, effectively determining the length of the growing season. Growing season length and cold stress accumulation are two factors that limit the potential 8 Psyche Table 3: Baseline (CRU) and general circulation model (NCAR273 CCSM, MIROC-H, and CSIRO MARK 3.0) scenarios and percent of area with El values greater than, or equal to, 20 for Melanoplus sanguinipes at six locations in North America. Location GCM Scenario % of area with El > 20 Fairbanks, AK NCAR273 CCSM 57.1 CSIRO MARK 3.0 48.2 MIROC-H 49.1 CRU 0 Peace River, AB NCAR273 CCSM 75.6 CSIRO MARK 3.0 85.2 MIROC-H 94.1 CRU 19.3 Saskatoon, SK NCAR273 CCSM 100 CSIRO MARK 3.0 100 MIROC-H 100 CRU 92 Gillette, WY NCAR273 CCSM 100 CSIRO MARK 3.0 100 MIROC-H 88.1 CRU 100 Lincoln, NE NCAR273 CCSM 6.3 CSIRO MARK 3.0 25.9 MIROC-H 23.2 CRU 59.8 Lubbock, TX NCAR273 CCSM 40.7 CSIRO MARK 3.0 24.4 MIROC-H 12.6 CRU 98.5 for population growth in the Fairbanks region. Increased temperatures were predicted to not only decrease the rate of cold stress accumulation, but to also increase both the diapause index (DI) and the length of the growing season from 14 weeks to 17-18 weeks. The growing season in the Peace River region was predicted to increase from 1 9 weeks to 22 weeks and would result in a growing season that is similar to the current growing season in the Saskatoon region. Mills [34] predicted that regions north of 55 °N and west of 110°W have soils that are suitable for agricultural production and that climate change could positively impact small grain production in the area. This would suggest that M. sanguinipes populations could become established in these new agricultural areas in the event that they become accessible in the future. In southern regions, however, mean GI values and the number of weeks where GI values were positive decreased. Output indicated that prolonged periods of warm temperatures during the growing season could limit potential for grasshopper population growth. Extreme heat and drought tends to reduce crop growth while increase grasshopper feeding activity. Mukerji et al. [32] reported that increased competition for food can also result in population decline due to high mortality because of starvation. In conclusion, bioclimatic models have proven useful for studies investigating the potential impact of climate on insect populations. However, some cautions have been expressed regarding the utilization of this approach including: (i) biotic interactions may not remain the same over time (adaptation can, and is likely to, occur); (ii) genetic and phenotypic composition of populations may change over time and space; (iii) most species have some limitation to dispersal [35, 36]. In the instance of M. sanguinipes, the impact of biotic factors such as natural enemies (e.g., diseases, parasites) must also be considered. For example, termination of several grasshopper outbreaks in Canada were attributed to cool, wet weather and epizootics of Entomophthora grylli Fres. [20, 37]. Even though conditions may be predicted to be conducive to grasshopper populations under climate change, diseases could result in population decline. 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Pfadt, “Field Guide to Common Western Grasshop- pers,” Wyoming Agricultural Experiment Station Bulletin 912 (modified from 2nd Edition for electronic publication), 1994, http://www.sdvc.uwyo.edu/grasshopper/fieldgde.htm. [27] D. J. Fielding, “Developmental time of Melanoplus san- guinipes (Orthoptera: Acrididae) at high latitudes,” Environ- mental Entomology, vol. 33, no. 6, pp. 1513-1522, 2004. [28] O. Olfert, D. Giffen, and S. Hartley, “The 2009 Alberta, Saskatchewan and Manitoba grasshopper forecast,” in 2008 Crop Variety Highlights and Insect Pest Forecasts, Technical Bulletin No. 2009-01, Saskatoon Research Centre, Saskatoon, Canada, 2009. [29] R. Pickford, “Development, survival and reproduction of Camnula pellucida (Scudder) (Orthoptera: Acrididae) in relation to climatic conditions,” The Canadian Entomologist, vol. 98, pp. 158-169, 1966. [30] R. 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Hindawi Publishing Corporation Psyche Volume 2011, Article ID 105352, 12 pages doi:10.1 155/201 1/105352 Research Article Phase-Dependent Color Polyphenism in Field Populations of Red Locust Nymphs ( Nomadacris septemfasciata Serv.) in Madagascar Michel Lecoq, 1 Abdou Chamouine, 2 and My-Hanh Luong-Skovmand 1 1 Cirad Acridologie, 34398 Montpellier, France 2 Universite de Toliara, BP 185, Toliara 601, Madagascar Correspondence should be addressed to Michel Lecoq, lecoq@cirad.fr Received 26 May 2010; Accepted 12 August 2010 Academic Editor: Maria Marta Cigliano Copyright © 2011 Michel Lecoq et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Pigmentation of the Red locust hopper, Nomadacris septemfasciata Serv., was studied in natural conditions in Madagascar in relation to population density. More than one thousand hoppers were collected and described according to a semiquantitative method. A typology is proposed, strictly reflecting the increase in population densities. This correctly translated the progressive evolution of a solitary state into a gregarious state, while passing through several intermediate transiens stages. According to their density, hopper populations consist of a mixture, in various proportions, of several pigment types. The gregarization threshold is estimated at 100,000 hoppers/ha. A slight black spot on the hind femur is the first sign of gregarization. These results should improve the reliability of the information collected by the Malagasy National locust centre when surveying this major pest. They question the rapidity of the gregarization process in natural conditions as well as the stimuli involved. 1. Introduction Locusts are acridid species that exhibit density-dependant phase polyphenism and/or an ability to form marching hop- per bands and/or flying swarms resulting in outbreaks and plagues. Individuals are either of two extreme phenotypes: solitarious or gregarious [1, 2]. This polyphenism is contin- uous and all the intermediate stages, transiens, congregans or dissocians, are found between the two extreme phases, depending on the direction of the transformation. Induction of phase transformation can occur at any stage of develop- ment of the locust including the larva and the imago. It can be strengthened through generations and is reflected by a suite of changes in behaviour, morphometry, color, devel- opment, fecundity, and endocrine physiology (see recent reviews in [3-7]). Better understanding of locust phase polyphenism has an obvious applied potential and could lead, in the future, to nonconventional locust control mea- sures as a substitute for the chemical insecticides in use [5], but increasingly challenged because of their environmental impact [8, 9]. Currently, the precise characterization of the phases, and especially the intermediate transiens, is crucial for the effective implementation of preventive strategies against these locust pests, which require intervention as early as possible [ 10-13] . The transiens phase marks the first stages of the gregarization process. In the progressive development from remission periods to invasive periods, an understand- ing of the transiens phase can allow early detection and measurement of the degree of severity of the locust situation. In nature, behavioural changes are often the first char- acteristic observed as a result of a gathering of individu- als caused by external causes such as wind convergence, surface restrictions related to phenomena such as floods, and resource distribution [14-18]. This characteristic is difficult to precisely quantify for the intermediate transiens stages. Morphometry remains the best method to estimate the degree of phase transformation of an individual or a population. Morphometric charts can be used to monitor the gregarization process over generations [2, 3, 19]. In hoppers, only the color characteristics can be used. The coloring is one of the most obvious signs of the phase transformation in locusts [5]. Several studies have been carried out on the nature of the pigments involved, the underlying physiological mechanisms, and the influence of environmental conditions [2, 3, 20-23]. The color characteristics of the solitarious and gregarious phases have been shown numerous times (see, 2 Psyche e.g., Stower [24] for the Desert locust Schistocerca gregaria Forskal; Faure [25, 26] for the Red locust Nomadacris septemfasciata Serville 1838; Albrecht [20], Lecoq [27], Popov [28] for the Migratory locust Locusta migratoria L. 1758). The transiens phase remains, however, much less well documented, especially for the hoppers. Often, in the literature, the near infinite number of intermediate colors between the solitarious and the gregarious phases of these individuals is just mentioned. In the recent review by Pener and Simpson [5] the word transiens (or transient) appears 10 times only, when gregarious and solitarious are mentioned respectively, 560 and 440 times. Moreover, the phase transformation threshold is widely ignored. In nature, this threshold corresponds to the population density at which the interactions between individuals are large enough to allow the phase transformation process to start. It is sometimes given on the basis of an expert opinion without any results of specific observations [29]. The very validity of this concept is sometimes questioned because it also depends on the insect development stage and on the vegetation density [30]. This is crucial information from both an operational perspective to better manage locust preventive control and from a theoretical point of view to allow further detailed field studies on the phase transformation process determinism. The various difficulties in the characterization of tran- siens are particularly noted for the Red locust. In this species, despite various studies that have contributed to describing the pigmentation of the solitarious and of the gregarious stages [25, 26, 28, 31-33], the transiens remains poorly characterized and the phase transformation thresholds have never been established. More generally, phase polyphenism in the Red Locust is poorly understood and has rarely been proven experimentally and — in comparison to Desert and Migratory locusts — just a few papers are available for this species (see for instance [34-36]). The main effects of increased density on Nomadacris as revealed by laboratory work, were summarized by Uvarov a long time ago [2], and further research is obviously required [5]. In practice, the information collected by the locust services on the transiens phase is often unreliable [37] . We propose to clarify the color characteristics of the hopper individuals of this species in relation to population density. This study aims to provide a better understanding of the phase transformation thresholds and to improve the implementation of monitoring and pre- ventive control of this species. This work was carried out in the field in Madagascar where this locust is a major crop pest. 2. Materials and Methods 2.1. The Red Locust. The Red locust is well known through- out central and southern Africa [38, 39]. Some isolated populations can also be found in the lake Chad basin, the central delta of the Niger river in Mali, and the Cape Verde Islands [40]. The species undergoes phase transformation and its outbreak areas are mainly located in the Great Lakes region of East Africa, in Tanzania, Zambia, Malawi and Mozambique [41, 42]. Since the last great invasion of 1929-1944, which affected most African countries south of the equator, the species is controlled by an international organization, IRLCO (International Red Locust Control Organization) [43]. Infestations are now less frequent and are mainly focused in the reproduction areas, far from the cultivated areas [44], Large outbreaks occurred, however, between 1994 and 1996 [42, 43, 45, 46] and more recently in 2009 [47, 48]. In Madagascar, the Red locust is also a major pest and outbreaks are frequently observed with formation of hopper bands and swarms. No widespread invasion of the island has ever occurred as was frequently the case with the Migratory locust [49] whose last plague ravaged the Island between 1997 and 1999 [11]. The problem is now managed by the National Anti-Locust Centre as part of a crop protection strategy [40, 50, 51]. In Madagascar, the lifecycle of the Red locust has only been documented for the Betioky-Sud region, where this species produces just one generation per year [52-58], as in the rest of Africa. Mating and egg laying take place in November and December, at the onset of the rainy season, which lasts until April. Females generally lay eggs twice or three times, with a clutch of 20-100 eggs for gregarious locusts and 20-195 eggs for solitarious locusts. The eggs hatch after 24-36 days of incubation. The hoppers begin to appear in December. The hopper development passes by 6 instars for the gregarious individuals (1 to 6) and 7 instars for the solitarious (numbered 1, 2, 3, 4, 4a, 5, and 6 in order for the last instar to always carry the same number, the extra instar being before the reversal of the wing rudiments, between instar 4 and 5) [34]. The hopper development period lasts almost 2 months, ranging 50-70 days and the new generation of adults appears in April. They enter diapause to survive through the dry season (April- September), in refuge zones located away from breeding areas. Important seasonal migrations of solitary popula- tions take place between dry season refuge zones (where population densities are low) and rainy season breeding zones (where the populations concentrate and reproduce and where outbreaks are frequently observed) [59]. Samples of hoppers were collected from this latter area, where the first manifestations of gregariousness may occur (behavioral changes in the parental adults, and behavioral, pigmentary, morphological changes etc. in the offspring). 2.2. Sampling and Description of Hoppers. Red locust hop- pers were collected in south-western Madagascar in a vast area well-known as the breeding area of this species. The samples were taken during two successive rainy seasons from lanuary to March in 2007 and in 2008. During the two sampling periods, we continuously (each hour) recorded the air temperature and the relative humidity in one location in the sampling area (near Betioky-Sud). Both parameters were not very variable, during one sampling period as well as from one year to another (temperatures 2007/2008: min 22, 7°C ± 1,4/23, 1°C ± 1,5; max 35, 1°C ± 3, 1/37, 0°C ± 4,2; average 27, 8° C ± 1,7/28, 9° C ± 2,3; air humidity 2007/2008: min 39, 8% ± 14, 4/34, 4% ± 17, 7; max 82, 5% ± 7, 9/80, 2% ± 8, 4; average 64, 1% ± 10, 9/59, 1% ± 13, 3). The sampling sites were chosen based on the information provided by the National Anti-Locust Centre on the presence Psyche 3 of locust hoppers and their density. At each site, thirty hoppers were collected. The hopper density was evaluated by counting one hundred sample surfaces of one square meter each using a classical method commonly used by scouts from the locust centre [60, 61]. These hopper populations were derived from migrant adults arriving in the breeding area at the start of the rainy season and whose phase status was described broadly as solitarious as shown by survey data from the National Anti-Locust Centre (3741 observations conducted on the whole of south-western Madagascar in 2006 and 2007 on the parental populations). Some popula- tions in densities above the gregarious threshold, however, were observed (13 in all, including 4 light swarms at a density of between 160,000 and 200,000 imagos per hectare). For each hopper, the stage was determined by overall size, the size and the orientation of the wing pads, the number of eye stripes, and the color characteristics recorded using a standardized method. Only phase color (density) polyphenism and green/brown (humidity) polyphenism exist in the Red locust [5]. The latter is relatively limited as the hoppers of the single annual generation were still developing in relatively close conditions at the heart of the rainy season in lush vegetation. The proportion of green hoppers diminished late in the rainy season [57], In cages, homochromy has sometimes been observed in solitarious hoppers [26]. Regarding the phase color polyphenism, the descriptions in the literature concern essentially solitarious and gregarious individuals [25, 26, 28, 31-33]. For the transiens phase, information is scarce and mainly concerns the transiens dissocians [31, 33]. The characters finally selected were the background color (GC) and the degree of melanisation of the cephalic capsule (H), the degree of melanisation of the compound eyes (E) (with more or less visible stripes), background color of the pronotum (GP) and the degree of melanisation of its dorsal carina (CP) and lateral sides (LP), the degree of melanisation of the wing pads (W), and the presence and extent of a black spot on the distal part of the upper outer carina of the posterior femur (F). The latter criterion was supposed to be one of the first signs of gregariousness when the population density increases. The black abdominal maculation, difficult to quantify, was not considered. These eight criteria were recorded in the field using a semi-quantitative method (Figure 1). For E, H, CP, W, LP, and F, the extent of black pigmentation was coded 0 for absence of black pigmentation, 2 for a well-marked black spot and 1 for an intermediate situation. General pigmentation was recorded as green, brown, or orange for the cephalic capsule (GC), and as green, brown, or yellow for the pronotum (GP). Each hopper was individually identified and photographed under standard conditions for later checking of the rating criteria. 2.3. Data Analysis. The results were analyzed using the Addinsoft XLSTAT data analysis software (1995-2010). The data table [hoppers x color variables] containing the value of the different variables (semi quantitative) for each of the hoppers observed was converted into a disjunctive table (each nominal variable comprises several levels and each of these levels is coded as a binary variable). The latter was subjected to a Multiple Correspondence Analysis (MCA) to highlight the relationships between the various color vari- ables, on the one hand, and between the hoppers on the other hand, according to their similarity [62]. The hoppers and the variables were then classified according to their coordinates on the first factorial axes of the MCA using a hierarchical clustering method (Euclidean distance, Ward’s aggregation method). A typology of the hoppers, from the most solitar- ious to the most gregarious, was constructed on the basis of the results of this classification. Finally, each class of hoppers was related to the population density value in which they were most frequently observed. This helped establish the phase transformation threshold, that is to say, the population levels from which one hopper class moves to another, solitarious forms to more and more gregarious forms (or more exactly, from population consisting of a mixture of different color types in varying proportions to another). 3. Results 3.1. Hoppers Pigmentation. A total of 1139 hoppers were collected and their color characteristics were described, respectively, 36, 129, 123, 283, 233, and 343 hoppers of 1, 2, 3, 4 (including 4a), 5, and 6 instars. These hoppers were collected in 42 localities where hopper densities were (on a very regular density gradient) less than one hopper (solitarious populations) to several hundred hoppers per square meter (gregarious hopper band) (Figure 2). For densities greater than 150 hoppers/m 2 , no accurate count was possible and this class included densities ranging from 150 to several hundred hoppers per square meter. The hoppers collected from low-density populations (less than one hopper per square meter) were characteristic of the solitarious phase with a general green background coloring on all parts of the body (sometimes slightly yellowish) and a lack of black pigmentation (Figure 3). The pigmentation was generally very similar in all individuals with low variability. Rare individuals with a general brown background color were sometimes observed and were regarded as solitari- ous individuals within the traditional framework of the green/brown polyphenism (as is the case with the Migratory locust, e.g.,). Flowever, even if some of these individuals were found in low-density populations ( 100/m 2 ) (orange squares); LI to L6, hopper instars (green squares). -p CA Cl, 4 -* Lh 4 -» a 150/m 2 ) and could be regarded as representative of the gregarious populations. Types 4, 2, 5, and 7, which were very similar and predominated the medium-density populations, corresponded to solitaro-transiens populations. Finally, types 12, 3, 1, and 10, also similar, predominated the population at densities slightly greater (70-100/m 2 ) than for the previous types. These types could be grouped under the name transiens. These different types of hoppers can be distinguished easily and unambiguously on the basis of certain criteria for easy use in the field by the locust center scouts (Table 1). Thus, the appearance of the femoral spot signified the transition between solitarious and solitaro- transiens populations. Wing-pad melanisation distinguished solitaro-transiens and transiens hoppers. Finally, maximal melanisation of all body parts signified the onset of the gregarious type. Ultimately, the criteria used could easily assign each hopper to a particular phase category, either solitarious, solitaro-transiens, transiens, or gregarious. The hopper populations consisted of a mixture of hoppers that may belong to different color types. The percentages of each category developed progressively: a high proportion of solitarious individuals were found in lower density populations and higher densities had increasing proportions of solitaro-transiens, transiens and then gregar- ious individuals. Solitarious, solitaro-transiens, transiens or gregarious populations could thus be classified on the basis of the dominant color types within the population. 3.4. Pigmentation and Population Density. Some color vari- ables changed earlier than others to an increase in the hopper population density and could therefore be regarded as indicators of early signs of gregarization (Table 1). The eye stripes were still visible in half of the hoppers collected at a density of 30-70/m 2 . The eyes were dark for most of the hoppers at a density of 70-100/m 2 . Melanisation of the cephalic capsule, which started at 10-30/m 2 , was especially marked at a density of 70-100/m 2 . The background color of the cephalic capsule was green for most of the larvae at very low densities. The red-orange color became predominant only at a density of 30-70/m 2 . Melanisation of the dorsal carina of the pronotum appeared at a density of 10-30/m 2 and half of the hoppers were strongly marked at a density 8 Psyche Table 1: Color characteristics of the four hopper types. Characters Solitarious d < 10/m 2 Hopper types Solitaro-transiens d = 10-70/m 2 Transiens d = 70-100/m 2 Gregarious d > 100/m 2 E 0 0-1-2 1-2 2 H 0 0-1 0-1 2 GC green or brown green, green-orange, yellow or orange orange orange CP 0-1 1-2 2 2 LP 0 0 0-1-2 2 GP green or yellow green or yellow yellow yellow W 0 0 1 2 F 0 1 2 2 E: compound eye; H: cephalic capsule; GC: general pigmentation of the cephalic capsule; CP: median carina of pronotum; LP: lateral black spot of pronotum; GP: general pigmentation of the pronotum; W: wings rudiments; F: black spot on hind femur. of 30-70/m 2 . Conversely, the lateral pronotal spot was very pronounced in only one third of the hoppers at a density of 70-100/m 2 . It was strongly marked in all the hoppers for densities greater than 100/m 2 . The background color of the pronotum, mostly green in individuals in very low densities, turned yellow in the majority of hoppers at a density of 10- 30/m 2 . The darkening of the wing pad veins appeared later. It was significant in one third of individuals at a density of 70-100/m 2 . Above a density of 100/m 2 , all hoppers had strongly melanised wing pads. The femoral spot appeared at a density of 10-30/m 2 and it was predominant in half of the hoppers at a density of 30-70/m 2 . It was present and strongly marked in all hoppers at high densities (> 100/m 2 ). Finally, the first transiens hoppers appeared at a density of only 10- 20 hoppers/m 2 (Figure 5). 4. Discussion 4.1. Characterization of the Hopper Phase. The results from our field study on Red Locust hopper pigmentation estab- lished a clear typology, which strictly reflected the increasing densities of the populations. This correlates with the results obtained by Gunn and Flunter- Jones [63] on the regular gradient of pigmentation in relation to hopper density in the Migratory locust under laboratory conditions. In our case, this gradient reflected the gradual development of individuals from the solitarious state to the gregarious state through several intermediate transiens stages. Up to nine transiens categories were distinguished. Finally, only two were selected for a practical classification to highlight the first key stage of the gregarization process represented by the solitaro-transiens individuals. For each density, hopper pop- ulations were composed of a mixture of several color types in varying proportions. The proposed criteria were simple and unambiguous. The information collected by the National Anti-Locust Centre in Madagascar on the phase status of hopper populations could thus become precise, reinforcing the reliability of the survey protocol on this species. There was a possibility that environmental factors, other than population density, affected hopper coloration. For instance, temperature affects dark color patches in many acridids, especially in locusts [21]. In our case, temperature and humidity were not very variable during the sampling periods. The same results were obtained in 2007 and 2008 whatever the ecological conditions showing that population density was more important than any other factor — in our field conditions in Madagascar — to determine the coloration of hoppers of the Red Locust, contrary to an early statement by Lea and Webb in 1939 [64]. Our results confirmed (although only the pigmentation aspect was considered, which is just one component of phase polyphenism), that all hopper phases are present in Madagascar: the solitarious, all transiens-intermediate stages, and true gregarious hoppers were, in all respects, similar to those previously described in the literature, both in pigmentation and behavior (well-established and large, dense hopper bands of several hundred hoppers per square meter). These results therefore contradict the hypothesis by Roblot [65] and Roy [66], in force for almost half a century, according to which, as the environment is assumed to be less favorable to the Red locust in Madagascar as compared to Africa, only solitarious and transiens forms were able to exist on the island. This concept was so ingrained in the mentality, that the National Anti-Locust Centre in Madagascar deleted the term “gregarious” from the observation forms; only soli- tarious or transiens individuals were recorded. This is obvi- ously the best way to avoid observing gregarious individuals. Our results complemented recent studies (based on mor- phometric measurements) showing that the gregarious phase amongst the imagos was indeed present in Madagascar from the extreme south to the extreme north of the country [67]. A new gregarious area has moreover recently been identified following major outbreaks that occurred from 1999 to 2003 in the far north, surely as a result of intensive deforestation leading to the creation of new suitable biotopes [67, 68]. 4.2. The Gregarization Threshold in Red Locust Hoppers. Our results showed that the typology of hopper populations is strictly a reflection of hopper density. The color changes marking a first phase change were noted in the hoppers found in populations where the density is 10 hoppers Psyche 9 per square meter. The first real gregarious hoppers are found, occasionally, from 60-70 hoppers/m 2 and become predominant from 150/m 2 . Thus, the gregarization thresh- old can be estimated at about 100,000 hoppers per hectare. To our knowledge, this is the first indication of this type in the Red locust. For adults, this threshold has been recently estimated to be around 5,000 individuals per hectare by Franc et al. [67] . In comparison, the threshold is estimated at 2,000 adults/ha for the Migratory locust [69]. For the Desert locust, the threshold is estimated at 250-500 hoppers per hectare and varies between 5 and 0.5 hoppers/m 2 from the first to the fifth instar [29]. For the Red locust, the threshold is probably very likely to be modulated according to the hopper instar. The value quoted above was an average for all of our sampling (1th to 6th instars). Presumably it was lower in the 6th instar and higher in the first, which should be verified on a larger sample. The gregarization threshold maybe reflective of the hop- per environment, particularly the structure of the vegetation. The latter may be more or less heterogeneous and may promote local concentrations of populations. In general, the distribution of resources such as food, favorable areas of microclimate, and roosting sites are all factors that may help promote gregariousness as has been shown especially in the Desert locust [16-18]. However, the Saharan habitats of the Desert locust, a plurivoltin species, can be very diverse, both in space and time. On the contrary, the hoppers of the only annual generation of the Red locust in Madagascar varies between January and March, within the breeding area in the south-west, in a lush, dense vegetation (100% coverage, plant height between 40 and 80 cm on average) whose structure is very similar from one year to the other. We believe that the threshold concept takes on certain significance and is of considerable value for the local antilocust survey service, even if the figures are only a rough estimate. Finally, it is interesting to compare our threshold values to those recorded experimentally for the density at which the coordinated marching behaviour of the gregarious popula- tions appears. Collett et al. [18] has shown experimentally, in the third hopper instar of the Desert locust, coordi- nated movements that are well marked at densities above 74 hoppers/m 2 . However, at densities below 18 hoppers/m 2 , no coordinated movement is noted. Even if the species and conditions were very different from ours (hoppers in the field in dense vegetation compared to hoppers in a circular arena without vegetation), it is interesting to note that our observations give similar values with a phase transformation threshold estimated at 10 hoppers/m 2 and the emergence of real gregarious hoppers from densities of 60-70 hoppers/m 2 . This could be the result of an identical “radius of influence”, whatever the circumstances and regardless of the stimuli involved. Differences in the gregarization threshold for Migratory, Red and Desert locusts could therefore be the result of the respective structures of these three species’ habitats. For adults, the lowest gregarization thresholds were indeed noted for the Desert locust living in habitats where vegetation is scarce and often in clumps and highest for the Red locust living in environments with much wetter, tall, and dense vegetation. 4.3. Phase Transformation Rapidity and Parental Antecedents. The fact that from solitarious parental populations we can obtain hoppers with perfectly gregarious color characteristics in the next generation may question the rapidity of the gregarization process in the Red locust. Can we consider a parental effect on our results? We know that phase char- acteristics are transmitted to offspring, a phenomenon well known in the Desert locust and the Migratory locust [70- 74]. In Madagascar, the early stages of phase transformation are often initiated at the beginning of the rainy season when solitarious populations migrate from the dry season refuge areas to the rainy season breeding areas. Such a phenomenon is observed in the Migratory locust [49, 60] as well as in the Red locust [59]. These migrations often lead to sudden and rapid increases in adult densities allowing the appearance of the first behavioral manifestations of gregarization. The den- sity shock suffered by females during laying can be inherited and affect the phase of the descendant and, in particular, the expression of color polyphenism in the hoppers. Such a parental effect could explain the rapidity of the process observed in the hoppers. Even if the parent populations appear to have been mostly solitarious, obser- vations conducted by the National Anti-Locust Centre have shown the presence of some population densities above the gregarization threshold and a few swarms. In early 2006, in the dry season, the average density in south-western Madagascar was 94 adults/ha (max 680). In the early rainy season of 2006-2007, the average density increased to 664/ha (with one swarm at 160,000/ha), then decreased to 272/ha in the early dry season of 2007 (with four swarms and nine cases where the density exceeded the gregarization threshold of 5,000 adults per hectare). All transiens or gregarious hoppers could descend from parent populations that have already experienced, to varying degrees, a density shock in their history when laying or early in their development over a number of generations. This is impossible to determine, but it would explain the wide range of phase conditions registered in our database. 4.4. Relative Importance of Various Stimuli in the Gre- garization Process. The low densities from which the first transformation phase signs were noted in the Red locust raise questions about the nature of the stimuli involved. Progress has been made in recent years towards understanding the stimuli associated with crowding that evoke gregarious - phase characteristics in S. gregaria. The main focus has been on induction of gregarious behavior [5]. Simpson et al. [16, 17, 72, 75-78] have brilliantly shown in the Desert locust that mechanical stimuli appear to intervene initially; they are potent inducers of phase-transformation behavior and have a central role. The mechanoreceptors responsible are located on the outer face of the hind femur. Various authors have shown, however, especially in the Desert locust, that visual and olfactory stimuli (less active or completely inactive separately) can act synergistically and lead to both gregarious behavior and the development of black spots and yellowing of the cuticle, characteristic of gregarious hoppers [79-81]. A former experiment by Launoisetal. [82], 10 Psyche on the Migratory locust suggests that the daily rhythm of solitarious adults activity collected in the field and tested using actography near the field, can be changed depending on the density of individuals in the experimental room without any tactile contact between them, suggesting the influence of olfactory or visual stimuli in the early stages of behavioral gregarization. More recently, Simpson’s group has also shown that tactile stimulation (of the antennae in this case) is necessary to induce behavioural gregarization in the Australian plague locust, Chortoicetes terminifera (Walker, 1870) [83]. Thus convergent behavioral responses to crowding have certainly evolved, employing different sites of sensory input according to the species. In our case, no apparent manifestation of behavioral gregarization (coordinated movements) seems apparent in hopper populations of the Red locust at densities equal to the gregarization threshold or 10-20 hoppers/m 2 only, far from the hundreds of individuals in gregarious or pregre- garious hopper bands. During the rainy season, the hoppers developed in homogeneous, dense vegetation covering the entire ground at an average height of 40 to 80 cm between January and March. However, the first signs of gregarization occurred at these densities, at least the pigmentary signs. The probability of tactile contact in these conditions seems relatively low. Visual, olfactory or auditory signs could also be very important in the early stages of the gregarization process when locust densities are too low (and therefore when a natural tendency for repulsion still occurs) and vegetation density is too high to allow frequent contact between individuals. Of course, in nature, mechanical, chemical, visual and auditory stimuli are all present and must act synergistically. The importance of these various factors in the induction of gregarization in the Red locust needs to be clarified in natural conditions. An excellent knowledge of the transiens phase and of its first signs is thus of fundamental interest. Acknowledgments Financial support was provided by the African Bank for the development, within the framework of the project for preventive locust control in Madagascar (2005 to 2009) and with a contract with the Malagasy National centre for rural development (FOFIFA). The authors are grateful to these organizations for their confidence. They also make a particular point in thanking the Malagasy National locust centre, its survey department, and all the field staff having greatly contributed to facilitate the sampling work, as well as Professor Anne -Marie Razanaohaitse, from the University of Tulear, for her continuous support and encouragements. References [ 1 ] G. B. Uvarov, “A revision of the genus Locusta, L. ( =Pachytylus , Fieb.), with a new theory as to periodicity and migrations of locusts,” Bulletin of Entomological Research , vol. 12, pp. 135— 163, 1921. [2] G. B. Uvarov, Grasshoppers and Locusts , Cambridge University Press, Cambridge, UK, 1966. [3] M. P. Pener, “Locust phase polymorphism and its endocrine relations,” Advances in Insect Physiology , vol. 23, pp. 1-79, 1991. [4] M. P. Pener and Y. Yerushalmi, “The physiology of locust phase polymorphism: an update,” Journal of Insect Physiology , vol. 44, no. 5-6, pp. 365-377, 1998. [5] M. P. Pener and S. J. 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Lecoq, “Etude experimentale de Factivite locomotrice du Criquet migrateur malgache dans la nature,” Annales de la Societe Entomologique de France, vol. 12, pp. 433-451, 1976. [83] D. A. Cullen, G. A. Sword, T. Dodgson, and S. J. Simpson, “Behavioural phase change in the Australian plague locust, Chortoicetes terminifera, is triggered by tactile stimulation of the antennae,” Journal of Insect Physiology, vol. 56, no. 8, pp. 937-942, 2010. Hindawi Publishing Corporation Psyche Volume 2011, Article ID 741769, 16 pages doi:10.1 155/201 1/741769 Review Article Density-Dependent Phase Polyphenism in Nonmodel Locusts: A Minireview Hojun Song Department of Biology, University of Central Florida, 4000 Central Florida Boulevard, Orlando, FL 32816-2368, USA Correspondence should be addressed to Hojun Song, song@mail.ucf.edu Received 1 June 2010; Accepted 19 September 2010 Academic Editor: Gregory A. Sword Copyright © 201 1 Hojun Song. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Although the specific mechanisms of locust phase transformation are wellunderstood for model locust species such as the desert locust Schistocerca gregaria and the migratory locust Locusta migratoria, the expressions of density-dependent phase polyphenism in other nonmodel locust species are not wellknown. The present paper is an attempt to review and synthesize what we know about these nonmodel locusts. Based on all available data, I find that locust phase polyphenism is expressed in many different ways in different locust species and identify a pattern that locust species often belong to large taxonomic groups which contain mostly nonswarming grasshopper species. Although locust phase polyphenism has evolved multiple times within Acrididae, I argue that its evolution should be studied from a phylogenetic perspective because I find similar density-dependent phenotypic plasticity among closely related species. Finally, I emphasize the importance of comparative analyses in understanding the evolution of locust phase and propose a phylogeny-based research framework. 1. Introduction The contemporary definition of locusts is fairly strict and narrow. Pener [ 1 ] defined locusts as grasshoppers that belong to Acrididae (Orthoptera: Caelifera) that meet two criteria: (1) they form at some periods dense groups comprising huge numbers, bands of hoppers, and/or swarms of winged adults which migrate; (2) they are polyphenic in the sense that individuals living separately differ in many characteristics from those living in groups. There are a number of grasshop- per species that satisfy the first criterion and thus often loosely called locusts [2-5]. However, the second criterion, the expression of density- dependent phase polyphenism, is rarer [6] and has only been convincingly documented in the migratory locust, Locusta migratoria, the brown locust, Locustana pardalina, the desert locust Schistocerca gregaria, the Central American locust, S. piceifrons, the South American locust, S. cancellata, and the red locust, Nomadacris septemfasciata, and to the lesser degree in the Moroccan locust, Dociostaurus maroccanus. In these species, color, behavior, morphology, biochemistry, and life history traits are strikingly affected by the change in local population density [2]. Those species that cause tremendous agricultural damage but do not express visible phase polyphenism are often referred to as locusts, but whether they strictly fit the definition of “locusts” remains rather ambiguous. Uvarov [5, pages 142-150] dedicated a chapter titled “Antecedents of gregarious behaviour” to discuss these borderline species. Pener and Simpson [2] also listed 23 acridid species that show elements of density- dependent polyphenism and briefly mentioned phase-like expressions in those species not typically categorized as “true locusts.” It is difficult to prove whether a given grasshopper species displays density-dependent phase polyphenism. It is because the presence of density- dependent phase polyphenism is something that has to be tested through explicit experiments [7], especially when its expression is not readily visible. A species in question has to be reared in both isolated and crowded conditions in a carefully controlled manner, and the resulting phenotypes have to be quantified and statistically compared [8]. Also, the expressions of density-dependent polyphenism may be subtle and not manifest in an extreme way found in model locust species such as S. gregaria and L. migratoria. A good example of this can be illustrated in the Australian plague locust, Chortoicetes terminifera, which is convincingly demonstrated to display a strong form 2 Psyche of density-dependent behavioral polyphenism without the change in color [9]. Just because extreme manifestation of many phase-related characters occurs in model locust species, we cannot expect other locust species to express the same traits. After all, these locust species are the product of their own evolutionary history and finely adapted to their local environments [10]. If we accept the fact that locust phase polyphenism evolved multiple times [4], we also have to accept the fact that there are many ways to become locusts. It is important to realize that many traits associated with locust phase polyphenism do not necessarily evolve as a whole [4, 11]. Locust phase polyphenism is an ultimate expression of many different phenotypically plastic responses that are affected by the change of local population density. Song and Wenzel [11] showed that the evolution of density-dependent color plasticity precedes the evolution of behavioral plasticity in Cyrtacanthacridinae and that the physiological mechanisms necessary to produce density- dependent color morphs are phylogenetically conserved in the subfamily. Thus, understanding the phylogeny is exceedingly important in understanding the evolution of locust phase polyphenism. Tremendous advances have been made in understanding the mechanism of phase transformation in 5. gregaria and L. migratoria [2], but not much is known about the density- dependent phase polyphenism of nonmodel locust species. The present paper is an attempt to review all available literatures regarding the effect of population density in nonmodel locust species. I do not dwell on S. gregaria and L. migratoria because these model species have been the subject of several recent reviews [2, 12-14], but I only mention them when comparison and contrast with nonmodel species become relevant. When discussing each species, I try to incorporate available taxonomic and phylogenetic informa- tion [15]. Finally, I propose a robust research framework that incorporates a phylogenetic approach in studying the evolution of density-dependent phase polyphenism. 2. Expression of Density-Dependent Phase Polyphenism of Nonmodel Locusts In this section, I review taxonomy, phylogeny, and the existence and expression of density-dependent polyphenism in nonmodel locust species across Acrididae. There is an enormous body of literature dedicated to biology, ecology, population dynamics, and pest management of these species, much of which is reviewed in Uvarov [5, 16], COPR [17], and others. I do not attempt to review these topics again unless they are relevant for discussion. Data presented in the following sections are summarized in Tables 1 and 2. 2.1. Locust Species in Schistocerca. The genus Schistocerca Stal, 1873 contains about fifty species and is widely dis- tributed in the New World. It is difficult to pinpoint the exact number of species in the genus because the most comprehensive revision of the genus by Dirsh [18] made numerous synonymies based on an obscure morphometric species concept, which are now considered to be incorrect. Harvey [19] revised the Americana complex based on a series of hybridization experiments, and Song [20] revised the Alutacea group based on morphological characters. A large complex of species which is currently synonymized under S. nitens needs to be examined thoroughly. Schistocerca is also well known for its transatlantic disjunction distribution in which the desert locust S. gregaria is the only Old World representative of the genus. A considerable amount of controversies and debates have centered on the origin of the desert locust [21, 22]. Schistocerca occupies a rather unique position in the study of locusts because it contains multiple locust species. The desert locust S. gregaria is of course the most well known of all locusts in terms of both swarm dynamics and the mechanism of phase transformation [2], The Central American locust S. piceifrons and the South American locust S. canccllata are important swarming locust species in the New World, and the Peru locust S. interrita has recently been recognized as a locust. There have been reports of the American grasshopper S. americana, which is closely related to other swarming species in the genus, being able to form hopper bands and adult swarms [62], but no conclusive evidence exists to show that it is a locust [63] . It is important to realize that the swarming species in Schistocerca do not form a monophyletic group. Based on hybridization studies and phylogenetic studies, it is recognized that swarming S. piceifrons is sister to nonswarming 5. americana [19, 22, 64], and swarming S. cancellata is sister to nonswarming S. pallens [19, 21, 22, 26]. In other words, locust phase polyphenism appears to have evolved multiple times even within the same genus. Many nonswarming sedentary Schistocerca species are capable of expressing density-dependent color polyphenism [65-69], suggesting that color plasticity is a phylogenetically conserved trait in the genus [11]. Interestingly, an isolated population of S. gregaria in South Africa is not prone to gregarization and is often referred to as the subspecies S. gregaria flaviventris [27]. Schimdt and Albiitz [70] also found that a population of S. gregaria from Canary Island expressed much reduced phase traits even after intense crowding. Similarly, a Chilean population of S. cancellata is also not prone to gregarization [27]. These examples suggest that density- dependent behavioral plasticity is not a fixed trait for these locust species, and it may be reduced or lost due to adaptation to local environments or drift [71]. Schistocerca piceifrons (Walker, 1870) is distributed throughout Central America and the northern part of South America [19, 23, 24]. Two subspecies are recognized, the nominal subspecies and S. piceifrons peruviana which occurs in high elevations of Peru and Ecuador [24, 29, 72]. Recently, a migrant population was found on Socorro Island (Mexico) in the Pacific Ocean [73, 74]. In Mexico, where the locust is commonly referred to as langosta voladora, there are two generations, spring and fall, and the fall generation adults go through a reproductive diapause during the winter dry season [23]. Schistocerca piceifrons is found where there is between 100 and 250 cm of annual rainfall, distinct dry winter season, and no cold season. It prefers semixerophytic mosaic vegetation and feeds on a wide variety of herbaceous plants. It is a typical swarming Psyche 3 Table 1: Expressions of density-dependent phenotypic plasticity of the species included in this paper. When there is conclusive evidence on presence or absence of density- dependent phenotypic plasticity, it is noted as such. Asterisk denotes the possibility based on inconclusive and anecdotal evidence. Unknown denotes the lack of quantitative data. Density-dependent phenotypic plasticity Species Nymphal color Morphometries ratios Physiology Behavior References Cyrtacanthacridinae Schistocerca gregaria present present present present [2, 16] Schistocerca piceifrons present present present present* [23-25] Schistocerca cancellata present present present present* [19, 26-28] Schistocerca interrita present* present* unknown unknown [29-32] Nomadacris septemfasciata present present present present* [16, 33-35] Patanga succincta present present present unknown [17, 36, 37] Austracris guttulosa absent absent absent unknown [17, 36-40] Anacridium melanorhodon present absent absent unknown [41,42] Oedipodinae Locusta migratoria present present present present [2, 16] Locustana pardalina present present present present* [5, 16, 33,43] Oedaleus senegalensis present* unknown unknown unknown [41] Gastrimargus musicus present present unknown present* [44] Pyrgodera armata present* unknown unknown unknown [45] Chortoicetes terminifera absent present present present [9, 46] Austroicetes cruciata absent present unknown unknown [46] Aiolopus simulatrix present* unknown present* unknown [41,47] Ceracris kiangsu unknown unknown unknown unknown [17] Calliptaminae Calliptamus italicus absent present present present* [48-51] Gomphocerinae Dociostaurus marrocanus present present present present* [5, 16, 52, 53] Rhammatocerus schistocercoides present* present* unknown unknown [54, 55] Gomphocerus sibricus absent absent unknown unknown [5, 56] Melanoplinae Melanoplus sanguinipes present absent unknown unknown [5, 56-58] Melanoplus differential is unknown absent unknown unknown [59, 60] Proctolabinae Coscineuta virens absent absent unknown unknown [61] locust with distinct density- dependent phase polyphenism in color, morphology, and other life history traits [24, 25]. In terms of color, nymphs are green at low density, but at high density they develop extensive black pattern in head, pronotum, wingpads, abdomen, and legs with pink or peach- red background [24, 25]. Schistocerca cancellata (Serville, 1838) is distributed in the southern half of South America, including Argentina, Bolivia, Paraguay, Uruguay, Chile, and southern Brazil [17]. It used to be known as S. paranensis, which previously referred to the locust in the New World, but hybridization experiments confirmed that there were two locust species in the New World, the Central American locust S. piceifrons and the South American locust S. cancellata [19, 26, 64]. It is adapted to temperate and subtropical climate, and there is an annual cycle of migration and breeding within the invasion area that is strongly influenced by weather and its seasonal variations [19, 27]. There are several permanent zones of breeding, which consist of an area of desert or semidesert within an annual rainfall of over 500 mm [17]. The species matures and oviposits in areas where there has been rain. The species used to be a major plague species in the first half of the 20th century [75], but in recent years, large-scale infestations have become infrequent [27], and outbreaks are limited to the semiarid areas in north-west Argentina [76], possibly due to very effective control measures. The South American locust is a classic swarming species with pronounced density-dependent phase polyphenism similar to the congeneric S. gregaria [19, 28]. Schistocerca interrita Scudder, 1899, has been known as a nonswarming grasshopper occurring in Peru for a long time [77]. During 1983 and 1984 after the “El Nino” phenomenon, a severe outbreak of S. interrita reaching a proportion of a plague was reported in the northern coast of Peru [30]. It has been hypothesized that when there is abundant rainfall due to unusual events such as El Nino, 4 Psyche Table 2: Expressions of swarm dynamics and ecological characteristics of the species included in this paper. When there is conclusive evidence on presence or absence of a given phenomenon, it is noted as such. Asterisk denotes the possibility based on inconclusive and anecdotal evidence. Unknown denotes the lack of quantitative data. Swarm dy namics Ecological characters Species Hopper band Adult swarm Group mating Group oviposition Habitat preference Food preference Cyrtacanthacridinae Schistocerca gregaria present present present present arid and semiarid land herbivorous Schistocerca piceifrons present present present present semixerophytic mosaic vegetation desert or semidesert with herbivorous Schistocerca cancellata present present present present annual rainfall of over 500 mm herbivorous Schistocerca interrita present present present present dry wooded area herbivorous Nomadacris septemfasciata present present absent absent treeless grassland with seasonal flood graminivorous Patanga succincta absent present absent absent grassland graminivorous Austracris guttulosa absent present absent absent grassland graminivorous Anacridium melanorhodon present present absent absent dry open woodland near Acacia arborivorous Oedipodinae Locusta migratoria present present present present variable graminivorous Locustana pardalina present present present present arid land graminivorous Oedaleus senegalensis present present unknown unknown drier savannah costal and subcostal regions graminivorous Gastrimargus musicus present present present present of Australia where annual rainfall is greater than 500 mm alluvial plains and graminivorous Pyrgodera armata present absent unknown unknown adjoining hills with clay or stony soils herbivorous Chortoicetes terminifera present present present present semiarid land drier and more open graminivorous Austroicetes cruciata present present present present grasslands and semideserts with 200-500 mm annual graminivorous rainfall Aiolopus simulatrix present present present* present* grassland graminivorous Ceracris kiangsu present absent unknown unknown bamboo forest monophagous on bamboo Calliptaminae Calliptamus italicus Gomphocerinae present present present present dry steppe zones herbivorous Dociostaurus marrocanus present present present present semiarid steppe or semiarid desert graminivorous Rhammatocerus schistocercoides present present present present shrub-like and wooded savannas graminivorous Gomphocerus sibricus Melanoplinae present present unknown unknown forest margins graminivorous Melanoplus sanguinipes present* present unknown unknown grasslands and meadows graminivorous/ forbivorous Melanoplus differentialis present present unknown unknown tall herbaceous vegetation growing in wet meadows graminivorous/ forbivorous Proctolabinae Coscineuta virens present present present present forest herbivorous/ forbivorous Psyche 5 Lambayeque desert becomes a suitable breeding ground for S. interrita , which eventually leads to an exponential population growth [30, 31]. An anecdotal report of a locust swarm in Lambayeque is known from 1578, which can be probably attributed to S. interrita [31], but the most recent upsurge occurred in 1997-2003 in Lambayeque and Cajamarca of northern Peru. Schistocerca interrita is adapted to dry wooded area at the elevation of 3500 m above sea level, and population dynamics and basic ecology have not been thoroughly studied (see [29, 31]). At low density, nymphs are green, but they develop black pattern with yellow background at high density. Unlike the gregarious nymphs of 5. piceifrons which develop broad black patterns in the lateral face of the pronotum, the gregarious nymphs of S. interrita develop black patterns with clearly defined margins, so that the lateral face of pronotum has a distinct yellow triangle [32] . Both hopper bands and adult swarms are known in this species and sexually mature adults turn yellow. 2.2. Locust Species in the Nomadacris-Patanga-Austracris- Valanga Complex. Within Cyrtacanthacridinae, Nomadacris Uvarov, 1923, Patanga Uvarov, 1 923, Austracris Uvarov, 1923, and Valanga Uvarov, 1923 form a monophyletic group based on morphological characters including male genitalia, male subgenital plate, and male cerci [11]. The taxonomic history of this group is unnecessarily confusing, which I discuss in detail because I think it is relevant in discussion of the evolution of locust phase polyphenism in this group. Uvarov [78] first described the genus Patanga based on the shape of hind femora, prosternal process, and male subgenital plate. The other three genera were described later in the same publication. Dirsh [79] first suggested that the type species, Gryllus ( Locusta ) succinctus Johansson, 1763, Uvarov [78] used to describe as Patanga did not correspond to its original description by Johansson. He noted that there was an available name ( Acridium assectator Fischer von Waldheim, 1833) matching Uvarov’s [78], and Linneaus’ original description matched that of Acridium nigricorne Burmeister, 1838, which was a type species of yet another genus Valanga. Uvarov [80] soon published a rebuttal, and Melville [81] carefully summarized this affair. The final opinion from ICZN was published in 1973 in favor of keeping nomenclatural stability [82]. Nevertheless, Dirsh [83] published a revision of Cyrtacanthacris and synonymized Nomadacris, Valanga, Patanga, and Austracris under Cyrtacanthacris on the ground of morphological sim- ilarities. Jago [84] criticized Dirsh’s action and reinstated the ranking of genera synonymized by Dirsh [83]. In doing so, he suggested that Nomadacris, Patanga, and Austracris were congeneric and lowered the taxonomic ranking to subgenera under Patanga, which had a priority. He also argued that the genus Valanga should be maintained in line with the opinion of the ICZN [82]. Thus, Jago’s [84] action resulted in three genera: Cyrtacanthacris, Valanga, and Patanga. Nomadacris septemfasciata was, however, one of the most important locust species, and there were numerous agricultural reports using that name. In order to promote taxonomic stability, Key and Jago [85] proposed to make Nomadacris have a priority over Patanga, on the ground of Jago [84] being the first reviser. Thus, Patanga and Austracris were considered subgenera of Nomadacris. Later, Key and Rentz [86] asserted that the Australian representatives were morphologically distinct and removed Austracris from synonymy. All this taxonomic confusion is due to the fact that these four genera are very closely related. Because of the conventional usage of the names, I use the generic name sensu Uvarov [78], but it is certainly possible to consider these four genera congeneric. This leads to a very interesting point in terms of the evolution of locust phase polyphenism. Just like Schistocerca, which has a few swarming locust species, but mostly sedentary species, this generic complex also has the mixture of swarming and nonswarming species. Just like S. gregaria which is the only African representative of the genus, which happens to express the most extreme form of locust phase polyphenism of all Schistocerca locusts, N. septemfasciata is the only African representative of the generic complex, which also happens to express the most extreme form of locust phase polyphenism in the complex. This is a fantastic case of parallel evolution. Locust species in Schistocerca and this generic complex are very similar in terms of their color pattern and the same is true among the sedentary species in these two groups. However, the exact expressions of locust phase polyphenism are distinctly different between the two. The red locust, Nomadacris septemfasciata (Serville, 1838), is distributed in most of Africa, south of Sahara, and in Madagascar [17]. Seasonal and annual variation of flood gives rise to unstable mosaic of very tall grasses and sedges and short grasses where N. septemfasciata thrives. Several studies were carried out in the Rukwa Valley, Tanganyika (Tanzania), one of three known outbreak areas of the red locust [87-91]. Several studies have emphasized the impor- tance of physical structure of vegetation in concentration of individuals [88-90], and both nymphs and adults are known to roost on stems of Echinochloa pyramidalis, the dominant tall grass and Cyperus longus, the dominant short grass species [90] . The red locust is a classic swarming locust that expresses an extreme form of density- dependent phase polyphenism [5,33]. Isolated nymphs are green, but crowded nymphs develop extensive black pattern with orange frons and yellow background [41]. Adult morphometries, number of instars, and the rate of sexual maturation are all affected by the change in population density [5, 34, 35]. Both hopper bands and adult swarms are welldocumented [90, 92] , but group mating and group oviposition have not been documented from this species. Adults go through a very long reproductive diapause up to 8 months [17, 87], and the particular stage of sexual maturation can be determined by examining the color of hind wing, which changes from transparent to pink to purple red [92]. The Bombay locust, Patanga succincta (Johannson, 1763) is widely distributed in southwestern Asia (India, Philip- pines, Indonesia, Malaysia, Thailand, Japan, and China) [ 1 7, 93] . No major swarm has been reported since 1908 although small populations seem to be consistently found [94]. Adults of P. succincta form a typical swarm, but it is not clear from the literature whether this species also exhibits hopper bands. Douthwaite [95] observed nymphal behavior in Thailand. 6 Psyche Nymphs favored grass species such as Imperata and maize, which co-occurred with low vegetation such as Brachiaria. He observed that nymphs move vertically on maize where they mostly fed. The vertical movement was rapid, but it was not synchronized among other individuals in the population. Feeding occurred during warm weather and nymphs climbed up the maize and descended to Brachiaria which they used as a shelter. Even when the population density is high, the hoppers move little [17]. Isolated nymphs are green, and crowded nymphs develop black mottles with yellowish orange or fawn background, but not extensive black patterns observed in other locust species [36, 37]. Morphometric ratios in adults do seem to be affected [36]. Both group mating and group oviposition are not reported from this species. The spur-throated locust, Austracris guttulosa (Walker, 1870), is distributed throughout Australia and adjacent regions [96]. It is a tropical, ambivorous species, adapted to monsoon climate with a long dry season [97]. Although it feeds on a wide variety of plants, grass is preferred. Immature adults form a migrating swarm. The size of a typical swarm can be very large and dense, and it can travel up to 400-500 km in a week [38]. Although adults exhibit impressive migratory swarms, A. guttulosa does not exhibit many traits that are commonly associated with locust phase polyphenism [38]. For example, nymphal color does not become conspicuous upon crowding although density- dependent green/brown polymorphism appears to occur [39], adult morphometric ratios remain constant upon crowding [40], nymphs have never been observed moving in dense bands despite high local densities [38], and oviposition never occurs collectively in egg beds, suggesting the lack of group oviposition [38]. 2.3. Anacridium melanorhodon. The genus Anacridium Uvarov, 1923, contains 13 valid species widely distributed in Africa and southern Europe [98]. The identity of A. javanicum which was described from a single female speci- men from Java is questionable, and it might be a specimen belonging to Valanga which might have been mistaken as Anacridium. The Sahelian tree locust, A. melanorhodon (Walker, 1870), is distributed in the Sahelian zone in Africa. Two subspecies are known, the nominal subspecies occurring in the west and A. melanorhodon arabafrum occurring in the east through Arabia to Iran [17]. It is an arboricolous species, intimately associated with various Acacia species. In the field, especially in winter, swarms occasionally occur. A typical swarm of A. melanorhodon is small, less than one square kilometer, but a swarm as large as 20 km in length has been observed [42]. One of the characteristics of A. melanorhodon is its nocturnal habit. Most feeding and flight activities occur at night, and the species is locally known as sari-el-lel, which means the night wanderer. Both adults and nymphs roost on Acacia trees or other available tall trees. This roosting behavior seems to lead to the concentration of population, which in turn leads to the development of swarms. No characteristic group oviposition as in 5. gregaria was observed, but the egg pod density can be high due to the structure of vegetation [42]. Hatchlings from such high- density places gradually concentrate into groups and bands. Cohesive and directional marching behavior has been observed, but the density of hopper bands can be as low as one individual per square meter. Crowded nymphs develop black mottles with yellow background while isolated nymphs are green [41]. Adult morphometric ratios are not affected by population density [42]. The congeneric A. wernerellum is known to behave like a locust in rare circumstances [42], and its response to density is probably similar to A. melanorhodon. 2.4. Locust Species in the Oedipodine Tribe Locustini. The oedipodine tribe Locustini is of particular interest because it contains several species prone to density-dependent phe- notypic plasticity including the migratory locust, Locusta migratoria, the brown locust, Locustana pardalina, the Sene- galese grasshopper, Oedaleus senegalensis , the yellow- winged locust, Gastimargus musicus, and the Iranian grasshopper, Pyrgodera armata. Although there is no phylogenetic work focusing on this tribe as a whole, a recent molecular phylogenetic study by Fries et al. [99] included three genera of this tribe, Locusta, Gastrimargus, and Oedaleus and found that these form a strong monophyletic group. It is unclear how closely the locust species are related within Locustini, but it is intriguing that several major locust species belong to a relatively small tribe, which could suggest that some components of density-dependent phase polyphenism might be phylogenetically conserved in this clade, similar to the cases in Cyrtacanthacridinae. The monotypic genus Locustana Uvarov, 1921, contains the brown locust, L. pardalina (Walker, 1870), which is one of the major locust species in southern Africa that thrives in the semiarid Karoo region [17]. Because of its agricultural importance, the brown locust has been studied very thor- oughly in terms of its life history and swarm dynamics [ 100] . It is a classic swarming locust, capable of expressing extreme phase characteristics in color, behavior, morphology, and physiology [5, 33, 43] . The phase characteristics of the brown locust were thoroughly investigated early by Faure [33], just soon after the initial formulation of the phase theory [101]. Isolated nymphs are variable in color and exhibit a strong case of homochromy. Green color of the isolated nymphs is associated with high humidity. Crowded nymphs develop characteristic orange and black coloration. Adult morphometric ratios are also strongly affected by crowding. The brown locust displays typical hopper bands and adult swarms, group mating and group oviposition. The genus Oedaleus Fieber, 1853, currently contains 27 valid species, widely distributed across the Old World, from Africa to Asia and to Australia. Ritchie [102] published the most comprehensive revision to date, in which he discussed the taxonomy and biogeography of the genus in detail. This genus is closely related to another genus of interest, Gastri- margus [102]. Several species in Oedaleus are economically important pests, but the Senegalese grasshopper, O. sene- galensis (Krauss, 1877), stands out as the most devastating species [17]. The biology and ecology of this species was recently reviewed by Maiga et al. [103]. This species is widely distributed throughout the tropical and subtropical Psyche 7 regions, and it is often associated with mesoxerophilic habitats and can be categorized as graminivorous [17]. Marching hopper bands and loose swarms of this species have been frequently reported [104], but no quantitative study on behavioral phase is available. Normal green-brown polymorphism similar to other oedipodines is reported from O. senegalensis [105], but it is not clear if density-dependent color change does occur. Ritchie [105] reported that the nymphs in high-density population show a characteristic brown and black coloration. Launois and Launois-Luong [106] declared that O. senegalensis is a true grasshopper because it does not exhibit changes in physiological changes often associated with typical locusts, but gregarious behavior appears to be similar to the locust species. Another member of the genus, O. decorus asiaticus Bei-Bienko, 1941, which occurs widely in Asia, is known to exhibit migratory behavior [ 107] . Recently, Cease et al. [108] showed that rearing density significantly affected physiological responses in this species but failed to demonstrate a direct correlation among rearing density, color plasticity, and behavioral plasticity. The genus Gastrimargus Saussure, 1884, currently con- tains 23 species and 8 subspecies, widely distributed in the tropical grassland of Africa, Asia, and Australasia. Ritchie [109] published the most comprehensive revision to date, in which he discussed the taxonomy and biogeography of the genus in detail and contrasted with the genus Oedaleus which he revised earlier [102], Gastrimargus favors more humid habitats than Oedaleus although both genera are graminivorous [ 109] . Of the 23 species, only three species are reported to be of any economical importance, and they are G. africanus, G. marmoratus, and G. musicus [17]. Of these, only the yellow- winged locust, G. musicus (Fabricius, 1775), is known to express density-dependent phase polyphenism [44]. This species is endemic to coastal and subcostral Australia, where rainfall exceeds 20 inches annually. The most thorough and the only study of the biology and ecology of G. musicus was done by Common [44], and no subsequent study was followed despite its pronounced phase expressions. Isolated and crowded locusts differ in terms of color, morphometric ratios, and behavior. This species displays typical hopper bands, adult swarms, group mating, and group oviposition. Based on the specimens collected from an extensive outbreak that occurred in central Queensland between 1939 and 1947, Common [44] tested the existence of locust phase polyphenism in G. musicus and documented that solitarious nymphs have variable color with green/brown polymorphism and gregarious nymphs are medium to dark brown. He also commented that solitarious populations are often patchily distributed in native pastures, and the outbreak in central Queensland was a result of population buildups over several years under favorable environmental conditions. The monotypic genus Pyrgodera Fischer von Waldheim, 1846, contains the Iranian grasshopper, P. armata Fischer von Waldheim, 1846, which is a peculiar grasshopper, easily identified by its high, arched, and laminate pronotal crest, distributed in the Mediterranean regions [45]. It is a minor pest in this region [17] but included in this paper because it is reported to have plastic response to change in population density [45]. Popov [45] encountered an unusual population of P. armata in South Iran, which showed a tendency to express different phenotypes at high density. The nymphs of this species are typically green at low density, but he found an aggregation of nymphs that have orange and black patterns, similar to the gregarious nymphs of a typical locust. These colored nymphs in high density formed a small marching band, where other nymphs with conspicuous color would join the band and the green nymphs would remain indifferent to the band. The orange and black pattern continued into the adult instar. Although this species does not develop into a full-blown locust swarm, Popov’s observation is indicative of the species expressing density- dependent phenotypic plasticity in terms of both color and nymphal behavior. 2.5. Chortoicetes and Austroicetes. Chortoicetes Brunner von Wattenwyl, 1893, and Austroicetes Uvarov, 1925, are not placed in any tribe within Oedipodinae because they are quite divergent from other members of the subfamily. Fries et al. [99] included both of these genera in their study and found that these two Australian genera form a strong monophyletic group but not related to any other groups within the subfamily. Thus, it is possible to conclude that these two genera are sister to each other but occupy rather an isolated position in Oedipodinae [46]. The Australian plague locust, C. terminifera (Walker, 1870), is the most economically important pest species in Australia [17]. It is found throughout Australia, and its outbreaks are both localized and widespread [96]. Due to its agricultural importance, the life history and population dynamics have been thoroughly studied [110]. The genus Chortoicetes currently contains two species, the nominal species C. terminifera and C. sumbaensis which was initially described as Aiolopus sumbaensis by Willemse [111] based on a female specimen collected from the Indonesian island of Sumba. Hollis [112] transferred this species to Chortoicetes based on tegminal venation, but there was no distinct char- acter to warrant a specific status separate from C. terminifera other than size differences and wing patterns. Although it is difficult to confirm, I suspect that it was a migrant individual of C. terminifera that somehow colonized Sumba, which means that the genus should be considered monotypic. Although C. terminifera displays all the behavioral traits typically associated with locusts, including hopper bands, adult swarms, group mating, and group oviposition [96], it does not change color in response to change in population density [46]. Key [46] showed that adult morphometric ratios are affected by crowding, but the degree of transforma- tion is not as pronounced as other typical locusts. Recently, Gray et al. [9] demonstrated that C. terminifera expresses strong behavioral phase polyphenism, and Cullen et al. [113] showed that the behavioral phase transformation is triggered by tactile stimulation of the antennae. These new studies based on quantitative behavioral assay techniques collectively show that density- dependent phase transformation does not necessarily involve change in color. The genus Austroicetes is probably sister to Chortoicetes and contains 9 valid species. Some members of this genus 8 Psyche can cause severe damages to crops, but the small plague grasshopper (or sometime small plague locust), A. cruciata (Saussure, 1888), used to be considered the worst grasshop- per pest in Western Australia [17]. This species occasionally forms hopper bands and loose adult swarms when popula- tion density becomes high. Key [46] demonstrated that this species and the congeneric A. nullarborensis were capable of displaying density-dependent polyphenism in color, adult morphometries, and behavior. 2.6. Aiolopus simulatrix. The oedipodine genus Aiolopus Fieber, 1853, currently contains 14 species widely distributed throughout the Old World and Australia. Since the revision by Hollis [114], a number of new species have been added to the genus, but this genus still needs to be fully revised. Within Aiolopus, four species (A. simulatrix, A. strepens, A. longicornis, and A. thalassinus ) are recognized as economically important species, but the Sudan plague locust, A. simulatrix (Walker, 1870), is the most devastating species of grain and other crops. Joyce [115] described the biology and behavior of A. simulatrix (as now synonymized A. savignyi ) from East Central Sudan. It forms impressive migratory swarms, but the existence of hopper bands is not well recorded. Nymphs do exhibit density-dependent color plasticity in which nymphs in low density are brown, green, and of a mixture of two colors, whereas crowded nymphs develop a dark pigmentation in pronotum, wingpads, and hind femora [41]. Although there has not been an explicit experiment to study the effect of density in A. simulatrix, Heifetz and Applebaum [47] did such an experiment in a related species A. thalassinus. They found that crowding did not result in changes in morphometric ratios or color but affects behavior and other physiological responses such as CO 2 release and carbohydrate and lipid levels. Thus, it is possible that A. simulatrix may respond similarly to the change in density if it is subjected to a controlled experiment. 2.7. Calliptamus italicus. The genus Calliptamus Serville, 1831, currently contains 15 extant species, and it is widely distributed from northern Africa to Europe and into Russia and China. Of the 15 species, only C. italicus (Linnaeus, 1758) is known to swarm, and it is the only known swarming locust in the subfamily Calliptaminae [17]. It forms narrow and long hopper bands (6-2800 m in length, 3-70 m in width) [116], and the adults form typical migrating swarms. Unlike the classic locusts, nymphal color is not affected by change in the population density [48], but nymphal behavior does appear to be affected [49] although quantitative behav- ioral assays have not been applied to this species. This species exhibits physiological responses to the change in density because the locusts reared in a crowded condition mature more rapidly than the ones reared in an isolated setting [5]. Adults also respond morphometrically, and gregarious adults have much longer tegmina than solitarious adults [50, 51]. 2.8. Dociostaurus marrocanus. The gomphocerine genus Dociostaurus Fieber, 1853, contains three subgenera and 26 species and is widely distributed in the palearctic region. The Moroccan locust, D. marrocanus (Thunberg, 1815), is the only species in the genus known to express an extreme form of density-dependent phase polyphenism in color and morphology in both nymphal and adult stages [5]. Isolated nymphs are yellowish or olive brown with three very distinct black spots on the upper part of hind femora, but crowded nymphs develop orange color in the head and pronotum with faded or no black spots on the hind femora [52]. Gregarious adults are larger in size and have longer tegmina and shorter hind femora than the solitarious ones [53]. It used to be very difficult to rear D. marrocanus in a colony setting [117], but recently there has been an advance in this aspect [118]. Characteristic hopper bands and adult swarms are well documented in this species [5, 17, 52]. This species is highly polyphagous and causes significant agricultural damages in the many countries in the Mediterranean zone [119]. However, the Moroccan locust appears to be very selective in terms of its habitat preference; it is often associated with an ecotonal zone between foothills and valleys, at a range of altitudes of 400-800 m above sea level, with dry- steppe vegetation [117]. The habitat destruction has decreased the severity of outbreak in several developed countries so much, so that the locusts never produce swarms in some cases. Nevertheless, this species is still a major pest species in Afghanistan, Iran, Algeria, Morocco, Uzbekistan, and southern Kazakhstan [117]. 2.9. Rhammatocerus schistocercoides. The gomphocerine genus Rhammatocerus Saussure, 1861, currently consists of 18 species, mostly distributed in the Central and South America. The status of many species is uncertain and the genus is in need of a taxonomic revision although several species in this genus are agriculturally important pest species, and the Mato Grosso grasshopper, R. schistocercoides (Rehn, 1906), stands out as the most serious one. It is found in the shrub-like and wooded savannas in South America, and two of the most affected areas include the Brazilian States of Mato Grosso and Rondonia and the Colombian States of Casanare, Meta, and Vichada [54]. The Mato Grosso grasshoppers regularly form very impressive hopper bands [120] and adult swarms [121], but the effect of population density has not been systematically studied. It is unclear if isolated nymphs would behave any differently from crowded ones. Ebratt et al. [55] reared nymphs in isolated and crowded settings and reported that nymphs were green at low density, but red or brown at high density, which also corresponded with the change in morphometric ratios. However, Pierozzi and Lecoq [54] did not find any morphometric differences in the adults collected from high and low densities and suggested that this species should be considered a grasshopper, not a locust, although they recommended that a more thorough investigation on the expression of locust phase needs to be done in this species. This species is highly variable in terms of color, and Lecoq and Pierozzi [122] documented the color change from brown to green upon sexual maturation. 3. Other Pest Grasshopper Species Pener and Simpson [2] list 23 acridid species that show elements of density- dependent polyphenism, which is an Psyche 9 extended list from Song [4]. In addition to S. gregaria and L. migratoria, the species that I discuss in the previous section are the ones that exhibit cohesive migration groups and density-dependent phenotypic plasticity although the degree of expression is quite variable across species. The Rocky Mountain locust, Melanoplus spretus (Walsh, 1866), used to be the most devastating locust species in North America before it abruptly became extinct in the early 20th century [123]. It is likely that M spretus displayed locust phase polyphenism [124], but most of the data collected for that species predate the formulation of the phase theory [125], and therefore I do not discuss this species in this paper. In this section, I talk about the remaining four species and one species not mentioned by Pener and Simpson [2]. 3.1. Melanoplus. The melanopline genus Melanoplus Stal, 1873, is one of the largest acridid genera containing 243 valid species. No comprehensive revision of this genus is available to date. Many species have very narrow geographic ranges, but some occur throughout North America. Two species that are reported to have density-dependent polyphenism by Pener and Simpson [2] are the migratory grasshopper, M. sanguinipes (Fabricius, 1798), and the differential grasshop- per, M. differentialis (Thomas, 1865). Both species have been reported to display hopper bands and adult swarms that migrate under a very high-density condition in the first half of the 20th century [57, 59, 126]. Crowding does induce melanization in nymphs [58] in M. sanguinipes , but morphometric ratios are not affected. A large body of literature is devoted to the biology and ecology of these two species due to their economical importance [60], but none of the available studies has definitely demonstrated the existence of locust phase polyphenism in these species. Therefore, it would be fair to categorize them as outbreak grasshoppers. 3.2. Gomphocerus sibiricus. The gomphocerine genus Gom- phocerus Thunberg, 1815, contains 8 valid species mostly distributed in the Old World, except one Brazilian species G. semicolor, whose taxonomic status is questionable. Among these, the Siberian locust, G. sibiricus (Linnaeus, 1767) (which was sometimes referred to as Aeropus sibiricus before Aeropus was synonymized under Gomphocerus ), is one of the most economically important pest species in Russia [5]. This species is restricted mainly to xerophilous forest margins [56] and is prone to outbreak. However, there is no documented report of G. sibiricus responding to population density, suggesting that its common name has been misapplied. 3.3. Ceracris kiangsu. The genus Ceracris Walker, 1870, con- tains 12 described species which are distributed throughout China. The Orthoptera Species File currently places the genus in the tribe Parapleurini of the subfamily Oedipodinae [127], but Chinese researchers have always placed it under Arcypteridae [128], which is a junior synonym of the tribe Arcypterini of Gomphocerinae. The genus includes a few economically important species, and the yellow-spined bamboo locust, C. kiangsu Tsai, 1929, is known to be the most important agricultural pest of bamboos [129]. Earlier studies described the nymphs and adults to be gregarious [130, 131] and also reported the migrating bands of the late instar nymphs [131], These earlier studies led Song [4] and Pener and Simpson [2] to include C. kiangsu as one of the species exhibiting a certain level of density-dependent phase polyphenism, but in fact, there is no definitive report of this species being able to change color, morphology, or behavior in response to change in population density. Based on published data, it is possible to deduce that C. kiangsu specializes in feeding on bamboo, and its life history is intimately associated with the bamboo forest. Recent studies have shown that C. kiangsu is attracted to human urine possibly to supplement sodium and nitrogenous compounds which are lacking in bamboos [132], and some have advocated the use of human urine to bait and control this pest [ 133] . All available data point to a conclusion that C. kiangsu is an outbreak species but does not fit the definition of a locust. 3.4. Coscineuta virens. The genus Coscineuta Stal, 1873, currently contains 8 valid species, and it is the only member of the basal proctolabine tribe Coscineutini [134]. Coscineuta is widely distributed in South America, but the Moruga grasshopper, C. virens (Thunberg, 1815), is currently restricted to the southeastern region in Trinidad. Other specimens of this species are known from Guyana and Uruguay, but there is no report of recent occurrence [61]. The Moruga grasshopper, also locally known as Courtac, has been a principal acridid pest of Trinidad feeding on a wide variety of crops including citrus, coffee, cocoa, mango, cassava, and several vegetables [61]. This species is of particular interest because it is known to be gregarious in all stages of life. Nymphs are characteristically colored black and yellow, reminiscent of typical pyrmorphid nymphs, and form very dense and mobile marching bands. Because of this locust-like behavior, Popov et al. [61] examined the existence of density-dependent phase characteristics in this species but found that this species was not affected by isolation or crowing in any meaningful way. In fact, the species appeared to be always in the “gregarious phase” at least in terms of behavior. No followup study has been done on this interesting species of grasshopper. 4. Evolution of Density-Dependent Phase Polyphenism in Acrididae Locust phase polyphenism has evolved multiple times within Acrididae. The convergent evolution of this phenomenon should not be understated. Only a handful of species are capable of expressing locust phase polyphenism out of more than 6400 valid species of Acrididae. In other words, only about 0.29% of known acridids (19 legitimate locust species out of 6444 valid acridid species) can be categorized as locusts. The proportion of the locusts that express full- blown phase polyphenism is even smaller. Based on the present paper, it is possible to conclude that locust phase polyphenism has evolved only in four acridid subfamilies, Cyrtacanthacridinae, Oedipodinae, Gomphocerinae, and Calliptaminae, out of 24 currently recognized subfamilies. 10 Psyche Within each subfamily (except Calliptaminae which only contains one locust species), it has evolved multiple times. Although the ultimate expression of locust phase, density- dependent phenotypic plasticity leading to gregarization and migration, is similar across different locust species, the specific mechanisms behind phase transformation are quite variable. In fact, the deep understanding we have gained through studying S. gregaria and L. migratoria is probably not directly applicable to many nonmodel locust species. This perspective is quite different from a traditional view of studying locusts in which researchers used to look for specific physiological phase characteristics such as changes in color and morphometric ratios in the species in question to determine whether it is a “true locust” or not [135]. The more appropriate view in light of the contemporary definition of locusts should be based on the presence of any density- dependent phenotypic plasticity whether the expression is morphology, physiology, or behavior, or any combination of these. From a taxonomic point of view, an interesting general pattern emerges from the present paper. Typically, locust species often belong to larger taxonomic groups in which most species are not locusts. For example, the Italian locust is the only locust species out of 15 Calliptamus species, and the Moroccan locust is the only locust out of 26 Dociostaurus species. Schistocerca contains only four locust species out of 50 species, all of which are nonswarming sedentary species. This pattern can also be extended to monotypic genera such as Locusta and Locustana, both of which belong to Locustini which contains 72 species, most of which are sedentary grasshoppers. Similarly, the monotypic genus Chortoicetes forms a monophyletic group with Austroicetes which includes nonswarming species. There is no known case of every species of a given taxonomic group being locusts. Every species in a given taxonomic group (whether a genus or a tribe) is closely related phylogenetically and must be very similar to each other morphologically, biologically, and ecologically. But, only a small proportion of a given taxonomic group expresses locust phase polyphenism. What makes some species locusts while other species in the same taxonomic group remain as regular grasshoppers? Do the nonswarming species in these taxonomic groups have the potential to develop locust phase polyphenism? These are certainly very difficult questions to answer, and the obvious answer would be “we do not know.” Locusts are exceptionally adapted to their local environments, and these locust species may simply have the best combination of the traits that make them the most successful, compared to other species in the same taxonomic groups, or there may be some species that are capable of becoming locusts, but the environmental conditions are simply not conducive to the expression of locust phase polyphenism, and we cannot know whether one would be a locust or not a priori. For example, the recent outbreak of S. interrita was not anticipated because the species was not known to be a locust, but the El Nino phenomenon created an excep- tionally favorable environment for the species to express its hidden potential to express locust phase polyphenism [29]. In addition to the general pattern that only a small proportion of species in a given taxonomic group expresses locust phase polyphenism, there is another interesting pat- tern which is not readily noticeable unless one understands the phylogeny of these locusts. Although locust phase polyphenism has evolved convergently, its evolution does not appear to be totally random especially when the phase characteristics of closely related locusts are examined. There are four cases in which there are multiple locust species occurring in supposedly monophyletic groups. They are the locust species in the Schistocerca , Nomadacris-Patanga- Austracris-Valanga, Locustini, and Chortoicetes- Austroicetes clades. Phase-related characters are remarkably similar across different locust species within each monophyletic group (Tables 1 and 2). For instance, the locust species within Schistocerca all exhibit a similar form of density-dependent phenotypic plasticity in color, morphology, physiology, and behavior. They all behave very similarly at high population density and prefer dry habitat and herbaceous plants. Although in the same subfamily, the locust species in the Nomadacris-Patanga-Austracris-Valanga clade behave quite differently from Schistocerca. Adult swarms are prominent in this clade, but hopper bands are only weakly or not at all expressed. These species exhibit neither group mating nor group oviposition, and they distinctly prefer grassland habitats and grasses. The locust species in Locustini also favor grasses but have broader habitat preferences. They all express typical swarm dynamics both as nymphs and as adults and show pronounced density- dependent phenotypic plasticity in many traits. The Chortoicetes-Austroicetes clade belongs to the same subfamily as Locustini, thus the locust species in this clade show similar ecological characteristics but do not change color at high density. Throughout the locust literatures, comparisons among the locust species belonging to different taxonomic groups have seldom been made. The reason for this lack of comparative studies may be due to the fact that several of these locust species are monotypic and thus assumed to be somewhat unique. Although different locust species may not always form a monophyletic group within each clade, it is important to understand that the evolution of locust phase polyphenism is shaped by the shared ancestry and the adaptation to local environmental conditions. Lor example, Song and Wenzel [11] showed that N. septemfasciata, P. succincta, and A. guttulosa form a monophyletic group based on morphological characters and that the individual compo- nents of locust phase polyphenism evolve at different times and its full expression is achieved when these components are expressed together. Because of the shared ancestry, these locust species exhibit the same density- dependent plastic responses, but they also exhibit unique traits and ecological adaptations because they are specifically adapted to their local environments. Another example can be found in Schistocerca. Many sedentary species in the genus Schistocerca display density-dependent color plasticity [65-69], which indicates that the physiological mechanisms behind this plastic reaction norm may be a phylogenetically conserved ancestral trait. Thus, the development of conspicuous nymphal coloration in the gregarious phase of S. gregaria. is Psyche 11 not a novel trait in locusts, but an expression of ancestral phenotypic plasticity [4] . These examples are, however, based not on experimental data, but on the fragmentary reports published in various literature sources [11]. Nevertheless, it demonstrated the importance of a phylogenetic perspective in understanding the evolution of locust phase polyphenism. 5. A Call for a Phylogeny-Based Research Program in the Study of Locust Phase Polyphenism For the last century since the formulation of the phase theory, especially for the last two decades, tremendous advances have been made in the study of locust phase polyphenism using S. gregaria and L. migratoria as model systems. Despite the deep understanding we have gained based on a model- based approach, we know surprisingly little about other nonmodel locust species. In this paper, I show that many of the nonmodel locusts exhibit different forms of locust phase polyphenism and what we know about the model species do not necessarily translate to these nonmodel species. As a parallel illustration, we have accumulated an enormous body of information on the making of a fruit fly, Drosophila melanogaster, a very specialized dipteran species, but this does not mean that we have learned everything about the extremely diverse order of Diptera, nor does it mean what is known about the fruit fly is directly applicable to other flies. The model-based approach in studying locust phase polyphenism is undoubtedly invaluable, but a much richer understanding of this phenomenon can be gained if it is complemented with a phylogenetic approach. Applying a phylogenetic perspective to the study of speciation, adaptation, behavioral ecology, and character evolution has often resulted in deeper and more comprehen- sive understandings of the subject [136]. A phylogeny-based research framework in locust phase polyphenism can allow us to investigate relevant questions such as reconstructing ancestral state of individual components of locust phase, tracing the origin and transformation of different phase - related traits, and testing correlations between different phase-related traits. This approach can predict that non- swarming species might be capable of expressing phase polyphenism when favorable environmental conditions arise and also help form testable hypotheses on the phase expres- sions of nonmodel locust species that are closely related to the model species. For instance, what we know about 5. gregaria can form a basis for studying other locust species in Schistocerca because of their phylogenetic relationships. Take the mechanoreceptors present in the outer face of hind femora for an example. The behavioral phase transformation can be achieved by stimulating these mechanoreceptors in S. gregaria [137]. An informed null hypothesis then maybe that S. piceifrons or S. cancellata can also respond to density in a similar way. Cullen et al. [113] recently showed that the tactile stimuli are sensed by the antennal receptors in C. terminifera , rather than hind femora. This suggests that what is known about S. gregaria might not apply to C. terminifera, but what we gain from studying C. terminifera can form a basis for studying Austroicetes cruciata because of their phylogenetic relationships. It is thus possible to predict that A. cruciata is likely to respond to antennal stimulation rather than leg stimulation. Likewise, what we know about L. migratoria is a good starting point for understanding the locust phase polyphenism in L. pardalina, G. musicus, and O. senegalensis because they all belong to Locustini. By studying both similarities and differences among different locust species in the same monophyletic groups, we can gain greater understanding of the evolution of locust phase polyphenism. This phylogeny-based research program certainly has several challenges. Reconstructing a robust phylogeny is always a difficult endeavor laden with problems of taxon and character sampling, and numerous assumptions about phylogenetic reconstruction methods. For locust research, the problem is exacerbated because the use of mitochon- drial genes, which is commonly employed in inferring the relationships among closely related species, is difficult because Acrididae is known to be severely affected by nuclear mitochondrial pseudogenes [138-140]. Generating data on density-dependent phenotypic plasticity in explicitly controlled laboratory settings for all species in a given monophyletic group is extremely challenging. Even the cost of maintaining colonies of different species would be prohibitively high. Thus, this research program would necessarily have to be a long-term international collaborative project. Despite all these difficulties, I would still argue that this phylogeny-based approach would considerably expand upon the insights we have gained from the current model-based approach. In this paper, I have identified four candidate monophyletic groups which contain multiple locust species and many nonswarming species. Of these, I argue that the locust research community should initially focus on Schistocerca and Locustini. We can take advantage of what we have learned so far based on the study of S. gregaria and L. migratoria and begin to understand the evolution of locust phase polyphenism in other locust species in these two groups with phylogeny-based, informed predictions. Exciting results from this research program will eventu- ally form a basis for investigating other nonmodel locust species. 6. Conclusion In this study, I have performed a literature review focusing on locust phase polyphenism of nonmodel locust species. The most striking finding is how little we know about these nonmodel locust species. So far, there have been only three locust species (S. gregaria, L. migratoria, and C. terminifera ) that have been investigated using modern quantitative behavioral assay techniques [2, 8, 9]. We do not know what specific stimulus triggers phase transformation in other species. Endocrine responses, biochemical changes, and molecular expressions in response to change in density are completely unknown for most of the locust species. This lack of knowledge means that there are many new exciting findings and insights waiting to be discovered. The major 12 Psyche theme of this paper is that there are many ways to become locusts, and the evolution of locust phase polyphenism has to be understood through the lens of phylogeny. We have learned a great deal about the specific mechanisms of phase transformation of model locust species over the past few decades. Now, it is time to expand the study of locust phase polyphenism to these nonmodel locust species to gain a deeper understanding of this fascinating phenomenon. Acknowledgments The author thanks Alex Latchininsky for allowing him to think about this subject in depth. Greg Sword generously shared his unpublished data. Greg Sword and two anony- mous reviewers provided valuable comments on the earlier version of this paper. This work was supported by the National Science Foundation Grant no. DEB-0816962. References [1] M. P. Pener, “Endocrine aspects of phase polymorphism in locusts,” in Invertebrate Endocrinology, Endocrinology of Insects, R. G. H. Downer and H. 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Hindawi Publishing Corporation Psyche Volume 2011, Article ID 324130, 9 pages doi:10.1 155/201 1/324130 Review Article Distribution Patterns of Grasshoppers and Their Kin in the Boreal Zone Michael G. Sergeev 1,2 1 Department of General Biology and Ecology, Novosibirsk State University, 2 Pirogova Street, Novosibirsk 630090, Russia 2 Laboratory of Insect Ecology, Institute of Systematics and Ecology of Animals, Siberian Branch, Russian Academy of Sciences, 1 1 Frunze Street, Novosibirsk 630091, Russia Correspondence should be addressed to Michael G. Sergeev, mgs@fen.nsu.ru Received 1 August 2010; Accepted 17 September 2010 Academic Editor: Alexandre Latchininsky Copyright © 201 1 Michael G. Sergeev. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. The distribution patterns of Orthoptera are described for the boreal zone. The boreal fauna of Eurasia includes more than 81 species. Many of them are widely distributed. The monotypic genus Paracyphoderris Storozhenko and at least 13 species are endemics or subendemics. About 50 species are known from boreal North America. Four endemic species are distributed very locally. Relationships between the faunas of the Eurasian and North American parts of the boreal zone are relatively weak. The boreal assemblages are usually characterized by the low levels of species diversity and abundance. Grasshoppers and their relatives occupy almost exclusively open habitats, such as different types of meadows, mountain steppes and tundras, clearings, openings, bogs, and stony flood plains. The local endemics and subendemics are found only in some habitats of the eastern part of Eurasia and the north-western part of North America. Retrospective and prospective of the boreal fauna of Orthoptera are also discussed. 1. Introduction The boreal zone is the huge area in the Northern Hemi- sphere where the coniferous forests form the main type of vegetation [1], average temperatures are relatively low (mean temperatures of the warmest month vary from 6.5° C to 19°C, the same for the coldest month, from -6°C to -49° C), and annual precipitation varies from relatively high near Atlantic and Pacific oceans (more than 1600 mm per year) to very low in the inner parts of the continents (less than 200 mm) [2]. From the ecogeographic point of view, in Eurasia, this life zone almost corresponds with the so-called taiga area [1, 2]. In North America, it occupies the significant part of the so-called Spruce- Caribou Biome [3] and almost corresponds to the united boreal life zone sensu Merriam [4]. From the zoogeographic point of view, in Eurasia, the boreal zone almost coincides with the Eurosiberian Region (or Subregion) (without the Subarctic and Arctic areas) erected mainly on the basis of the species distribution analysis [5-8]. In North America, it more or less coincides with the so-called Canadian Region [5]. The climatic conditions and dominated coniferous forest habitats are not comfortable for most grasshoppers and their relatives. The general level of their diversity is relatively low [7, 9-12]. Ecological peculiarities and adaptations of most species associated with the boreal zone are almost unknown [9, 11]. There are no species inhabiting coniferous trees and shrubs. Almost all forms prefer openings with herbaceous vegetation and meadows. Several species (mainly from the tribe Melanoplini and some widely distributed katydids) usually settle shrubs along forest edges [9, 13, 14]. A few forms prefer herbaceous microhabitats under a coniferous forest canopy. Among them are Podismopsis silvestris Storozh. [15] and, in some parts of its range, Prumna primnoa (F.d.W.) (our unpublished data). Many species are univoltine with overwintering eggs, but in North America several forms are semivoltine: they pass the first cold season as eggs and the second as hoppers [16]. Their development is limited by a relatively short warm season. This results in more or less simultaneous development of almost all species [ 13] . Besides that, many local grasshoppers prefer to lay egg pods on leaves, in leaf axils, grass stems, rotten woods, leaf litter, and in the upper soil layer [11, 13, 14, 17]. 2 Psyche Uvarov [13] emphasized that the boreal area can be regarded as devoid of grasshoppers. However, there are different types of meadows, openings, and bogs that can be settled by some species. Beside that, mountains are well developed in different parts of the boreal zone, especially in the eastern part of Eurasia and in the western part of North America. A complicated relief of the mountain systems provides a level of landscape diversity comfortable for many grasshoppers and their kin. There are many dry and warm habitats with steppe -like vegetation, especially along southern slopes of ridges, and alpine and subalpine meadows, often with shrubs, above the timberline. As a result, the boreal zone is populated by both endemic taxa and extremely abundant species which can form outbreaks during droughts. The main aim of this paper is to establish general patterns of Orthoptera distribution in the boreal zone. 2. Methods and Materials Both qualitative and quantitative data were used. The analysis of geographic distribution was based on published and unpublished species range maps. Species data points for Eurasian Orthoptera were plotted onto base maps, usually on a scale of 1 : 25,000,000. My own collections, the collections of different museums, and published data were used [6, 7]. Besides, several maps published by Albrecht [18] for Fennoscandia were adopted. I also analyzed the published species range maps of North American Orthoptera [10, 11, 16, 19, 20], The analysis of ecological distribution was based on quantitative samples collected in natural and seminatural habitats. Samples captured during a fixed period of time were made in every habitat investigated [6,21]. Using this method, insects were caught with a standard net over a period of 10-30 minutes. Results for every habitat were recalculated for an hour. This method allowed us to obtain repeatable and comparable results for different regions and years. These samples were collected in some parts of the Eurasian boreal zone by the expeditions of the Department of General Biology and Ecology (Novosibirsk State University) and the Laboratory of Insect Ecology (Institute of Systematics and Ecology of Animals) from 1972 to 2003. Several published papers [14, 15, 22-28] describing orthopteran assemblages in different parts of the boreal zone were also used. 3. Geographic Distribution The general distribution of grasshoppers and their kin in the Holarctic Region reflects the southern thermophilic character of these insects and their common association with open habitats, such as different grasslands, openings, bogs, and so forth [7, 11-13]. Grasshoppers are not typical of the tundra life zone [16, 29, 30] although a few species occur in the southern tundra and forest tundra. The only species penetrating in the northern tundra of North America is Aeropedellus arcticus Heb. [19]. The most common grasshopper of the tundra as a whole is Melanoplus frigidus (Boh.). The fauna of the boreal life zone includes about 130 species of Orthoptera. Many of them are distributed only in its southern part. Hundreds of species are found southwards, in the nemoral (broad-leaf) forest, steppe, and prairie life zones [7]. Bey-Bienko [9] analyzed the general distribution patterns of Orthoptera in the boreal zone of the former USSR. He noted occurrence of 31 species in its western part and 44 in the eastern one (51 species in total). Prevalence of species preferring grass layers of local ecosystems was also emphasized. Bey-Bienko described some differences between orthopteran distribution patterns in the western (where dark coniferous forests dominate) and eastern (mainly with light coniferous forests) taiga. In the western part, grasshoppers usually settle openings and bogs. In the eastern part, local species settle both the same set of habitats as in the western taiga and more or less dry plots (steppes, dry meadows), but often on the higher level of abundance. They also can survive winters with very low temperatures. The fauna of the boreal part of Eurasia includes more than 81 species of Orthoptera, about 3/4 of them are the members of the family Acrididae. Many species are widely distributed in the boreal zone of Eurasia, usually from Atlantic Ocean to the Pacific one (Figures 1 and 2). Among them are Podisma pedestris (L.), Melanoplus frigidus, Aeropus sibiricus (L.), Aeropedellus variegatus (F.d.W.), Stethophyma grossum (L.), Bryodema tuberculatum (F.), Chrysochraon dispar (Germ.), Omocestus haemorrhoidalis (Charp.), O. viridulus (L.), Chorthippus montanus (Charp.), Ch. albo- marginatus (Deg.), Metrioptera brachyptera (L.), Decticus verrucivorus (L.), Tetrix subulata (L.), and T. fuliginosa (Zett.). Besides, there are many species which populate either the western (European) part of the zone {Chorthippus pullus (Phil.), Oedipoda caerulescens (L.), Sphingonotus caerulans (L.), Tetrix undulata (Sow.), and Pholidoptera griseoaptera (Deg.)), or the southern Siberian Mts. {Montana tomini (Pyln.), Stenobothrus eurasius Zub., and Bryodema holdereri Kr.), or its eastern part {Zubovskya koeppeni (Zub.), Chor- thippus fallax (Zub.), Sphagniana ussuriana (Uv.), and Tetrix japonica (I. Bol.)) (Figures 1-3). They often occur in the northern parts of the taiga and, in some cases, penetrate in the tundra, especially either in the European or Beringian ones. The sparse local populations of the Migratory locust {Locusta migratoria L.) are also found in the European taiga area [ 18] . Almost all widely distributed species are associated with either the subboreal areas (especially with the forest- steppes, steppes and semideserts in the inner territories of Eurasia) or the deciduous forest life zone of Europe or the Far East. In the boreal zone, they often settle very dry habitats, for example, openings in pine forests on sandy soils. Some widely distributed grasshoppers (e.g., Aeropus sibiricus, Melanoplus frigidus, and Podisma pedestris ) have isolated populations in the mountains of south temperate Eurasia (from Pyrenees to Central Asia) (Figure 2) [31, 32]. The genus Par acypho denis Storozhenko (with one species — P. erebeus Storozhenko) (Figure 1) and at least 13 species are endemics or subendemics of the boreal zone of Eurasia. All of them are distributed only in its eastern part. Some endemic species have relatively broad ranges Psyche 3 ...... i --- 2 3 • 4 — - 5 _... 6 ★ 7 ■ 8 Figure 1: Distribution of Arphia conspersa (1), Sphagniana sphagnorum (2), Aeropodellus arcticus (3), Xanthippus brooksi (4), Tetrix fuliginosa (5), Chorthippus fallax (6), Ch. shantariensis (7), and Par acypho denis erebeus (8) relative to the boreal zone (cross- hatching) (see text and references for details). The boundaries of the boreal zone based on [1, 2, 5] with some minor changes and simplification. The basic map is “Northern Hemisphere of Earth (Lambert Azimuthal projection)” by Sean Baker from http://commons.wikimedia.org/wiki/ file:Northern_Hemi- sphere_LamAz.png, under the CC-by-2.0 license. (usually from the Enisej River basin to Pacific ocean): Prumna polaris Mir., Zubovskya koeppeni, Podismopsis jacuta Mir., and P. gelida Mir. (Figures 2 and 3). Their local populations can be usually found in the mountains of South Siberia and Mongolia and in the southern tundra of north- eastern Siberia. The others are distributed locally ( Prumna specialis (Mistsh.), P. arctica (Zhang et Jin), P. montana (Storozhenko), Chrysochraon amurensis Mistsh., Podismop- sis silvestris, P. insularis Mistsh., Chorthippus shantariensis Mistsh., and Paracyphoderris erebeus) (Figures 1-3). Among them are both insular ( Podismopsis silvestris — Sakhalin, P. insularis and Chorthippus shantariensis — Shantar Islands) and montane endemics ( Prumna specialis, P. montana — Sihote-Alin, and P. arctica — Greater Khingan). It is interest- ing that the majority of endemics are from two acridid tribes: Melanoplini (Figure 2) and Chrysochraontini (Figure 3). Besides, in the southern part of the Russian Far East, there are two montane endemics, namely, Hypsopedes kurentzovi B.-Bienko and Prumna kurentzovi (Mistsh.), which have populations outside the boundaries of the boreal zone, but above the timberline. All endemics have relatively short or no wings. Hence, their possibility to migrate is very limited. Thus, in the boreal zone of Eurasia, the main area of diversity and endemism of Orthoptera is in the eastern (Pacific) part. Its endemics are mainly close relatives of forms associated with the Manchurian Subregion [7]. The general patterns of Orthoptera distribution in North America were described by Vickery [10] and Kevan [33]. Both authors noted that there are several widely distributed species, mainly from Acrididae and Tetrigidae. Vickery [10] emphasized that only a few species are found in the tundra of this continent. More than 50 species are known from the boreal zone of North America [10, 11, 19, 20, 34]. About 57% are members of the family Acrididae. There are at least 5 species of crickets (both Gryllinae and Nemobiinae). Another specific feature is presence of several species of the genus Melanoplus Stal. Many species are widely distributed in the boreal zone of North America, usually from Pacific Ocean to the Atlantic one. Among them are Stethophyma gracile (Scudd.), S. lineatum (Scudd.), Chloealtis conspersa (Har- ris), Ch. abdominalis (Thomas), Chorthippus curtipennis (Harris), Pardalophora apiculata (Harris), Camnula pellucida (Scudd.), Trimerotropis verruculata (Kirby), Melanoplus bore- alis (Fieb.), M. fasciatus (F. Walk.), M. sangunipes (Fabr.), and Tetrix subulata (F.) (Figures 2 and 3). They often occur in the northern parts of the taiga and, in some cases, penetrate in the tundra. Aeropedellus articus is almost 4 Psyche — i - - 2 A 3 □ 4 o 5 - -v/' 6 • 7 ■ 8 ★ 9 Figure 2: Distribution of the Melanoplini grasshoppers: Melanoplus borealis (1), M. firgidus (2), M. gaspesiensis (3), M. madeleineae (4), M gordonae (5), Prumna polaris (6), P. specialis and P. montana (7), P. arctica (8), and P. kurentzovi (9) relative to the boreal zone. unique grasshoppers penetrating in the northern tundra of north-western North America (Figure 1). Almost all widely distributed species are associated either with the subboreal areas, especially with the prairies and forest-prairies in the inner territories of North America, or with the mixed and deciduous forest areas of the Atlantic coast (Figures 2 and 3). Besides, there are several species which occupy the western part of the zone ( Arphia conspersa Scudd. and Encoptolophus costalis Scudd.) (Figure 1). Two North American species may be characterized as subendemics of the boreal zone with relatively broad ranges. Aeropedellus arcticus is distributed in the north-western part of the continent (Figure 1). This grasshopper prefers different tundra habitats [16]. The second species is the katydid Sphagniana sphagnorum (F. Walk.) which occurs in the central part of the boreal life zone. The main part of the range of Xanthippus brooksi Vickery (Figure 1) is in the western part of the boreal zone, but the local population is found near the delta of the Mackenzie River, outside this zone [10, 16]. Four endemic species are distributed very locally. Melanoplus gordonae Vickery is found in the vicinities of Fairbanks (Alaska) (Figure 2). Bruneria yukonensis Vickery is distributed in the southern part of Yukon [16, 28]. Melanoplus gaspesiensis Vickery and M. madeleineae Vickery and Kevan are limited by the small territories on the Atlantic coast (Figure 2). The latter occupies the Magdalen Islands. Both species are close to M. borealis [35]. Unlike the endemics of boreal Eurasia, the North American have either short or well developed wings ( Xanthippus brooksi and Melanoplus gordonae). Thus, in the boreal zone of North America, the two very weak regions of Orthoptera endemism are in the western and eastern parts. Their relatives are quite different from the zoogeographic and taxonomic points of view and occur in boreal and subboreal Eurasia ( Sphagniana sphagnorum and Aeropedellus arcticus ), in the Great Plains and the Rocky Mountains ( Xanthippus brooksi and Bruneria yukonensis), and in the temperate areas of North America ( Melanoplus gordonae). Compared to the fauna of the boreal Eurasia, the local fauna of Orthoptera looks like impoverished. The main reasons of this distinction can be significant difference both in the areas occupied by the boreal zone in North America and Eurasia (correspondingly about 5.4 X 10 6 and 8.4 X 10 6 km 2 , based on soil distribution patterns [36]) and in the Pleistocene history of the regions. For instance, during the last glacial maximum, the northern half of North America was covered by the ice sheet (except some areas in Beringia) [37]. On the contrary, in Eurasia, the Asian part was almost free from plain ice sheets, but relatively small ice sheets developed in mountains and in the north-western part. These reasons do not exclude one another. Relationships between the orthopteran faunas of the Eurasian and North American parts of the boreal zone are relatively weak, but they are more significant than for the whole Palaearctic and the whole Nearctic Regions. There are only two common species: Tetrix subulata and Psyche 5 Melanoplus frigidus (except invasive forms, such as Roeseliana roeselii (Hagen.)). Moreover, Melanoplus frigidus occurs only in the north-western part of North America. Several North American species have close relatives in Eurasia: Chorthippus curtipennis is the member of the Chorthippus parallelus group, and Aeropedellus arcticus is similar to Ae. variegatus. Besides, there are some common genera. However, these genera can be divided into two groups: the first includes genera distributed mainly in the Holarctic area ( Stethophyma Fisch., Sphagniana Zeun., and Melanoplus Stal), and the second one includes genera ( Conocephalus , Gryllus, Tetrix ) widely distributed in both the temperate and tropical regions. Relationships between genera (e.g., Brune- ria — Stenobothrus, Chloealtis Harris — Chrysochraon Fisch., Ageneotettix McNeil — Dociostaurus Fieb.) are not so evident and should be discussed after taxonomic revisions of these groups. 4. Ecological Distribution The general pattern of ecological distribution of boreal Orthoptera is relatively simple: they prefer different types of meadows, steppes, edges, openings, river valleys, and bogs. However, the quantitative data concerning ecological distribution and assemblages of these insects in the boreal zone are extremely limited. There are several publications for different parts of Eurasia and only one paper for North America. Bey-Bienko [22] was the first orthopterist who described assemblages of Orthoptera in the boreal zone, in the eastern part of West Siberian Plain. He noted the low levels of diversity (4-9 species) in all habitats and relatively high levels of abundance of Chorthippus albomarginatus, Glyptobothrus biguttulus (F.), and Aeropus sibiricus at the dry openings of the local pine forests on sandy soils. The main species over the flood plain meadows were Tetrix subulata, Stetho- phyma grossum, and Chorthippus montanus. Bey-Bienko also emphasized evident localization of all orthopteran populations. Chernyakhovskiy [14, 25] described main parameters for the assemblages of Orthoptera in the middle taiga of European Russia (Pechoro-Ilychskiy State Reserve). The level of species diversity is also low (2-11 species). The maximal numbers of species are found in meadows and clearings. The minimal diversity is in the lower flood plains and bogs. Omocestus viridulus and Chorthippus apricarius (E.) dominate in meadow habitats, whereas Stethophyma grossum is the most abundant form in bogs. In the southern taiga of West Siberian Plain, the orthopteran assemblages investigated include from 3 to 11 species. The general abundance is relatively low. The maximal numbers of registered species and specimens (up to 676 per hour) are found on the meadow terraces. Metrioptera brachyptera (L.), Chorthippus apricarius (E.), and Glyptobothrus biguttulus are the common dominants on the plain and terraces. Stethophyma grossum is abundant in the assemblage of the wet flood plain meadows. The similar pattern is described by Chernyakhovskiy [24] for the vicinities of Tomsk. In the middle taiga of Central Siberia, the level of species diversity is similar [23]. The local assemblages usually include several species of grasshoppers. Chorthippus apri- carius is common in the plain meadow habitats. Tetrix tenuicornis (Sahib.) dominates in the bog ecosystems. The maximal number of species (10) is registered on the stony flood-plains. Glyptobothrus brunneus (Thnb.) [? - M.S.], Chrysochraon dispar , Aeropus sibiricus, and Podisma pedestris are abundant here. The specific, near-polar steppes of north-eastern Yakutia are mainly inhabited by the widely distributed steppe grasshopper [27]. The similar situation is in the dry parts of central Yakutia, in which Chorthippus albomarginatus, Aeropus sibiricus, Glyptobothrus maritimus, and Omoces- tus haemorrhoidalis are the most common species over all meadow and steppe-like habitats. The local openings are characterized by dominance of Podisma pedestris and Melanoplus frigidus. This part of the boreal zone is very specific due to short, but hot and often dry summer season. After several years with droughts, the general abundance of grasshoppers may increase significantly. As s result, they can damage almost all vegetation [38]. In the middle taiga of south Yakutia, the orthopteran assemblages are relatively diverse and include many species (from 11 to 27) [26]. This pattern may be determined by the rather complicated mosaic of mountain slopes, river valleys, and plateaus. Beside that, this area is near the northern boundary of the Manchurian Subregion of the Palaearctic. As a result, some species associated with the broad-leaf forest life zone penetrate northwards. Podismopsis gelida and Aeropedellus variegatus are the common species in the mountain tundra. Dry slopes are mainly inhabited by Melanoplus frigidus and Gomphocerus rufus (L.). Tetrix fuliginosa, Melanoplus frigidus, Chrysochraon dispar, and Podismopsis poppiusi dominate in the different assemblages in the bog and meadow habitats. In the boreal part of Sakhalin, Storozhenko [15] found orthopteran assemblages similar to the continental ones. The species number varies from 1 to 9. The local populations are sparse. The endemic Podismopsis silvestris is the only species inhabiting plots of the spruce forests with green mosses. This grasshopper is found only here. Another endemic distributed in the Pacific part of the boreal zone, namely Aeropus kudia (Caud.), settles all more or less open habitats. Prumna primnoa and Zubovskya koeppeni are dominants on openings. Chorthippus intermedius (B.-Bien.) are the most abundant form in different meadow habitats. Glyptobothrus maritimus (Mistsh.) dominates on the lower flood plains. Berman et al. [28] described ecological distribution and assemblages of grasshoppers in the habitats of the southern part of Yukon. The levels of species diversity and abundance are very low. The first varies from 2 to 8 and the later from 18 to 61 specimens per hour. Bruneria yukonensis and Melanoplus kennicottii Scudd. dominate in different variants of the sagebrush steppes. M. kenni- cotti, M. borealis, M. fasciatus (F. Walk.), and Cloealtis abdominalis are the most abundant grasshoppers in the different mountain tundra. The local endemics, namely Bruneria yukonensis and Xanthippus brooksi, are found in 6 Psyche " - - 1 • 4 2 ★ 5 # 3 Figure 3: Distribution of the Chrysochraontini grasshoppers: Chloealtis conspersa (1), Podismopsis gelida (2), P. silvestris (3), P. insularis (4), and Chrysochraon amurensis (5) relative to the boreal zone. the steppe habitats. The abundance of the first one is relatively high. Thus, compared to the orthopteran assemblages of the southward territories [39, 40], the assemblages described from the boreal zone are usually characterized by the low levels of species diversity and abundance. In this area, grasshoppers and their relatives occupy almost exclusively open habitats, such as different types of meadows, mountain steppes and tundras, clearings, openings, bogs, and stony flood plains. In the main part of the zone, orthopteran assemblages are composed from widely distributed species usually inhabiting the broad variety of life zones and ecosys- tems. The boreal endemics and subendemics are found only in some habitats of the eastern part of Eurasia and the north- western part of North America. However, they are often abundant and may dominate in local assemblages. In Eurasia, the local endemics occupy different open habitats, from the mountain tundras to openings. The only Podismopsis silvestris is found in the spruce forest [ 15] . In North America, the local endemics investigated are associated with the mountains steppes [28]. 5. The Boreal Orthoptera: Retrospective and Prospective As one knows, reconstruction of the past of many taxa faces numerous problems. The most important of them is the shortage of their fossils. This results in development of different hypotheses explaining biogeographic and ecological history of such groups. In the absence of adequate fossil data, an applicable approach may be based on a complex analysis of the limiting factors, adaptations to particular living conditions, and the optimum conditions, which may be evaluated based on the species range shape and the population distribution within the range [6, 41, 42]. A phylogeographic approach also allows us to reconstruct some important events and processes of the past [43-47] . However, these studies should develop on the basis of integration of historical geographic and genetic data [47]. The history of the boreal Orthoptera was discussed in a number of papers. Uvarov [48] noted that the orthopteran fauna of the northern Palaearctic area, especially in Europe, was seriously suffered during last glaciations. He also emphasized the role of “an enormous invasion of strange fauna swept over Europe from the East” (p. 1519). This group is associated with the eastern territory of temperate Asia. Uvarov suggested to call the group “the Angara fauna” and included in it the group Chorthippi (i.e., Chorthippus Fieb. and its relatives), the genera Podisma Berth., Melanoplus Stal, Stethophyma Fisch., Bryodema Fieb., Aeropus Gistl, Podismopsis Zub., and so forth. He also mentioned some relationships between the Angara fauna and the faunas of the southern parts of East Asia. Later Bey-Bienko [9] devel- oped some Uvarovs idea concerning the Angara fauna of Orthoptera. He suggested to separate the so-called Siberian forest meadow group of Orthoptera associated with eastern part of Siberia. It includes at least Podismopsis poppiusi, Chorthippus fallax, and Ch. intermedius (B.-Bien.). Lindroth [49] discussed different aspects of zoogeo- graphic connections between Europe and North America Psyche 7 and emphasized their relative weakness. He noted that more or less evident relationships may be for arctic and subarctic forms and some taxa at “a lower evolutionary stage.” Lindroth also showed the extremely significant role of species invasions due to human activity from Eurasia to North America and vice versa. Lindroth [49] also discussed different hypotheses of earlier transatlantic land-connections. He noted that the continental drift took place too early to trace their biological consequences for the North Atlantic area. Vickery [35] described some possible stages and ways of origination of the North American fauna of Orthoptera. He noted that the distribution of many Orthoptera taxa reflects very old, at least the Tertiary, connections between continents. However, other species, for example, Tetrix subulata and Melanoplus frigidus, could cross the Bering land bridge during the Quaternary period. He suggested that such grasshoppers might survive glaciations (especially the last one) in Beringia where some refugia with relatively mild and dry climate existed. Two endemics of the eastern part of the North American boreal zone look like to evolve (or survive) in small areas which were unglaciated. Sergeev [6, 41 ] noted that the autochthonous component in the boreal zone of Eurasia is weak and associated with its eastern territories, which were unglaciated during the Quaternary period. Usually the autochthonous forms are close relatives of taxa connected with regions of East Asia where the broad-leaf forests, both temperate and subtropical, dominate. The widely distributed species usually inhabit- ing different meadows and steppes could spread over the boreal zone during glaciations when open habitats (tundras, tundra-steppes, and cold steppes) occupied huge territories in North Asia. Several species mainly associated with the nemoral zone of the Far East could distribute during interglacials and the climatic optimum of the Holocene [6, 9, 41]. Beside that, one should note that some data for beetles show that spreading rates of terrestrial insects during glacial-interglacials changes might be enough for their wide distribution [50] . This means that the main events determining the modern character of the boreal fauna could take place during the Quaternary period. Thus, in the boreal zone, grasshoppers and their kin represent groups of different origins. (1) The main part of genera is evidently associated with the southward areas of each continent. Their species can be usually interpreted as more or less recent invaders in the boreal zone, especially in North America. This group also includes the genera widely distributed in both the New and Old World ( Conocephalus Thnb., Gryllus L., Tetrix Latr.). (2) Another group of the genera is associated with the Holarctic Region. These Orthoptera are often cold resistant. They could distribute over the boreal zone from the end of the Neogene. However, the molecular phylogenetic analysis [51] showed that the dispersion time of some taxa from Eurasia to North America (e.g., the ancestors of the North American Stethophyma ) could be considerably earlier than the estimations published [35] . The interchanges between Eurasia and North America could take place many times across the Bering land bridge. Several related genera (e.g., Bruneria McNeil — Stenobothrus Fisch.) demonstrate relatively old connections (probably, associated with first glaciations), on the contrary, two species distributed in North America and Eurasia ( Tetrix subulata, Melanoplus frigidus ) could cross this bridge during the last glaciations. The boreal endemics of Eurasia and North America look like quite different. The first group consists from the species associated with territories not covered by ice sheets during the Quaternary period. Although they are ecologically diverse and prefer various types of habitats (from mountain tundras to openings and meadows), the nemoral origin of almost all of them is evident. The differentiation of possible ancestral forms could be resulted from separation of different types of the forest landscapes (especially the boreal ones) in the end of the Neogene. However, the evolution of the several species of the genus Prumna Motsch. might be determined by the significant level of isolation of local populations and by limited dispersal opportunities. The local endemic of North America can be divided into two pairs. Origin of both can be explained by the refugium distribution during the last glaciations. One pair includes species associated with the north-western part of the continent. The evolution of both forms could take place in the Beringian refugia [35]. This hypothesis is supported by data concerning fossil beetles [52]. Two species of the genus Melanoplus were evidently evolved during the last glaciations when the areas of their origination remained off ice sheets [35]. Hence the distribution patterns of the boreal Orthoptera show that one can estimate the number of stages and sequence of their evolution and interchanges, but do not allow us to determine the exact periods of these processes and the directions of interchanges between two continents. For instance, the main migration direction of Melanoplus frigidus is still debatable [35, 44]. However, last comparative studies of molecular phylogeny of melanopline grasshoppers showed that the main direction dispersal could be from South America to Eurasia [45]. One of the principal results of retrospective views on faunas and populations is the opportunity to forecast their possible changes in the future. If the trend of global warming will hold, the boreal zone will shift northwards and its area will reduce [53, 54]; however, the precipitation will decrease [54]. This should result in the Orthoptera distribution pattern. Grasshoppers occupying the boreal zone will shift the northern boundaries of their ranges northwards, up to Arctic Ocean. Local endemics may be eliminated due to high rates of changes. This is especially important for the high montane forms occurred above timberline, because their native landscapes will disappear. Abundance and diversity of other boreal grasshoppers with isolated populations in mountains and on plain openings and meadows will potentially decrease down to their full elimination [55]. On the contrary, some widely distributed species associated with the steppe and forest steppe life zones will be able to spread northwards along different anthropogenic habitats, such as clearings, roadsides, agri- cultural fields, and pastures [41]. Besides, their abundance may increase and some of them may become potential pests. 8 Psyche Acknowledgments The author benefited from interactions with A. Latchininsky and anonymous reviewers. He wishes to express his sincere thanks to the Russian Federal Programme “Scientific and Scientific-Pedagogical Staff of Innovative Russia” (project no. 02.740.11.0277) and the Programme of the Federal Agency for Education “Development of Research Potentials for Higher Education” (Grant no. 1577) for vital financial support. References [1] L. Hamet-Ahti, “The boreal zone and its biotic subdivision,” Fennia , vol. 159, no. 1, pp. 69-75, 1981. [2] A. G. Isachenko, Landshafty SSSR , Leningrad University, Leningrad, Russia, 1985. [3] V. E. Elton, The Ecology of North America , University of Illinois Press, Urbana, IL, USA, 1963. [4] C. H. 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Sergeev, “Conservation of orthopteran biological diver- sity relative to landscape change in temperate Eurasia,” Journal of Insect Conservation, vol. 2, no. 3-4, pp. 247-252, 1998. Hindawi Publishing Corporation Psyche Volume 201 1, Article ID 748635, 7 pages doi: 10. 11 55/20 11/748635 Research Article Relationships between Plant Diversity and Grasshopper Diversity and Abundance in the Little Missouri National Grassland David H. Branson USDA- Agricultural Research Service, Northern Plains Agricultural Research Laboratory, Sidney, MT 59270, USA Correspondence should be addressed to David H. Branson, dave.branson@ars.usda.gov Received 31 May 2010; Revised 25 September 2010; Accepted 5 November 2010 Academic Editor: Michael Sergeev Copyright © 2011 David H. Branson. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. A continuing challenge in orthopteran ecology is to understand what determines grasshopper species diversity at a given site. In this study, the objective was to determine if variation in grasshopper abundance and diversity between 23 sites in western North Dakota (USA) could be explained by variation in plant species richness and diversity. In this system with relatively low plant diversity, grasshopper species richness and abundance were not significantly associated with plant species richness in either year. Although a number of significant associations between plant diversity and grasshopper diversity were found through regression analyses, results differed greatly between years indicating that plant species richness and diversity did not lead to strong effects on grasshopper diversity metrics. Plant species richness appears to be too coarse grained to lead to accurate predictions of grasshopper species richness in this system dominated by generalist grasshopper species. 1. Introduction Grassland insect diversity is often linked to plant species composition and habitat structure [1-4]. Several general hypotheses have been proposed to explain relationships between plant and herbivore species richness [5, 6], with insect herbivore diversity often thought to generally increase with increased plant species richness due to increased resource diversity [3, 5]. Although habitat associations with grasshoppers have been studied since the early 1900s [7], it remains a continuing challenge in grasshopper ecology to understand patterns of species diversity [4, 8]. Numer- ous factors could influence grasshopper species diversity including resource availability, habitat structure, escape space, and predators [4, 9, 10]. Furthermore, management practices such as livestock grazing and fire impact plant species composition and subsequently affect grasshopper species composition [4, 11]. Many studies have examined relationships between grasshopper community composition and vegetation patterns in grassland ecosystems worldwide (e.g., [2, 4, 8, 12-14]). Plant diversity often positively affects grasshopper species diversity, but relationships are not consistent. Additionally, grasshopper feeding patterns can have important impacts on local plant abundance and community structure [15-17]. In most grassland ecosystems the nature of relationships between plant species richness and grasshopper abundance and diversity remains unclear [3, 4]. Grasshoppers are often the dominant native herbivore in grassland ecosystems worldwide, with widespread economi- cally damaging grasshopper outbreaks occurring frequently in western North America [11, 15]. Despite the economic importance of grasshoppers in the area of this study, the northern Great Plains [18, 19], relationships between plant diversity and grasshopper diversity and abundance are not clearly defined. In contrast to the majority of herbivorous insects, most grasshopper species tend to be generalist feeders that consume a variety of unrelated plant species [20, 21], As a result, relationships between plant species richness and grasshopper species richness could be weaker in grass dominated ecosystems with numerous grass or mixed feeding generalist grasshoppers. The objective of this study was to determine if variation in grasshopper abundance and diversity between 23 sites in western North Dakota (US) could be explained by variation in plant species richness and diversity. 2 Psyche Table 1: Characteristics of each site in western North Dakota. Site Elevation (m) Coordinates Plant 2001 species 2002 Grasshopper species 2001 2002 Charbonneau 689 47°46'33N 103°49'30W 11 6 19 19 Cheney 603 47°44'29N 104°01'35W 5 8 * 16 Devitt 600 47°38'37N 104°01'53W 12 7 18 14 East 7f0 47°36'35N 103°56'09W 8 7 13 18 Plant 609 47°38'05N 104°0T08W 8 5 17 16 Jacobson5A 690 47°48'04 N 103°48'31 W 6 5 19 24 Klandl 667 47°38'27 N 103°57'24W 5 6 19 27 IndergardN 675 47°35'14 N 103°49'39 W 8 7 15 13 IndergardS 730 47°34'43N 103°50'46W 7 6 23 22 Rau 757 47°42'08N 103°57'15W 11 9 14 20 Saltwell 751 47°36'32N 103°56'05W 5 8 15 24 SDlOf 700 47°33'23N 104°00'21W 8 5 17 18 101 Creek 654 47°33'44N 104°00'30W 9 8 11 18 SM02 686 47°39'28N 103°51'18W 5 4 19 20 SM05B 740 47°37'42N 103°45'45W 10 7 20 21 SM05NB 747 47°37'03N 103°45'58W 10 8 21 20 SM07B 655 47°36'54N 103°48'54W 8 9 13 19 SM11 708 47°43'37 N 103°52'24W 8 9 21 20 SM12 719 47°43'55N 103°50'46W 7 5 13 19 SM13 704 47°43'11N 103°49'05W 7 9 17 18 Shadwell 717 47°26'03N 104°02'30W 8 5 18 19 Whited 703 47°28'36 N 104°04'21W 8 7 15 16 Windmill 658 47°39'07 N 104°00'11 W 3 4 15 20 2. Materials and Methods The study was conducted on the Little Missouri National Grasslands in western North Dakota (USA), managed as part of the United States Forest Service Dakota Prairie Grasslands. The area of the study is characterized by wide summits and networks of gullies [22]. The historic plant community is a mixed grass prairie dominated by grasses including western wheatgrass ( Pascopyrum smithii ), blue gramma ( Bouteloua gracilis ), needle and thread ( Hesperostipa comata ), and green needlegrass ( Nassella viridula). The region is semiarid and receives approximately 355 mm to 400 mm of precipitation annually; most of which occurs during the growing season. Mean daily temperatures range from -17.2°C in winter to 29.4° C in summer. Precipitation measured at a nearby weather station during the growing season of 2001 was slightly above, while precipitation during 2002 was slightly below the long-term average. During the spring and early summer of 2001, 23 sites were established in the Little Missouri National Grassland. The sites were located within 35 km of each other, ranged in elevation from 600 to 751 m, and were randomly chosen to include a range of grassland habitat types (Table 1). Nearly all sites were dominated by native vegetation. At each site, a 10 m by 10 m subplot was established for sampling vegetation species composition and grasshopper densities. Grasshopper population densities were determined by counting the number of grasshoppers that flushed from within 20, 0.1 m 2 aluminum wire rings, following the methods of Onsager and Henry [23]. Rings were arranged in a grid of four rows, with 5 rings per row, and held in place by landscape staples. Sites were sampled for grasshopper population densities and species composition four times in 2001 and six times in 2002, between the last week of June and the first week of September. Sampling took place when air temperature was greater than 23° C. A sweep net sample was taken, using an insect aerial net with a four foot handle, in the vegetation surrounding the 10 m by 10 m sampling plot to establish grasshopper community composition. Vegetation structure was dominated by grasses and forbs, with few shrubs. An equal number of 150 sweeps were taken while walking slowly that rubbed on the soil surface and that passed through the vegetation canopy while walking rapidly [24]. Sweep net samples were frozen, and grasshoppers were later identified to species in the laboratory. To adjust for differences in sweep net sample sizes between sites, individual species densities were estimated by combining the percentage composition in sweep samples with grasshopper densities from ring counts. Vegetation species composition was examined in early July 2001 and 2002. Each side of the sampling site served as a 10 m transect with a fifth transect in the middle of the plot, with 500 sampling points per site. Along each transect, every one meter a standard 10-pin frame was used to determine vegetation composition based on the total number of contacts by a pin. A contact was considered as the pin point coming into contact with the basal area of a Psyche 3 plant, bare ground, or litter. Across both years of sampling, western wheatgrass was a dominant or codominant grass at 14 sites, blue grama at 13 sites, junegrass at eight sites, threadleaf sedge at three sites, needle and thread at two sites, crested wheatgrass (. Agropyron cristatum ) at two sites, green needlegrass at one site, and Kentucky bluegrass ( Poa pratensis ) at one site. For each site, total plant species richness, proportional coverage of live vegetation, and plant diversity were calculated. Relationships between insect species diversity and plant diversity could differ seasonally but were not assessed in this study. As grasshopper sample sizes were low in some sweep net samples from sites with low population densities, all sweep samples were pooled prior to analysis to reduce error [24], increase the probability that rare grasshopper species would be incorporated [5], and better account for varying grasshopper phenologies [2], Grasshopper abundance data was also averaged across sample periods within a year to reduce the influence of random sampling variation when few individuals are detected in density subsamples [25]. Data was transformed as needed. The majority of grasshopper species present at the sites overwinter as eggs and hatch in late spring or early summer; however four nymph- overwintering grasshopper species that hatch in late summer and become adults in the spring were caught in sweep samples. Only egg-overwintering grasshopper species were included in the analysis, as plant-grasshopper relationships would be expected to differ due to the divergent phenologies of these two groups. Patterns of grasshopper species diversity were examined using numerical species richness, Shannon index of species diversity, and Simpson evenness index [26]. Regression analyses were conducted to examine habitat vari- ables responsible for grasshopper abundance and diversity. Systat 12 (Systat Software Inc.) was used for all analyses. 3. Results and Discussion Cumulative plant species richness was relatively low, with a total of 31 species detected across all sites. Mean plant species richness was 7.24, with a maximum species richness of 12 species at a site (Table 1). Forb species richness ranged from zero to six species, while grass species richness ranged from two to seven. Vegetation was dominated by grass and sedge species, as is typical in this northern mixed grass prairie [22, 27, 28]. An average of ~88% of live vegetation hits were grasses and sedges. Abundant grasses and sedges were blue grama ( Buteloua gracilis), western wheatgrass (. Agropyron smithii ), junegrass ( Koeleria macrantha ), and threadleaf sedge ( Carex filifolia). The most abundant forb was the relatively ephemeral exotic common dandelion ( Taraxacum officinale), which is frequently present in native dominated grasslands throughout the United States. Fringed sage ( Artemisia frigida), scarlet globemallow ( Sphaeralcea coccinea), and phlox ( Phlox spp.) were other relatively common forbs. Egg- overwintering grasshopper species richness ranged from 11 to 27 across sampling sites in a given year, with a mean species richness of 18 (Table 1). A total of Table 2: Egg- overwintering grasshopper samples in 2001 and 2002. species caught in sweep Species 2001 2002 Ageneotettix deorum 1,553 2,374 Melanoplus sanguinipes 1,162 1,631 Phoetaliotes nebrascensis 863 1,084 Opeia obscura 575 668 Encoptolophus costalis 490 590 Philbostroma quadrimaculatum 487 720 Melanoplus gladstoni 411 314 Melanoplus femurrubrum 343 490 Melanoplus infantilis 273 387 Orphulella speciosa 206 277 Trachyrhachys kiowa 165 281 Amphitornus coloradus 140 185 Melanoplus dawsoni 128 350 Aulocara femoratum 126 176 Hypochlora alba 115 152 Melanoplus packardii 111 185 Melanoplus keeleri 109 205 Aeropedellus clavatus 92 197 Spharagemon equale 36 64 Arphia pseudonietana 33 68 Aulocara ellioti 31 64 Melanoplus confusus 24 39 Mermiria bivittata 16 19 Hadrotettix trifasciatus 16 24 Melanoplus bivittatus 14 51 Hesperotettix viridis 12 17 Melanoplus differentialis 10 0 Dissosteira Carolina 8 2 Metator pardalinus 7 36 Dactylotum bicolor 1 1 Total caught 9,236 13,590 34 egg-overwintering grasshopper species were collected (Table 2). Mean grasshopper species richness per site was slightly higher than Kemp [29] and foern [4], while total species richness was within the range observed in other similar studies in the western US (e.g., [4, 29-31]). Average grasshopper density across sites was 7.4 per m 2 , with a low of 1.9 and a maximum of 20.8 per m 2 at a given site. Relative to long-term grasshopper densities in the area, the densities were not exceptionally high, just prior to this study, grasshopper densities were documented at 40 and 130 per square meter [18, 19]. Flowever, grasshopper densities were much lower during a five-year period immediately following this study [17]. Common grasshopper species are presented in Table 2. Plant diversity did not affect grasshopper abundance (Table 3), similar to the findings of joern [10] in tallgrass prairie. There was no effect of plant species richness on grasshopper species richness in either year (Figure 1, Table 3). Although several significant associations were 4 Psyche Table 3: Results from regression analyses of plant species richness, live cover percentage, Shannon diversity, and Simpson evenness on grasshopper abundance and diversity. Regression equations are provided for results with a P value less than .1. Independent (plant) Dependent (grasshopper) Statistical data A. 2001 Species richness R 2 = 0.002, P = .84 Species richness Shannon diversity 7 = 1.70 + 0.055X; R 2 = 0. 17, P = .057 Simpson evenness Y = 0.215 + 0.024 X,R 2 = 0.19,P = .045 Abundance 7 = 8.6 - 0.32X; R 2 = 0.02, P = .5 Species richness R 2 < 0.001, P = .99 Shannon diversity Shannon diversity R 2 = 0.1, P = .16 Simpson evenness R 2 = 0.06, P = .26 Abundance R 2 = 0.03, P = .43 Species richness Y = 8.23 + 0.292X; R 2 = 0.4; P = .001 Live cover Shannon diversity R 2 = 0.1, P = .15 Simpson evenness R 2 = 0.016, P = .6 Abundance 7 = -3.37 + 0.329X; R 2 = 0.2, P = .036 Species richness R 2 = 0.003, P = .8 Evenness Shannon diversity R 2 = 0.11, P = .12 Simpson evenness R 2 = 0.05, P = .33 Abundance R 2 = 0.024, P = .5 B. 2002 Species richness R 2 = 0.01, P = .6 Species richness Shannon diversity R 2 = 0.08, P = . 2 Simpson evenness R 2 = 0.09, P = .15 Abundance R 2 = 0.06, P = .25 Species richness Y = 24.01 - 3.882X, R 2 = 0.19, P = .04 Shannon diversity Shannon diversity R 2 = 0.05, P = .32 Simpson evenness Y = 0.168 + 157X, R 2 = 0.21, P = .03 Abundance Y = 15.0 - 6.96X, R 2 = 0.24, P = .015 Species richness R 2 = 0.02, P = .53 Live cover Shannon diversity Y = 1.8 + 0.014X, R 2 = 0.2, P = .03 Simpson evenness Y = 0.158 + 0.008X, R 2 = 0.212, P = .027 Abundance R 2 = 0.003, P = .8 Species richness Y = 15.4 - 9.6X, R 2 = 0.25, P = .016 Evenness Shannon diversity R 2 = 0.035, P = .39 Simpson Evenness Y = 0. 151 + 0.348X, R 2 = 0.22, P = .025 Abundance 7 = 15.7 - 15.36X, R 2 = 0.26, P = .014 found through the regression analyses, results differed greatly between years (Figure 1, Table 3). Grasshopper community Shannon diversity and Simpson evenness were positively associated with plant species richness in 2001, indicating that sites with increased plant diversity had a more evenly distributed grasshopper community assemblage. By contrast, grasshopper species richness, evenness, and abundance were all positively associated with Shannon diversity of plants in 2002. Grasshopper species richness and abundance were positively associated with the percentage of live plant cover in 2001, while diversity and evenness of the grasshopper community were positively associated with live cover in 2002. Grasshopper species richness, evenness, and abundance were all positively associated with plant species evenness in 2002. As significant relationships differed almost entirely between years, it appears unlikely that either plant species richness or diversity was a strong causative factor responsible for observed significant statistical results. However, a consistent result in both years was that grasshopper species richness was not positively associated with plant species richness (Figure 1). Although specialist grasshopper richness would be expected to increase with plant species richness, this is a highly grass dominated system with many generalist feeding grasshoppers [32]. Strong conclusions regarding the nature of the relation- ship between plant species diversity and grasshopper species Psyche 5 O 2001 O 2001 X 2002 X 2002 (a) (b) Figure 1: Relationship in 2001 and 2002 between (a) species richness of grasshoppers and plants and (b) Shannon diversity of grasshoppers and plants. diversity in North America remain difficult. In a study across an elevational gradient in Montana, Wachter et al. [13] found no significant relationships between plant cover or species richness and grasshopper species richness, diversity, and abundance. By contrast, Fielding and Brusven [14] found a positive correlation between plant and grasshopper species richness in semiarid rangeland. In a more productive tallgrass prairie system, Evans [12] and Joern [4] also found grasshopper species richness was positively related with plant species richness. Plant species richness was similar in the study by Joern [4] and higher in the study by Fielding and Brusven [14]. In this study, as well as in Joern [4] and Fielding and Brusven [14] where positive relationships were found between grasshopper and plant species richness, the ratio of grasshopper species to plant species was typically greater than 1.0. In a desert environment in the southwestern US with low grasshopper species diversity but several spe- cialist species, Otte [9] found a positive relationship between grasshopper and plant species diversity when the ratio of grasshopper species to plant species was always less than 0.43. As a result, the lack of a relationship between plant and grasshopper species richness does not appear a result of grasshopper or plant species richness varying by orders of magnitude from other studies. As pointed out by Fielding and Brusven [14], “grasshopper species richness is probably not a simple function of plant species richness.” Grasshopper populations are highly cyclical in this area and respond to weather conditions [18, 19, 27]. Drought has been shown to reduce grasshopper species diversity at nearby sites in eastern Montana [33], while a late summer rainfall event led to a three-fold increase in grasshopper densities in the following year [19]. Precipitation patterns during 2001 and 2002 were not extreme outliers relative to long- term averages. Given the variation in correlations between years, longer-term sampling would be required to determine if consistent patterns emerge and if patterns vary with precipitation or densities. Grasshoppers were relatively abun- dant during the period of the study and density dependent factors could have influenced grasshopper or plant species composition. Both intraspecific and intraspecific exploitative competition can play an important role in grasshopper population dynamics and plant composition [19, 34, 35]. In addition, preferential grasshopper herbivory has been shown to influence plant species diversity in study area when abundant [17]. Although grasshopper herbivory could have removed all visible plant material prior to plant sampling, vegetation sampling occurred relatively early in the summer. Many of the hypotheses proposed to explain positive relationships between plant and herbivorous insect diversity are based on the fact that many insects are relatively special- ized [5]. However, many grasshopper species are generalists [17, 32]. As a result, inconsistent and weak relationships could be reflective of the ability of generalist grasshoppers to feed on numerous plant species or could be an artifact of difficulties in sampling rare species [5]. Haddad et al. [5] conducted an 11-year experiment manipulating plant diversity and examining effects on arthropod herbivores and predators and found herbivore arthropod species richness was strongly positively related to plant species richness only when examining cumulative species richness across the 6 Psyche 1 1 year time period. This illustrates the potential importance of longer term sampling when examining relationships between plant and grasshopper species richness. The results from this study also support Kemp et al. [36], who argued that plant species richness is too coarse grained a measure to lead to accurate predictions of grasshopper species richness. Although plant community associations are likely to be a better predictor of grasshopper species richness than plant species richness in a variety of ecosystems [36, 37] , a potential constraint is that ordination techniques may result in system specific conclusions regarding relationships between plant communities and grasshopper species. Acknowledgments The author thanks Nicole Davidson for assistance in data organization and Donovan Craig for setting up sampling sites and collecting data. References [1] E. W. Evans, “Fire as a natural disturbance to grasshopper assemblages of tallgrass prairie,” Oikos , vol. 43, no. 1, pp. 9- 16, 1984. [2] W. P. Kemp, S. J. Harvey, and K. M. O’Neill, “Patterns of vegetation and grasshopper community composition,” Oecologia, vol. 83, no. 3, pp. 299-308, 1990. [3] N. M. Haddad, D. Tilman, J. Haarstad, M. Ritchie, and J. M. H. 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V. Sykora, and C. J. F. Ter Braak, “Arthropod assemblages are best predicted by plant species composition,” Ecology, vol. 89, no. 3, pp. 782-794, 2008. Hindawi Publishing Corporation Psyche Volume 2011, Article ID 501983, 9 pages doi: 10. 11 55/20 11/50 1983 Research Article The Ontology of Biological Groups: Do Grasshoppers Form Assemblages, Communities, Guilds, Populations, or Something Else? Jeffrey A. Lockwood Department of Philosophy, University of Wyoming, Department 3392, 1000 E. University Avenue, Laramie, WY 82071, USA Correspondence should be addressed to Jeffrey A. Lockwood, lockwood@uwyo.edu Received 5 August 2010; Accepted 11 November 2010 Academic Editor: Alexandre Latchininsky Copyright © 2011 Jeffrey A. Lockwood. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Acridologists have used a variety of terms to describe groups of grasshoppers, including assemblage, community, guild, and population. This terminological diversity has raised the question of whether one of these descriptors is the correct one. I take the position that these terms pick out different features of the natural world such that there is no unconditionally or uniquely correct term. By adopting the framework of constrained perspectivism — a form of philosophical pragmatism — it is argued that a term is correct if it accurately reflects the conceptual framework of the investigator and effectively communicates this perspective to others. Such an approach gives rise to terminological pluralism that avoids the problems of relativism (the subjectivist’s view that any term can be used) and absolutism (the objectivist’s view that there is a single correct term). I describe the contexts in which the most common terms are appropriate. 1. Introduction: The Problem Acridologists have used various terms to describe the groups of grasshoppers that are the focus of their work. The terms most often used are assemblage, community, guild, and population. Using the Google Scholar [1 ] to analyze how fre- quently scientists have used these terms revealed that of 1,459 hits: “grasshopper assemblage” appeared 65 times (4%), “grasshopper community” 413 times (28%), “grasshopper guild” 1 time (<1%), and “grasshopper population” 980 times (67%). One might respond to the assortment of terms by assert- ing that such variety does not imply a problem or confusion. In fact, this view was expressed by three reviewers of this paper. These scientists tacitly agreed that the ecological terms were well defined (we will see that this is demonstrably not the case in the discussion of “population” and to some extent with “community” and “guild”) or at least there was no confusion among acridologists. But their explications revealed a conceptual morass with various contradictions. The first reviewer maintained that “the only issue is the occasional sloppy individual who calls a grasshopper assemblage a community.” For this scientist, there is a single, correct term for groups of grasshoppers, which is “assemblage” (for the moment, let us set aside the fact that the supposedly sloppy use of “community” occurs far more often than the putatively correct term of “assemblage” — and “population” is more commonly used than either of these). By this account, all right-thinking acridologists know that groups of grasshoppers are called “assemblages,” so the case is closed. In an ironic twist, the second reviewer contended that all the terms have “tight and accepted usages,” such that there is simply no confusion among acridologists. For this scientist, there are four standard terms that are variously and correctly used to describe groups of grasshoppers. But both reviewers cannot be correct. Either the first acridologist is in error (not all groups are “assemblages”) or the second reviewer is mistaken (terms other than “assemblage” are conceptual errors). 2 Psyche The situation becomes no clearer with the assertion of the third reviewer that, “the choice of terms by researchers seems relatively uninformative/unimportant as some researchers may rather arbitrarily choose a term.” In other words, this scientist agreed with the first in that some researchers were sloppy, but s/he seemed quite uncommitted to the notion that all groups are properly called “assemblages.” And this reviewer also contradicted the second in suggesting that the chosen term is uninformative. The resolution, according to the third reviewer, is that the word choice is unimportant: “what matters is the context of how those words are used in a journal article.” This represents a wholly inefficient approach to terminology — rather like referring to locusts in a title or abstract, only to have the reader discover that the paper is about grasshoppers — and it presumes that scientists take the time to read entire articles. Oftentimes and justifiably, researchers use titles to find the literature on a particular kind of grouping (e.g., community), and if others use an arbitrary term (e.g., assemblage or population) as a label, then important work will be overlooked and irrelevant publications will be sought. At this point, all we can safely assert is that at least some acridologists — including apparently three highly qualified and experienced practitioners — are collectively confused by the terminology applied to groups of grasshoppers. Based on my experience, many graduate students and junior scientists working in this field are also somewhat bewildered by which term should be used to describe a group of grasshoppers in a habitat. So, it would appear that the editors of this special issue of Psyche were on to something in identifying one of the topics of interest as “Grasshopper species in a habitat: a community or an assemblage?” One solution is to simply presume that the correct term is that which is used by the majority of scientists. If so, then a group of grasshoppers should be called a population (not “community” or “assemblage”, as proposed by the editors). However, this seems entirely too quick of a solution to the terminological problem. It is certainly possible that most workers are misusing or misunderstanding a term. Moreover, we cannot summarily conclude that all of the scientists describing grasshopper groups are necessarily referring to one and the same thing. To clearly frame the problem — along with possible solutions and their shortcomings — it is helpful to consider four possibilities. 1.1. The Terms for Grasshopper Groups Are Synonyms. The various terms might be synonyms, much as one might refer to “short-horned grasshoppers” in one paper and to “acridids” in another, or to “nymphs” in one place and “hoppers” in another. If so, the inconsistencies are not substantive at all. However, the problem with the different expressions for groups of grasshoppers seems more than a matter of alternative words for the same entity. Ecologists form different impressions from the various terms used by acridologists; a “population” picks out something in nature that is not the same thing as a “community” [2]. Hence, the possibility of substantive errors and misunderstandings is real. 1.2. The Terms for Grasshopper Groups Are Subjective Constructs. The various terms may simply reflect human artifice. The manner in which grasshoppers are grouped could be an entirely subjective matter, such that there is no basis to argue for one formulation over another. A nominalist (i.e., one who holds that beyond the reality of individual entities, all higher groupings are human inventions) might contend that while individual grasshoppers actually exist, any amalgamation of these individuals represents a cultural construct — a sort of potentially useful fiction [3]. As such, one could be a realist about single grasshoppers but an antirealist about groups of grasshoppers [4]. Taken to an extreme, one could just as defensibly combine grasshoppers based on the potential they have as fish bait, the third letter of their scientific name, or the color of their tibia as one might group them in terms of competitive interactions, behavioral tendencies, or taxonomic relations. But such a strong nomi- nalist view strikes us as rather implausible. Certain groupings of grasshoppers seem to reflect nonarbitrary qualities of the organisms (e.g., those that eat only grasses) much more so others (e.g., those that happen to be airborne at a given moment). 1.3. The Terms for Grasshopper Groups Are Objective Truths. There could be an objective fact of the matter as to which term uniquely picks out a real thing in the world [5] . A realist might argue that groups of grasshoppers are actual, mind- independent entities and that these possess some unifying property that makes it correct to call them communities but not populations, for example. Perhaps groups of grasshop- pers are like deer herds, wherein the individuals have interactions or relationships which form a distinct entity. However, a strong realist position seems difficult to defend. It is not unambiguously evident what relationship among the grasshoppers makes the collective into an actual, objectively existing whole. At least there does not appear to be a single candidate for such a relationship, as the interactions might be understood in various terms (e.g., mutualism with regard to predator swamping or competition in terms of food acquisition). And this leads us to the fourth and most viable possibility. 1.4. The Terms for Grasshopper Groups Are Interactional Per- spectives. The terms used to describe groups of grasshoppers could reflect neither purely subjective nor objective criteria. There may be multiple, biologically compelling ways of identifying groups although it will also be the case that some approaches are absurd. For the pluralist [6, 7], there is more than one way of being right (contrary to the objective absolutist), but it is still possible to be wrong (contrary to the committed subjectivist). As such, the groupings of grasshoppers are interactional [8], being “made” — rather than subjectively created or objectively discovered — through the interests of the scientist interacting with the rich (but not unlimited) possibilities of the real world. That is to say, reality can be divided in many ways, but not just any way. Thus, the researcher has a particular perspective with respect to Psyche 3 a line of inquiry and thereby picks out one of the biologically plausible ways to group grasshoppers. Such an approach to understanding some biological groups has been advanced — at least implicitly — by ecol- ogists. In his analysis of the concept of communities, Underwood [9] described the subjectivist and objectivist views. The former position is that “communities are simply a human invention. . .used to describe the collection of organisms that are found in the same place at the same time,” and the latter view is that communities are “valid and necessary object [s] of study” which are held together through biological interactions. Underwood [9] observed that these two perspectives have been alternately in favor and that “the reality is probably somewhere in between” although he does not specify an intermediate view. However, his contention that no definition will satisfy all — or even most — ecologists, opens the door to the possibility of a pluralistic approach. 2. Analogous Cases and Their Implications for Grasshopper Groups 2.1. Perspectival Approaches to Individual Entities. Is an axe a weapon or a tool? The group of implements to which an axe belongs does not seem to be objectively (or at least singularly) determinable. The right assignment of the axe depends on how it is used. In the hands of Lizzie Borden (who according to legend and the childrens ditty “took an axe and gave her mother forty whacks”), the thing should be considered a weapon, but in the hands of Paul Bunyan (the mythic lumberjack), it is a tool. Nor is the correct term for the axe merely a philosophical puzzle — the consequences of being wrong could be serious. The problem of how to perceive an axe persists even when the instrument is not in the hands of others. That is, my own intentions or interests are critical to what category of things the axe belongs to when I reach for the instrument. The “axe problem” reveals an important aspect of how we categorize objects. The subjective perspective of the individual engaging the objective entity is critical to our understanding. Scientific perspectivism [10] is the view that the ontology (what is real) and metaphysics (the properties of real things/processes) are both constrained by the facts (e.g., the axe is a heavy, sharp object so it is nonsensical to use it as a pillow) and open to an array of possible interests (e.g., weapon, tool, doorstop, etc.). The pluralism that arises from this understanding underwrites a philosophy of ecology that is called constrained perspectivism [11]. Starting with the categorization of an axe creates an accessible starting point, but groups of entities (e.g., grasshoppers) are not necessarily single things. We might contend that an axe is not a single item but is composed of a handle and a head, but these parts seem to be so intimately related in terms of the function of the whole that treating an axe as a particular item is appropriate. In fact, that is the matter we are trying to resolve: are groups of grasshoppers real things (ontology) and what sorts of things are they (metaphysics)? 2.2. Perspectival Approaches to Collective Entities. Imagine that a person walks into a room containing old furniture. The individual wants to describe what he sees and wonders about the correct term to use for the group of chairs, tables, lamps, and whatnot. The challenge is whether there is a single, right way to convey to others what he has observed — is there an objective descriptor? It seems not, as the most accurate term will depend on his interests and those of the persons with whom he will be communicating. If the man is a furniture dealer, he may tell his assistant that he has come across an “inventory of antiques.” However, if he is a historian and recognizes that the furniture is a matched set from a single room of Louis XIV, the grouping might be termed a “17th century salon.” But if the fellow is an artist, he might see the placement and spacing of the furniture as aesthetically pleasing and refer to the items as a “balanced arrangement of three-dimension forms.” And finally, if the man is a millionaire, he might perceive the furniture as a “collection of status-enhancing objects.” The point here is that there appears to be no uniquely right term for the assembled items. The interests of the observer and those with whom he is speaking are inextricably woven into choosing the right description. This is not to say that there is no way to be wrong about a term for the furniture. In fact, there are at least two mistakes to be made. First, the man could simply use a term that does not pertain to groupings of furniture. For example, the millionaire could tell his interior decorator that he found a “squadron of furniture” or the antique dealer could tell his assistant to prepare the shop for a “herd of chairs and tables”. Neither description is meaningful or appropriate for items of furniture — there is a category error in using such terms. Second, the man could use a term that is uninformative or even misleading to the listener. If the artist tells his impoverished bohemian friend that he should go to see the “collection of status-enhancing objects,” the other fellow would likely be confused — or at least not understand why he ought to be interested. Or if the historian submits a paper to the Journal of French History reporting that he came across a “balanced arrangement of three-dimensional forms,” then he has failed to tell his colleagues what is important about his observation. 2.3. Perspectival Approaches to Scientific Referents. Before we consider the importance of terminology for groups of grasshoppers, it is useful to briefly consider two analogous cases in science and why the use of alternative terms mattered. In physics, there has been considerable debate as to the nature of light [12, 13]. Following Newton, most scientists accepted some version of the “corpuscular hypothesis” in which light was taken to be composed of particles. In the 18th century, Leonhard Euler advocated a wave theory of light (Newton also contended that “aetheric waves” played a role, although this was largely ignored). Both the particle and wave advocates were able to construct sound arguments and compelling experiments in defense of their views. Thomas Young’s famous double-slit experiment set the stage for our 4 Psyche contemporary understanding that light is both wave and particle — and how one perceives its nature depends on the choice of instrument or, in effect, one’s interests. It matters a great deal in physics whether something is a wave or a particle, but at least with respect to light there is no objective fact of the matter. In ecology, one’s interests are critical to the interpretation of an organism’s role in a habitat. Consider the case of Echium plantagineum in Australia [14]. For those with an interest in producing high-grade honey or ruminant livestock feed in drought stricken regions, the plant is a beneficial component of the ecosystem and warrants the common name “Salvation fane”. But for those who have an interest in restoring native habitats or producing quality forage on disturbed pastures, the plant deserves the moniker “Patterson’s Curse”. Whether this plant is a beneficial or pest species matters a great deal — and the right classification or term depends on one’s interests. So, is there a correct term for a group of grasshoppers? The American pragmatist William fames [15] argued that: the human mind is essentially partial. It can be efficient at all only by picking out what to attend to, and ignoring everything else, — by narrowing its point of view. Otherwise, what little strength it has is dispersed, and it loses its way altogether. Man always wants his curiosity gratified for a particular purpose. This position would suggest that the acridologist must choose a perspective, that there is some particular interest being served by an investigation. Terminology is thus pragmatic (reflective of interests), perspectival (based on where one stands conceptually), and pluralistic (dependent on more than a single, correct, or objective viewpoint). So there is a right term to use for a given situation — whatever most accurately conveys the intentions of the researcher and communicates this point of view to fellow scientists. 3. The Right Term for a Group of Grasshoppers: Conceptual Context If the pragmatic philosophy of constrained perspectivism with its pluralist solution is to be adopted by acridologists, there are three concepts to keep in mind as we consider the various terms that might be used to describe groups of grasshoppers. 3.1. Role of Objectivity. The acridologist faced with multiple terms for groups of grasshoppers might worry that the pluralist approach is a slippery slope. Can objectivity check the slide toward radical subjectivism? I will have more to say about this later, but for the present it is sufficient to maintain that objectivity can limit pluralism in two ways. First, constrained perspectivists take it to be the case that there is a mind-independent world “out there”, and reality constrains the ways in which we can productively frame our understanding [ 1 1 ] . In short, the world “pushes back” when we form beliefs that lead to actions which do not accord with external reality. If we think of a group of grasshoppers as a terrorist cell and launch a full-scale military attack to destroy them, the world pushes back through the economic costs, political repercussions, environmental damage, and social condemnation of our foolishness. Second, objectivity is an important “regulative ideal” — an unattainable goal which we can rationally adopt so as to orient our pursuits (not unlike global peace or eco- nomic justice). But our understanding is invariably domain- specific. As Reiners and Lockwood [11] maintained, “We can rise above individual bias, but we cannot ascend to a God’s eye view such that truth is no longer relative to a particular conceptual system.” So, we must be keenly aware of our chosen perspective and then aspire to unbiased understanding within this framework. One might even say that we should try to be as objective as possible about and within our subjective context. 3.2. Nature of Groups. In some biological settings, groups are readily observable. The group of cells comprising an organism is quite evident, and even some ecological groups are discernible (e.g., a herd of deer, a school of fish, a swarm of locusts). Flowever, most groups of grasshoppers that are studied by ecologists are not visible. This is not a challenge particular to acridology. Indeed, Reiners and Lockwood [11] made the case that: [M] any ecological entities are not perceived (i.e., seen by our eyes or instruments), but conceived. . .ecology is particularly prone to ontological and metaphysical problems such that we are concerned with how to carve up the world into entities and processes that are often unobservable (has anyone actually seen species, speciation, communities, metabolism, ecosystems, or equilibrium?). For the most part there are not directly observable properties of a group of grasshoppers that provide a kind of objective taxonomy. That said, we may be able to infer qualities of the collective via sampling (e.g., density and species composition). Furthermore, various instruments and measurements have been developed to discern the effects of the group (e.g., forage loss and nitrogen levels). 3.3. Practical Relevance. In the context of pragmatism, James [15] maintained that “There can be no difference anywhere that does not make a difference elsewhere.” That is to say, a distinction between “population” and “community”, for example, is vacuous if there is no actual consequence of calling a group by one or the other of these names. Perhaps this is why there seem to be few arguments about whether acridologists should refer to “nymphs” or “hoppers”; the distinction makes no difference in terms of our beliefs and actions. As will be evident in the following section, the terms which we apply to groups of grasshoppers may well make a difference with regard to orienting the research agenda of science, communicating our findings, and perhaps even developing sound government policies and taking effective management actions. These potential consequences should not be surprising in light of other cases in which how Psyche 5 scientists have chosen terms and perspectives mattered (see Perspectival approaches to scientific referents ). 3.4. Principled Relevance. Assuming that the reader is not entirely on board with the framework of pragmatism that is captured by constrained perspectivism [11], there is a principled reason why the choice of terms in science matters. That is, science is thought by many to be our closest approximation to the way the world actually is. Indeed, scientists generally favor the realist’s view that we are justified in taking the referents of science to correspond with objective reality. If so, then the matter of what ecologists call groups of organisms is not an artificial controversy. Rather than making a philosophical mountain out of a scientific molehill, being clear and accurate in our language is vital to the practice of science. We would not countenance saying that 3.4 grasshoppers/m 2 was 4 grasshoppers/m 2 nor would we allow a colleague to refer to a katydid as a locust, so we should not be complacent about referring to a population as a community if, as I argue, we believe that these are essentially different entities. 4. The Right Term for a Group of Grasshoppers: Plausible Options The predominant terms used to describe groups of grasshop- pers are assemblage, population, community, and guild. Other terms for ecological groupings, such as association, inventory, and biocoenosis, can be subsumed under these more conventional descriptors. 4.1. Grasshopper Assemblage. An assemblage has the conno- tation of being a haphazard or accidental grouping of objects. This sense is reflected in the definitions used by ecologists. Allaby [2] provided the most fully elaborated account of the term: a collection of plants and/or animals characteristi- cally associated with a particular environment that can be used as an indicator of that environment (e.g., in geobotanical exploration). The term has a neutral connotation. Its use does not imply any specific rela- tionship between the component organisms, whereas terms such as “community” imply interactions. The idea that an assemblage is whatever organisms happen to be present was echoed in Lewis’ [16] more concise defi- nition: “A collection of co-occurring populations.” Although Underwood [9] did not explicitly define an assemblage, he used the term to describe collections of organisms that do not appear to form integrated units but simply reflect a shared physiological tolerance for a particular environment. Such a notion is clearly consonant with those of Allaby [2] and Lewis [16]. Lincoln et al. [17] provided a definition within the context of paleontology: “a group of fossils occurring together in the same stratigraphic level (an assemblage zone).” Even this definition is consistent with the “same place, same time” notion used by ecologists. Other authors of ecological and environmental references omit “assemblage” entirely [18-20], so one might presume that the term is somewhat limited in its use. However, Google Scholar [1] produced 1,100 hits for “bird assemblage” and 12,600 hits for “fish assemblage”, so the term is evidently common with regard to some organisms. Botanists use the term “association” for stable plant communities [ 17, 19] which are taken to have greater ecological coherence than assemblages of animals. If acridologists accept that a “grasshopper assemblage” is just whatever species happen to coexist in some habitat, then the term seems peculiar in light of scientific investigations. The neutrality of “assemblage” suggests that the scientist had no particular theoretical interest in the group of insects with respect to ecology or evolution. This would lead one to wonder why the individual bothered to amass data about a set of objects without some hypothesis having structured the research. Perhaps the most plausible response to this pertains to those works that are not hypothesis driven but represent descriptive natural histories. Pfadt’s Western Grasshoppers [21] is a fine example of this kind of conceptual neutrality. In addition to purely descriptive scientific works, there may be nonscientific reasons for knowing about the grasshoppers at a particular time and place. However, these other reasons are not neutral with respect to other human interests. Pest managers may not be acting within any conceptual ecological framework in making decisions about grasshop- pers. Along with a decision support system (e.g., [22]), simply knowing what species are present and at what densities may be all that is required for economically sound action. As such, a scientist who is emulating the perspective of a pest manager might well be justified in referring to a “grasshopper assemblage”; all of the individuals present (and thereby constituting a potential object of suppression) are being perceived as a group without regard to further ecological inquiry. As with pest managers, environmental managers of public lands, private reserves, and other habitats that support grasshoppers may be acting from the basis of agency standards, legislative mandates, or advisory board policies. Likewise, conservation objectives are grounded in a set of values external to ecological theory although they may be informed by scientific concepts. Just as the pest manager’s interest is economic, the environmental manager’s concern may be social, legal, or moral. In the context of environmental management, “assem- blage” would seem to be appropriate although there is also some use of “inventory” (this term generated 119 hits in Google but none in Google Scholar). This latter term seems to conceptually align with the metaphorical perspective of biodiversity conservation insofar as managers attend to the protection of a biological stockpile or warehouse. “Grasshopper inventory” was used by Walter et al. [23] in the context of conservation biology, and the term appears on the websites of the Konza Prairie Educational Program [24] and the Medford Oregon office of the Bureau of Land Management [25]. However, conservation biologists seem to more often refer to grasshopper assemblages; for example, “Responses of grasshopper assemblages to long-term grazing management in a semi-arid African savanna” [26] and 6 Psyche “Effects of fire disturbance on grasshopper (Orthoptera: Acrididae) assemblages of the Comanche National Grass- lands, Colorado” [27]. 4.2. Grasshopper Population. The most common term for a group of grasshoppers is “population”. In this regard, two questions are pertinent: is it legitimate to refer to a group of multiple species as a population, and what is the ecological interest/perspective that differentiates a population from an assemblage? Various references are inconsistent with regard to whether the definition of population applies to more than one species. Lewis [16] favored the single species notion of a population as “A collective group of individuals of the same species (or other taxa in which individuals exchange genetic information) occupying a particular space.” Likewise, Allaby [2] defined a population as “a group of organisms all of the same species, which occupies a particular area,” but he goes on to note that this term can also be used in a statistical context for “any group of like individuals” (which presumably could include more than one species). The dual possibility of single and multiple species was echoed by Lincoln et al. [17]. Explicit allowance that “population” can refer to a group composed of one or more species is found in Allaby ’s earlier reference in which he maintained that a population can be individuals within a species (“e.g., the human population of a particular country”) or a larger taxonomic group (“e.g., the bird population of a particular area”) [19]. This broader approach was endorsed by Martin and Hine [20], who defined a population as both, “A group of individuals of the same species within a community” and “The total number of individuals of a given species or other class of organisms in a defined area, e.g. the population of rodents in Britain.” So, it appears that acridologists are not misusing “population” when referring to a group comprised of more than a single species. The ecological perspective that is reflected in referring to a group as a population is evident in the definitions. Allaby [19] states that this term obtains when a group is “considered without regard to interrelationships among (the individuals),” and “when describing phenomena that affect the group as a whole (e.g., changes in numbers).” Hence, it is the dynamics of the group, its spatial distribu- tion, or temporal changes, that motivate the investigation of a population. Indeed, many references include entries pertaining to these qualities, such as “population biology”, “population density”, “population dynamics”, “population ecology”, and “population growth” [17-20, 28]. Thus, an acridologist seems to be justified in calling a group of grasshoppers a population if the purpose of the investigation is to understand the factors which explain the spatial patterns or (particularly) temporal dynamics of the organisms. As such, it seems quite appropriate to use this term in contexts such as: “A perspective of grasshopper population distribu- tion in Saskatchewan and interrelationship with weather” [29] and “A simulation model for testing the dynamics of a grasshopper population” [30]. 4.3. Grasshopper Community. Aside from “population”, the most common term for a group in acridology is “grasshopper community”. And once again, two questions are pertinent: is it legitimate to refer to a group comprised of only a single family as a community, and what is the ecological interest that differentiates a community from an assemblage or population? Although few terms in ecology generate full agreement with regard to definitions, there appears to be considerable consensus as to what makes a group of organisms a com- munity. In all of the references considered for this paper, the authors made clear that a community is comprised of different species [2, 16-20, 28]. However, there appears to be no indication that these species must include members of different higher taxa (i.e., multiple families, orders, classes, phyla, or kingdoms). Only Martin and Hine [20] refer to communities as including plants and animals, but they also note that “Larger communities can be divided into smaller communities,” which could presumably include a single taxonomic family. In fact, Google Scholar [1] searches for “bird community” and “fish community” both generated more than 10,000 hits. As such the term “grasshopper community” seems entirely appropriate with regard to its scope of taxonomic inclusion. This leaves the question of what qualities make a group of grasshoppers a community. There is also considerable agreement that for a group of organisms to constitute a community there must be interactions (e.g., trophic, mutualistic, and competitive relationships) among the individuals that provide struc- ture [2, 17, 20]. Even definitions that do not make the relational aspect explicit are suggestive of such a criterion. Both Parker’s [18] “distinctive combination of species” and Allaby ’s [19] “naturally occurring group of organisms that occupy a common environment” would seem to imply, if not require, that a relational factor unites the collective. The matter of there being valid grasshopper communities would seem to be settled except for the confusion that arises with an allied term. Underwood [9] opens the door with his description of early marine ecologists who had to dredge or otherwise grab samples in a haphazard fashion because they were unable to see into the habitat. The term used to describe the group of collected organisms was “biocoenosis”. This was evidently a nonnatural collection of species taken from a particular location at a given time. As such, one might suppose that this would have been an assemblage. However, the ecologists described these groups in terms of being equilibrial communities, so the interactions among the organisms served as the conceptual context. The result of this hybridization of assemblage and community was terminological confusion. While Parker [18], Lewis [16], and Lincoln et al. [17] equated “biocoenosis” with “community”, Allaby [19] explicitly defined a coenosis as “A random assemblage of organisms that have common ecological requirements, as distinct from a Community.” To make matters worse, Lincoln et al. [17] noted that biocoenosis is often used as an alternative term for “ecosystem”, and Allaby [2] equated it with “biome”. With regard to acridology, Google Scholar [1] revealed no citations with the term Psyche 7 Table 1: Terminology used for groups of grasshoppers and the perspectives in which these descriptors are most appropriate. Term Context Assemblage Inventory Population Community Biocoenosis Guild When there is primarily a nonecological interest in the economic or other values of the group, such as in pest management or conservation When there is primarily a nonecological interest in the group as a component of biodiversity, most often for the purposes of conservation When there is primarily an ecological interest in the spatiotemporal dynamics of the group and the factors that account for these quantitative changes When there is primarily an ecological interest in the interactions within the group (e.g., mutualism and competition) and how these structure membership Perhaps equivalent to “community,” but the ambiguity in use is such that the term is probably not a clear expression of a particular perspective When there is primarily an ecological interest in the role that the group plays in its use of a common resource, usually in a similar fashion “grasshopper biocoenosis,” although there was one reference to “grasshopper coenosis”. Given the ambiguity and rarity of (bio) coenosis to describe groups of grasshoppers and the most common view that the term is equivalent to “community”, it seems reason- able to suggest that the latter term be used. The appropriate context for the use of “grasshopper community” is when the scientist is interested in the ecological relationships among the individuals (e.g., competition for food or trophic inter- actions) and how these bind the collective into a coherent group. It should be noted that “grasshopper community” may include nongrasshopper species as communities are often named for the dominant, but not sole, taxon [17]. Examples of studies in which interactions are the perspective taken by the researcher include “Arid grassland grasshopper community structure: comparisons with neutral models” [31] and “The role of vertebrate and invertebrate predators in a grasshopper community” [32]. 4.4. Grasshopper Guild. The term “guild” is not often used to describe a group of grasshoppers. However, it is worth considering what sorts of features this concept picks out and the contexts in which it would be appropriately used (versus assemblage, population, or community). Although “guild” is not defined in several of the sources used in this analysis [18, 20, 28], those that include the term agree on its meaning: a group of (perhaps closely related) species which use an ecological resource, usually in a common fashion [16, 17, 19]. Like a community, a guild includes multiple species. But the distinguishing feature of the group is more specific than in the case of a community, where any relationship could provide a conceptual unifi- cation. Because of their reliance on a common resource, members of a guild have a similar role in the community [17]. It is the scientist’s interest in this ecological function (and the fact that such a function actually exists) that makes it appropriate to refer to the “forbivore guild of grasshoppers” or the “scavenger guild of grasshoppers”. An apropos use of the term is exemplified by Owen-Smith and Dankerts [33]: Grasshoppers in the Pyrgomorphidae, as well as certain of the Pamphagidae, Catantopinae and Tet- tigoniidae, feed primarily on forbs and small shrubs. Evidently nibbling by the grasshopper guild is more evenly spaced over the herbaceous layer than is grazing by ungulates. “Guild” is presumably uncommon in the acridological literature because of the relatively narrow specificity of the research interest. The diverse feeding habits of grasshoppers means that they are collectively subsumed under herbivory (detritivorous and necrophagous behaviors notwithstand- ing), and to refer to the “herbivore guild” (or even the “insect herbivore guild”) would entail many taxa other than Acrididae or Orthoptera. However, there would appear to be some cases in which grasshoppers can be reasonably understood to comprise a guild. 4.5. Terminological Perspectivism. The terms used for groups of grasshoppers should (and often do) reflect the interests of the scientist, such that others can reasonably infer the ecological or other perspective of a particular study. There may well be more terms for groups than I have analyzed here, and should these alternatives more effectively communicate the nature of an investigation they ought to be used. However, the descriptors in Table 1 represent the most common terms used by acridologists and ecologists and cover many, perhaps most, of the ways that we perceive grasshoppers in the field. 5. Summary: The Pragmatist’s View of the Right Term for a Group of Grasshoppers No investigation of a group of grasshoppers is motivated by all of the interests pertinent to acridology. For example, if one is attempting to understand the interactions among individuals within a given year, then it is not plausible to be also investigating the environmental factors associated with 8 Psyche the numerical dynamics of the group over the course of a century. But neither is it defensible to contend that one or the other of these perspectives is better or somehow more reflective of actual groups of insects in the world. We might think of the ways of perceiving a group of grasshoppers as being ecological lenses. The features visible through the “community lens” are not evident via the “population lens”. Giere [10] recognized the importance of understanding scientific inquiries as partial truths when he argued the following: [T]his multiple rootedness need not lead to “any- thing goes” perspectival relativism, or an anti- naturalist worship of common sense, experience, or language. It yields a kind of multi-perspectival realism anchored in the heterogeneity of “piecewise” complementary approaches common in biology and the study of complex systems. At this point, one might reasonably wonder about the nature of truth for the advocates of constrained per- spectivism. Is terminology merely a matter of linguistic convention or can we assert that a term is correct? The philosophy of pragmatism entails what has been called radi- cal empiricism [34], an approach consonant with scientific inquiry. We know what is true via our testing of ideas through their application in the world. The pragmatists eschewed debates about ontology and metaphysics that were not based on biophysical evidence. Arguing about reality and its properties was a fruitless endeavor unless there were actual consequences of being right (or wrong). This view gave rise to Richard Rorty’s analysis that truth is the compliment we pay to ideas that work [11]. What then does it mean for an idea to “work”? According to the pragmatists, an idea worked if it served as the basis for an action resulting in an outcome that satisfied genuine (not superficial or merely expedient) needs and desires. In short, an idea was true if it led to behaviors that fulfilled our interests as human beings. It is this concept that allows one to assert that a particular term for a group of grasshoppers is the right one. The test of whether “grasshopper population” or “grasshopper community” is a true description of a group of these insects is rather straightforward. Does adopting a particular perspective and using the associated term allow us to act in the world in ways that accord with our interests (both with regard to understanding the organisms and being understood by our colleagues)? The term “grasshopper population” is the right choice if this conceptual framework facilitates our investigation of a feature of the group (e.g., the rate of change in the density of the insects by the application of an appropriate model) and conveys to others the nature of our inquiry (e.g., our investigation concerns spatiotemporal dynamics rather than interactions structuring the group or other possible interests). In this pragmatic context, I would propose that one of the reasons why pest management of rangeland grasshop- pers is often conducted with nominal regard to beneficial and innocuous acridid species is the conceptual lumping that follows from referring to “grasshopper population outbreaks”. In effect, treatment programs target all of the grasshopper species which are amalgamated into a single group of pestiferous insects. And such homogenization can have highly deleterious consequences, such as the inadvertent suppression of high densities of beneficial species [35]. One has to wonder whether such mistakes might be avoided if we focused on ecological relations and referred to treatments of “grasshopper communities”. Such a terminological shift might entail our paying significantly greater attention to the more ecologically complex functions of these insects. In this context, treating a “grasshopper assemblage” might be politically expedient but fail to convey the environmental concerns that attend pest management interventions. As scientists, we want to pick out “natural kinds” in the world — those groups that represent objective, mind- independent collections of individuals [36, 37]. And there is reason to believe, for example, that “all of the grasshoppers that eat forbs” in a given habitat reflects an actual ecological group of individuals much more so than “all grasshoppers that were named by Samuel Hubbard Scudder”. In the end, however, the pragmatist recognizes that we do not have direct access to the way the world really is; we cannot know if our perspective uniquely or wholly corresponds with objective reality. What we can know is whether reality exists in such a way that our acting as if a group was real leads to actions that yield results consistent with human needs and wants. The right term for a group of grasshoppers is one that picks out and communicates one of a large number of “useful kinds” [11] — and it is my hope that this paper has made some practical contribution to our understanding of the natural world and one another. 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Hindawi Publishing Corporation Psyche Volume 201 1, Article ID 974646, 7 pages doi: 10. 11 55/201 1/974646 Research Article Mites (Acari) Associated with the Desert Seed Harvester Ant, Messor pergandei (Mayr) Kaitlin A. Uppstrom 1 and Hans Klompen 2 1 Department of Zoology, Miami University, Oxford, OH 45056, USA 2 Acarology Laboratory, Ohio State University, Columbus, OH 43212, Ohio, USA Correspondence should be addressed to Kaitlin A. Uppstrom, uppstrka@muohio.edu Received 29 October 2010; Accepted 18 January 2011 Academic Editor: Robert Matthews Copyright © 2011 K. A. Uppstrom and H. Klompen. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Mites (Acari) associated with the seed harvester ant Messor pergandei were investigated in the Sonoran desert of Arizona. At least seven representatives of the mite genera Armacarus, Lemanniella, Petalomium, Forcellinia, Histiostoma, Unguidispus, and Cosmoglyphus are phoretically associated with M. pergandei. Most of these morphospecies show preference for specific phoretic attachment sites and primarily use female alates rather than male alates for dispersal. Five mite morphospecies were found in low numbers inhabiting the chaff piles: Tydeidae sp., Procaeculus sp., Anystidae sp., Bakerdania sp., and Tetranychidae sp. The phoretic Petalomium sp. was observed consuming fungus growing on a dead queen, but the roles of the other mite species remain mostly unresolved. 1. Introduction The Sonoran Desert occupies the southwestern portion of Arizona and extends into California and Mexico. It is a harsh environment characterized by little rainfall, widely spaced shrubby vegetation, saguaro cacti, sandy soil, and high summer temperatures [ 1 ] . Seed harvesting by some desert ants is an adaptation to the lack of typical ant resources such as prey or honeydew from homopterans [2]. Harvester ants increase seed disper- sal, protection, and provide nutrients that increase seedling survivorship of the desert plants [2-5]. In addition, ants provide soil aeration through the creation of galleries and chambers, mix deep and upper layers of soil, and incorporate organic refuse into the soil [6]. Messor pergandei (Mayr) (length: 2.5-7 mm) is one of the most conspicuous and thoroughly studied species of seed harvesters found in the southwestern United States. This species forms populous, long-lived colonies with an estimated 30,000 to 50,000 workers [7, 8]. Its nests have been estimated to span 15.5 m in underground diameter, and extending to a depth of 4 m [2]. Nests have conspicuous crater entrances (usually 2-3 per nest), which are surrounded by chaff (refuse) piles [9]. Mating flights in this species occur primarily in February when temperatures reach approxi- mately 22°C [10]. Mites (Acari) often attach to larger arthropods for dispersal (phoresy). Through this primarily commensal relationship, mites are able to exploit scattered habitats more successfully than they would be able to do without external assistance [11]. Often phoretic mites are so synchronized with their hosts that they are able to detect subtle changes in life cycle or other aspects of their host species. For example it has been documented that if the host’s sex determines the mites’ continued survival or transport to a habitat, the mites board the sexes differentially [12], Previous work on ant associated mites has been limited primarily to descriptions of new species. The majority of ecological studies regarding myrmecophiles has focused on large arthropods (often Coleoptera), and most of the studies refer to the Acari recovered from the nest as simply “mites” or at another broad taxonomic level which provides little insight into the possible roles of the mites within the ant colonies [13-15], The biology, behavior, and ecology of M. pergandei have been studied in detail, but no previous publications have 2 Psyche mentioned arthropod associates of this common desert ant species. Mites known to be associated with other Messor species are shown in Table 1. All of these records are Middle Eastern or European and most (except two scutacarid species) are large mesostigmatid mites. Earlier (1997, 2007) unpublished collections by S. W. Rissing and W. H. Schaedla from M. pergandei alates (unmated winged reproductives), included small numbers of Petalomium sp. (Heterostig- matina: Pygmephoridae), Cosmoglyphus sp., Forcellinia sp. (Astigmatina: Acaridae), and Lemanniella sp. (Astigmatina: Lemanniellidae). The latter marked the first record of this family in the United States. What is unclear is whether this assemblage represents the complete set of mite species associated with M. pergandei. The following study was implemented to: (1) generate a complete list of the phoretic mite species associated with M. pergandei alates, (2) determine the phoretic attachment sites of the mite species, (3) test if phoretic mites show preference for female rather than male hosts, and (4) suggest possible roles of the mites in the ant colonies. 2. Methods 2.1. Collection Dates and Localities. The majority of the mites from M. pergandei nests were collected at: USA., Arizona, Pinal County, Casa Grande, W McCartney Rd, East of I- 10 (32.9398° N, 111.6641° W). A couple of collections occurred at a nearby site: N Cox Rd at W McCartney Rd, East of I- 10 (32.9299° N, 111.6891° W). The dominant vegetation in the study area is the creosote bush, Larrea sp., with small numbers of saguaro, Carnegiea gigantea Britton & Rose. Collections were made from 12-22 February 2008. The two sites are located near to each other and match those of the Rissing and Schaedla collections. 2.2. Field Collection Methods. Alates were collected prior to the mating flights by excavating the upper chambers of the nests around the entrances (to a depth of approximately 30- 60 cm). If alates were present, excavation continued until no further alates were found. Alates were deposited individually into empty 2 mL Eppendorf tubes labeled chronologically on the lids. Tubes with alates from different colonies were placed into separate plastic bags and labeled with a field number. If no alates were apparent after multiple excavation attempts at all entrances, the colony was assumed to not have any accessible alates. After returning from the field, live alates were carefully examined for phoretic mites using a stereomicroscope (25-50x). Each ant’s field number, sex, and the number and location of phoretic mites were recorded. Alates were returned to their original Eppendorf tubes and preserved in 95% ethanol. The numbers of ants with and without mites for each colony were recorded for prevalence calculations (number of infested hosts/number of hosts examined) [21], Chaff accumulates as a contiguous mass outside of active nest entrances and can be easily peeled up from the sand. Chaff piles were collected from six nests (multiple entrances of the same nest were combined) prior to excavation for alates and enclosed in 473 mL clear plastic deli containers for transport. Collapsible nylon Berlese funnels (using 40 watt bulbs) were hung in a garage for two days to extract any chaff- inhabiting mites into 100 mL Nasco Whirl-Paks half filled with 95% ethanol. 2.3. Recovery and Preservation of Mites from Ants and Chaff. All collections (ants and chaff products) were transported to the Acarology Laboratory at Ohio State University. Contents of the Eppendorf tubes holding the alates with phoretic mites were examined, mites were counted, and representatives were cleared in lactophenol then mounted on slides in Hoyer’s-Strandtmann’s medium. Berleseates from chaff were searched for mites, and exemplars of each morphospecies were also mounted on slides. Mites were rarely observed still clinging to the host in the ethanol tubes. Therefore original mite attachment sites on host alates were determined by merging lab and field notes; the number of mites of each species recovered from a host was compared to field notes documenting the number at each bodily location. Specimens that were documented in the field, but not subsequently recovered in the lab were not included in the attachment site specificity summary (Table 5). Mites which were undocumented in the field, but later found in the tubes were categorized as specimens with “unknown” phoretic locations. 2.4. Mite Identification and Vouchers. Mites were identified using a published key to families of Astigmatina [22] and an unpublished key to the genera of Acaridae (OConnor, pers. comm.), Savulkina’s [23] generic key for pygmephoroids (Heterostigmatina), and Walter et al.’s [24] key to families of soil Prostigmata. Attempts to identify the phoretic taxa to species failed, as none of these taxa matched available descriptions. Consequently, mites were identified to mor- phospecies (called “species” throughout the text). Voucher specimens for all mite species are deposited in the Ohio State University Acarology Collection (OSAL) under the following names and accession numbers (total number of slides for each species in parentheses): Armacarus Messor spl (71)-OSAL0007082, Lemanniella Messor spl (28)-OSAL0007039, Petalomium Messor spl (36)- OSAL0007035, Forcellinia Messor spl (2)-OSAL0007105, Histiostoma Messor spl (2)-OSAL0092942, Unguidispus Messor spl (1)-OSAL0007060, Nanorchestidae Messor spl ( 1 )-OSAL0092938, Tydeidae Messor spl (7) -OSAL0 102747, Procaeculus Messor spl (l)-OSALOl 02748, Anystidae Messor spl (1)-OSAL0102750, Bakerdania Messor spl (1)-OSAL0102740, and Tetranychidae Messor spl (1)- OSALO 102749. A voucher specimen of Messor pergandei is deposited in the Ohio State University Insect Collection under accession number OSUC0359951. 2.5. Statistical Analysis. The proportions of infested male and female alates were analyzed using a logit model with the log odds ratio of the proportion of individuals infected (prevalence) and the proportion uninfected as the response variable and sex as a categorical predictor variable. Analyses Psyche 3 Table 1: A list of mite species associated with ants of the genus Messor. Generic names follow current taxonomic standing. Messor species Mite family Mite species Association Location Reference M. harharus Messoracaridae Messoracarus mirandus Silvestri On head Italy [16] M. capitatus Laelapidae Myrmozercon acuminatus (Berlese) In nest Italy [17] Laelapidae Myrmozercon brachiatus (Berlese) In nest Italy [17] M. excursionis Laelapidae Laelaps ( Hypoaspis ) intermedius (Karawajew) (1) In nest Turkmenistan [18] Scutacaridae Imparipes placidus Khaustov & Chydyrov In nest Turkmenistan [19] Circocyllibanidae Cillibano transversalis (Karawajew) (1) In nest Turkmenistan [18] M. meridionalis Oplitidae Oplitis inopina (Hull) In nest Iran [20] Oplitidae Oplitis leonardiana (Berlese) In nest Italy [17] M. structor Oplitidae Oplitis philoctena (Trouessart) In nest Italy [17] Laelapidae Gymnolaelaps myrmophilus (Michael) In nest Czechoslovakia [20] Trachyuropodidae Trachyuropoda magna (Leonardi) In nest Czechoslovakia [20] Messor sp. Scutacaridae Imparipes ignotus Khaustov 8c Chydyrov In nest Turkmenistan [19] (1) The taxonomic status of the two Karawajew species is unclear, their descriptions are incomplete, and we have found no record of use of these names since the original description [ 18] . Karawajew does note that his Laelaps intermedius is intermediate between L. myrmecophilus Berlese and L. myrmophilus Michael. Both are currently placed in the genus Gymnolaelaps. were conducted using the glm function in the base package of R software [25]. Due to low collections of mites on male alates (and many zeros in the data), the data were overdis- persed relative to the binomial distribution. Likelihood ratio tests were used to compare the following models: Ml - intercept with overdispersion (null model) versus M2 - intercept + sex + overdispersion, and M2 versus M3 - sex + colony sex ratio (proportion of colony comprised of male or female alates) + overdispersion. We hypothesized that the effect of sex would be a significant variable predicting mite prevalence (M2). Alate sex ratio (M3) of the colony would not be significant unless mites were simply boarding hosts based on abundance of the sex within the colony. 3. Results 3.1. Colony Collections. A total of 330 alates (140 males, 190 females) was collected from 16 ant colonies. Numbers of alates ranged from 2 to 61 per colony. Most colonies produced both sexes, but sex ratios were usually skewed towards one sex or the other. Five colonies were collected with only males or females (Table 2). Phoretic mites were present on alates in 8 of the 16 colonies. 3.2. Mite Association with Female versus Male Alates. A total of 90 male and 150 female alates was collected from the 8 mite infested colonies and 88 total alates had phoretic mites (see Table 2). Average infestation rates across the 8 infested colonies were 6.7% for males {N = 6) and 54.7% for females {N = 82). The mean number of mites per male alate in infested colonies was 1.67 (range 1 to 2, SD = 0.41, median = 1); female alates had a mean of 7.15 (range 1-30, SD = 7.10, median = 5). A total of 98% of the mite specimens was collected from female alates. The results of the generalized linear regression analysis showed the effect of sex (M2) to be of borderline Table 2: Total number of male (M) and female (F) alates collected per colony of the ant Messor pergandei and abundance of associated phoretic mites. Colony Total M Total F # M with mites # F with mites 1 15 6 2 6 2 9 48 0 11 3 7 30 0 6 4 2 1 0 0 5 1 1 3 0 2 6 0 10 — 7 7 0 1 — 0 8 5 1 0 0 9 1 0 2 — 2 10 0 4 — 0 11 56 5 4 2 12 2 46 0 46 13 14 0 0 — 14 4 13 0 0 15 10 16 0 0 16 15 4 0 0 1 Two colonies collected at the Cox Rd site. All other colonies were collected at the W McCartney Rd site. Dashed lines mean no alates of that sex were present within the colony. significance (P = .0548). The likelihood ratio test for Ml (overdispersion null model) versus M2 was significant (P = .008), indicating that effect of sex is a strong predictor of alate infestation probability. Sex ratio was not a significant variable in the model alone (P = .271) or with effect of sex, as in M3 (P = .309). The Analysis of Deviance table and predicted and observed prevalence for mites on males and females (using M2) are shown in Table 3. Mites showed significant preference for females independent of the available sex ratio within the colony. 4 Psyche Table 3: Host sex preference of phoretic mites, (a) Analysis of Deviance table. Results of the comparison of the null model (Ml) and the model with sex included (M2), (b) Observed and predicted (using Model 2) male and female infestation prevalence values. (a) Analysis of deviance table Model df Resid. Dev. df Deviance Resid. P(>|Chi|) Ml null 32 309.36 M2 sex 33 382.74 1 73.38 0.0076 (b) Prevalence probabilities Sex Obs. Prob. Std. Error Obs. Pred. Prob M 0.017 0.52 0.043 F 0.35 1.91 0.43 3.3. Phoretic Mite Species and Abundance. The total of 593 mite specimens recovered comprised representatives of 6 genera: Lemanniella , Petalomium , Forcellinia, Armacarus (Acaridae), Histiostoma (Atigmatina: Histiostomatidae), and Unguidispus (Heterostigmatina: Microdispidae). One mite specimen belonging to the family Nanorchestidae was found in a vial with a female alate, but is likely a contaminant from soil. Armacarus sp. comprised 83% of the mites collected; however, 488 of 490 specimens were found in a single colony. Lemanniella sp. and Petalomium sp. comprised 10% and 7% of the collections, respectively. Forcellinia sp., Histiostoma sp. and Unguidispus sp. were collected as doubletons or singletons. Mite abundances and their host sex preferences are shown in Table 4. 3.4. Attachment Site Specificity. Observation of living ant specimens prior to placement in alcohol is necessary to gain a clear understanding of the mite phoretic attachment sites, as phoretics do not hold on to their host in alcohol. The number of mites found at specific phoretic locations on the host is presented in Table 5. Armacarus sp. were found on various sites on the host, but the majority (388 of the 490 mites) were found attached anterior-ventrally to the gaster. Armacarus sp. individuals would often arrange themselves in the same direction, with legs I oriented toward the posterior end of the ant. Lemanniella sp. were found primarily (48 of 56 mites) under the head, beneath the psammophore (beard- like hairs found in desert ant species, used for movement of sand). Petalomium sp. were generally (29 of 42 mites) found in the ventral position, particularly between the second and third coxae. Forcellinia, Histiostoma, and Unguidispus sp. were found in too low of numbers to make generalizations concerning their phoretic locations. Precise documentation of mite attachment sites is diffi- cult and depends on the method of collection. Rettenmeyer [26] collected mites from army ants using jars with ether, but noted that the mites often became caught in condensation on the jar walls and subsequently lost. Freezing may be an alternative, but any manipulation of dead ants may result in the release of mites from their sites of phoretic attachment. Moreover, thawing can cause the same issues through vapor condensation. 3.5. Mites in Chaff Piles. Only 3 of the 6 chaff piles hosted mites, generally in low numbers. The majority of mites recovered from chaff piles were small, soft bodied Prostigmata. With the exception of one, a very abundant species found in two chaff piles, Tydeidae sp., most of them, such as Procaeculus sp. (Caeculidae), Anystidae sp., Tetranychidae sp., and a nonphoretic female of Baker dania sp. (Pygmephoridae) were singletons. 4. Discussion 4.1. Yearly Variation and Phoretic Mite Species Richness. Representatives of 6 mite genera Armacarus, Lemanniella, Petalomium, Forcellinia, Histiostoma, and Unguidisipus were found associated phoretically with M. pergandei alates. The 1997 and 2007 collections by Rissing and Schaedla included Cosmoglyphus sp., a species not collected in this study. In contrast they were lacking Armacarus sp., the most abundant mite species encountered in this study (primarily in a single colony). It is likely that mite populations exhibit fluctuations in abundance and ubiquity in different years. The mite community may also change in composition throughout the year depending on resource availability. This could not be tested, however, because all of the mites collected in 1997, 2007, and 2008 were collected in February and March, months in which opportunity of dispersal to new colonies by alates is the greatest. To obtain a complete list of ant-associated mites and their yearly or seasonal cycles, a continual sampling regime is required. 4.2. Attachment Site and Host Sex Specificity of Phoretic Mites. Attachment site specificity is apparent in the frequently sampled mite species, Armacarus sp., Lemanniella sp., and Petalomium sp. Although most mites were found in several locations on the alates, a preference for one or a couple of key locations is apparent. In highly infested ants, the mites commonly spilled over to locations beyond their primary attachment sites; however, when only a few mite individuals were present, they were found primarily at their preferred locations on males as well as females. For example, Lemanniella sp. rode on the underside of the ants’ heads, in both males and females, even though M. pergandei males have much smaller heads and less developed psammophores than the females. How the mites select and distribute themselves at attachment locations remains unresolved. Mites showed a marked preference for female alate hosts, and except Unguidispus sp., which was represented by a singleton, the majority of the representative specimens (98.8%) were found on female alates. Male M. pergandei die soon after mating, as is the case for most ant species. Apparently to select a female host is an advantage for a mite requiring resources in the ant nest. The desiccating desert environment provides little time for survival on a dead male host, and this also supports selection for a female host. Mites can be transported back to a nest by way of necrophagic Psyche 5 Table 4: Number of representative specimens of the six mite genera found on male (M) and female (F) alates on Messor pergandei. Colony (1) Armacarus M F Lemanniella M F Petalomium M F Forcellinia F Histiostoma F Unguidispus M Total 1 0 1 2 15 0 2 0 0 1 20 2 0 0 0 0 0 13 0 0 0 13 3 0 0 0 0 0 6 0 0 0 6 5 0 0 0 9 0 0 0 0 0 9 6 0 0 0 20 0 2 0 0 0 22 9 0 0 0 6 0 4 0 0 0 10 11 0 1 0 0 4 1 0 0 0 6 12 0 488 0 4 0 10 2 2 0 507 Total 0 490 2 54 4 38 2 2 1 593 Abundance (%) 82.63 9.44 7.08 0.34 0.34 0.17 ( 1) Colony number corresponds to those listed in Table 2. Table 5: Attachment site preferences for phoretic mite species on Messor pergandei. Location Armacarus Lemanniella Petalomium Forcellinia Histiostoma Unguidispus Ventral head 7 48 0 0 1 1 Neck 0 0 3 0 0 0 Dorsal thorax 28 1 1 0 0 0 Lateral thorax 11 0 0 0 0 0 Ventral coxae 6 0 29 0 0 0 On leg 11 0 3 2 0 0 Petiole 16 0 0 0 0 0 Gaster 388 0 0 0 0 0 Unknown 23 7 6 0 1 0 Total 490 56 42 2 2 1 activity by ants, and the scarcity of resources in the desert may increase the frequency of necrophagy. The seven mites associated with male ants occurred in two colonies with male-biased sex ratios. In all female-biased colonies only females carried mites. This may indicate that host sex preference is strongly influenced by host availability rather than sex of the host. However, it is more likely that males are infested in situations in which females are rare or more difficult to find. This idea is supported by the lack of significance for the model including sex ratio (M3). In cases of phoretic mites on males, males were more abundant than females in the nest, yet smaller percentages of males were found with mites. Other studies have shown similar preference for females. Ebermann and Moser [27] collected five species of mites in the family Scutacaridae associated with red imported fire ant alates ( Solenopsis invicta Buren) in Louisiana. In another study of the red imported fire ant, mites in the genus Histiostoma also showed preference for females [28]. Our study provides further support for this type of mite host selection on a previously unexplored ant genus. 4.3. Mites in Chaff Piles. Chaff piles appear to comprise little mite diversity. Chaff was very dry despite recent rain in the area; humidity is probably the main factor influencing mite abundance and diversity in the chaff pile. The piles are primarily composed of seed husks and small pieces of plants, but seem to be cemented together by fungal mycelia. The Bakerdania sp. was likely feeding on fungus, as most species of the family Pygmephoridae do. Procaeculus sp. and Anystidae sp. are predators, and tetranychid mites are plant feeders. The latter may have been deposited in the chaff on plant material refuse by ants. Mites of the family Tydeidae are fungivores, predators, and pollen feeders and their role in chaff piles remains unresolved. 4.4. Possible Roles of Phoretic Mites. During phoresy no harm or benefit is brought upon the host, and once the host reaches a suitable habitat, the mite will disembark, develop into a feeding instar, and subsequently reproduce [11]. Mites in the genera Petalomium and Unguidispus have stylet-like chelicerae that are typical of fungivores. Many of them are feeding specialists, and during phoresy, they may carry fungal spores in order to inoculate their habitat [29, 30]. Laboratory rearing has documented that the mite Petalomium fibrisetum Ebermann & Rack, associated with Lasius flavus (Labricius), fed on hyphae of various fungi available in ant nests. In this mite species a lack of food triggered development of phoretic females [31]. In our study, Petalomium sp. was observed feeding on a white fungus growing on a dead 6 Psyche M. pergandei queen in the laboratory, providing further support for fungivorous habits. Fungivory by mites may be beneficial to the ant colonies, particularly if the mites control entomopathogenic fungi, or fungi growing on food stores. Numerous fungal species exist in ant colonies and soil habitats, so commensalism in the ant colonies can be expected. Observations concerning the role of astigmatid mites in ant nests are rare in the literature. Mites of the genera Forcellinia, Cosmoglyphus, Armacarus and Lemanniella are almost exclusively found in association with ants, but pub- lished biological observations are restricted to Lemanniella. Lemanniella minotauri Wurst was reared in a laboratory, and its feeding instars were observed to be ingesting a black fungus growing in Lasius brunneus (Latreille) nests. Lemanniella minotauri was also observed riding under the head of the I. brunneus host [32], Chelicerae of mites of the family Flistiostomatidae are modified into feathery filter-feeding structures. These mites tend to inhabit wet substrates where they filter and ingest organic material and microorganisms. Some mutualistic mites of the genus Anoetus remove pathogenic microorgan- isms from pollen and nectar in the nests of halictid bees [22] . Histiostoma polypori (Oudemans) was observed developing and feeding on a decaying earwig host after it had died [33]. Phoretic deutonymphs of Histiostoma sp. associated with M. pergandei might ingest bacteria within the ant nest as later instars or await the death of their hosts to feed on them as scavengers. It is unlikely that any of the mite species collected on M. pergandei are ectoparasites of these ants. More likely these mites, after their phoretic stage, become commensals or mutualists, eating fungi and bacteria within the nest. Acknowledgments The authors thank Steve Rissing for guidance and suggestions regarding the collection of M. pergandei, Susan Jones for edits and comments on earlier drafts, Tom Crist for assistance with the statistical analyses, Shellie and Robb Hjellum for room and board in Arizona, Joe Raczkowski for collection suggestions and valuable conversations, Bob Johnson for collection of information and the use of his equipment, and Clint Penick for assistance in the field. References [1] G. C. Wheeler and J. Wheeler, Ants of Deep Canyon, Philip L. Boyd Deep Canyon Desert Research Center, University of California, Riverside, Calif, USA, 1973. [2] T. Tevis Jr., “Interrelations between the harvester ant Veromes- sor pergandei (Mayr) and some desert ephemerals,” Ecology, vol. 39, pp. 695-704, 1958. [3] D. J. O’Dowd and M. E. Hay, “Mutualism between harvester ants and a desert ephemeral: seed escape from rodents,” Ecology, vol. 61, pp. 531-540, 1980. [4] S. W. Rissing, “Indirect effects of granivory by harvester ants: plant species composition and reproductive increase near ant nests,” Oecologia, vol. 68, no. 2, pp. 231-234, 1986. [5] Y. Steinberger, H. Leschner, and A. Shmida, “Chaff piles of harvester ant ( Messor spp.) nests in a desert ecosystem,” Insectes Sociaux, vol. 38, no. 3, pp. 241-250, 1991. [6] A. J. Beattie and D. C. Culver, “The nest chemistry of two seed- dispersing ant species,” Oecologia , vol. 56, no. 1, pp. 99-103, 1983. [7] R. A. Johnson, “Seed-harvester ants (Hymenoptera: Formici- dae) of North America: an overview of ecology and biogeog- raphy,” Sociobiology, vol. 36, no. 1, pp. 89-122, 2000. [8] R. A. Johnson, “Biogeograhy and community structure of North American seed-harvester ants,” Annual Review of Entomology, vol. 46, pp. 1-29, 2001. [9] J. Wheeler and S. W. Rissing, “Natural history of Veromessor pergandei — I. The nest,” The Pan-Pacific Entomologist, vol. 51, pp. 205-216, 1975. [10] R. A. Johnson, “Reproductive biology of the seed-harvester ants Messor julianus (Pergande) and Messor pergandei (Mayr) (Hymenoptera: Formicidae) in Baja California, Mexico,” Journal of Hymenoptera Research, vol. 9, pp. 377-384, 2000. [11] B. M. OConnor, “Evolutionary ecology of astigmatid mites,” Annual Review of Entomology, vol. 27, pp. 385-409, 1982. [12] N. J. Fashing, “The evolutionary modification of dispersal in Naiadacarus arboricola Fashing, a mite restricted to waterfilled treeholes (Acarina: Acaridae).,” American Midland Naturalist, vol. 95, pp. 337-346, 1976. [13] A. M. Boulton, B. A. Jaffee, and K. M. Scow, “Effects of a common harvester ant ( Messor andrei ) on richness and abundance of soil biota,” Applied Soil Ecology, vol. 23, no. 3, pp. 257-265, 2003. [ 14] D. Wagner, M. J. F. Brown, and D. M. Gordon, “Harvester ant nests, soil biota and soil chemistry,” Oecologia , vol. 112, no. 2, pp. 232-236, 1997. [15] V. Witte, A. Feingartner, F. Sabafi, R. Hashim, and S. Foitzik, “Symbiont microcosm in an ant society and the diversity of interspecific interactions,” Animal Behaviour, vol. 76, no. 5, pp. 1477-1486, 2008. [16] F. Silvestri, “Contribuzioni alia conoscenza dei mirmecofili,” Bollettino del Laboratorio di Zoologia Generale e Agraria della Facolta Agraria in Portici, vol. 6, pp. 222-245, 1912. [17] A. Berlese, “Illustrazione iconograflca degli Acari mirme- cofili” Redia, vol. 1903-1904, pp. 299-474, 1904. [18] W. Karawajew, “Myrmecophilen aus transkaspien,” Russkoe Entomologicheskoe Obozrenie, vol. 3, pp. 227-237, 1909. [19] A. A. Khaustov and P. R. Chydyrov, “New species of mites of the family Scutacaridae (Acari: Heterostigmata) associated with ants (Hymenoptera, Formicidae) from Turkmenistan,” Acarina, vol. 12, pp. 87-103, 2004. [20] J. E. Hull, “New myrmecophilous gamasids,” Annals and Magazine of Natural History, vol. 12, pp. 610-616, 1923. [21] F. Margolis, G. W. Esch, and J. C. Holmes, “The use of ecological terms in parasitology (report of an ad hoc committee of the American society of parasitologists) ,” Journal of Parasitology, vol. 68, no. 1, pp. 131-133, 1982. [22] B. M. OConnor, “Cohort astigmatina,” in Manual ofAcarology, G. W. Krantz and D. E. Walter, Eds., pp. 565-657, Texas Tech University Press, Fubbock, Tex, USA, 3rd edition, 2009. [23] M. M. Savulkina, “Systematics, ecology, and distribution of mites of the family Pygmephoridae Cross, 1965 (Acari, Trombidiformes),” Entomological Review, vol. 60, pp. 163-180, 1981. [24] D. E. Walter, E. E. Findquist, I. M. Smith, D. R. Cook, and G. W. Krantz, “Order Trombidiformes,” in A Manual of Psyche 7 Acarology, G. W. Krantz and D. E. Walter, Eds., pp. 233-420, Texas Tech University Press, Lubbock, Tex, USA, 3rd edition, 2009. [25] R Development Core Team, “The R foundation for Statistical Computing, ver 2.10,” Vienna University of Technology, Vienna, Austria, 2009, http://www.r-project.org/. [26] C. W. Rettenmeyer, Arthropods associated with neotropical army ants with a review of the behavior of these ants (Arthro- poda; Formicidae: Dorylinae), Ph.D. Dissertation, University of Kansas, Lawrence, Kan, USA, 1962. [27] E. Ebermann and J. C. Moser, “Mites (Acari: Scutacaridae) associated with the red imported fire ant, Solenopsis invicta buren (Elymenoptera: Formicidae), from Louisiana and Ten- nessee, U.S.A,” International Journal of Acarology, vol. 34, no. 1, pp. 55-69, 2008. [28] L M. Sokolov, Y. Y. Sokolova, and J. R. Fuxa, “Histiostomatid mites (Histiostomatidae: Astigmata: Acarina) from female reproductives of the red imported fire ant (Hymenoptera: Formicidae),” Journal of Entomological Science, vol. 38, no. 4, pp. 699-702, 2003. [29] E. Ebermann and M. Hall, “First record of sporothecae within the mite family Scutacaridae (Acari, Tarsonemina),” Zoologischer Anzeiger, vol. 242, no. 4, pp. 367-375, 2004. [30] E. Ebermann and M. Hall, “A new species of scutacarid mites transferring fungal spores (Acari, Tarsonemina),” Revue Suisse de Zoologie, vol. Ill, no. 4, pp. 941-950, 2004. [31] E. Ebermann and G. Rack, “Zur biologie einer neuen myrme- cophilen art der gattung Petalomium (Acari, Pygmephori- dae),” Entomologische Mitteilungen aus dem Zoologischen Museum Hamburg, vol. 115, pp. 175-191, 1982. [32] E. Wurst, “The life cycle of Lemanniella minotauri n. sp. and the erection of the new family Lemanniellidae (Acari: Astigmata),” Stuttgarter Beitrage zur Naturkunde. Serie A, vol. 621, pp. 1-34, 2001. [33] B. K. Behura, “The relationships of the tyroglyphoid mite, His- tiostoma polypori (Oud.) with the earwig, Forficula auricularia Linn,” Journal of the New York Entomological Society, vol. 64, pp. 85-94, 1956. Hindawi Publishing Corporation Psyche Volume 201 1, Article ID 578327, 4 pages doi: 10. 11 55/20 11/578327 Editorial Locusts and Grasshoppers: Behavior, Ecology, and Biogeography Alexandre Latchininsky , 1 Gregory Sword , 2,3 Michael Sergeev , 4,5 Maria Marta Cigliano , 6 and Michel Lecoq 7 1 Department of Renewable Resources, University of Wyoming, 1000 E. University Avenue, Laramie, WY 82071, USA 2 School of Biological Sciences, University of Sydney, Sydney, NSW 2006, Australia 3 Department of Entomology, Faculty of Ecology and Evolutionary Biology, Heep Building, Texas A&M University, College Station, TX 77842-2475, USA 4 Department of General Biology and Ecology, Novosibirsk State University, 2 Pirogova Street, Novosibirsk 630090, Russia 5 Laboratory of Insect Ecology, Institute of Systematics and Ecology of Animals, Siberian Branch, Russian Academy of Sciences, 1 1 Frunze Street, Novosibirsk 630091, Russia 6 Division Entomologia, Museo de La Plata, Universidad Nacional de la Plata, Paseo del Bosque S/N,1900 La Plata, Argentina 7 CIRAD Bioagresseurs, TA A- 106/D, Campus International de Baillarguet, 34398 Montpellier cedex 5, France Correspondence should be addressed to Alexandre Latchininsky, latchini@uwyo.edu Received 27 January 2011; Accepted 27 January 2011 Copyright © 2011 Alexandre Latchininsky et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Locusts and grasshoppers (L&G) (Orthoptera: Caelifera, Acridoidea) are an essential component of both, healthy, and disturbed grassland ecosystems. These insects are abundant in natural and anthropogenic habitats (rangelands, wetlands, agricultural fields, lawns, etc.). They stimulate plant growth, participate in nutrient cycling, and play important role in food chains [1-5]. Some grasshoppers are proposed as ecological indicators of ecosystem qualities and efficacy of ecological networks [6]. On the other hand, when their pop- ulations grow to catastrophic dimensions, L&G are among the most devastating enemies of agriculturists. Outbreaks of locusts such as Schistocerca gregaria (Forskal, 1775), Nomadacris septemfasciata (Serville, 1838), Locusta migra- toria Linnaeus, 1758, Calliptamus italicus (Linnaeus, 1758), Dociostaurus maroccanus (Thunberg, 1815), Chortoicetes terminifera (Walker, 1870), and many abundant grasshopper species continue to occur on all continents except Antarctica and affect the livelihoods of one in every ten people on Earth. Such L&G outbreaks are now better controlled and their frequency and size have been reduced with the application of preventative strategies [7, 8]. However, invasions still persist. During the outbreak of the Desert locust S. gregaria in Africa in 2003-2005, over eight million people suffered from severe 80 to 100% crop losses [9]. To combat the locust swarms, 13 million hectares in 22 countries on three continents were treated with broad-spectrum neurotoxins. Such transcontinental operation, including the food aid for affected population, cost over half a billion US dollars to the world community [10]. Losses to L&G are not limited to crop and rangeland destruction. Besides the economic damage and its subse- quent negative social impact, L&G outbreaks may seriously alter ecological processes across landscapes (e.g., carbon and water cycles). The rapid loss of vegetation cover may result in soil erosion and increased runoff. L&G can also destroy food sources for many animals and thus affect biodiversity; such effects may be particularly pronounced in isolated insular ecosystems [11]. Large-scale L&G control programs can also affect biodiversity, including that of nontarget grasshoppers [12]. Despite decades of intensive research, the mechanisms underlying L&G population dynamics (and for locusts: phase transformation) are not fully elucidated. Only recently, significant advances were made in our understanding of L&G behavior and ecology, particularly individual and group movement, nutritional requirements, and biochemical mechanisms underlying the transformation between solitarious and gregarious locust phases [13-15]; see also review in [16]. 2 Psyche Besides the notorious pests, this group of insects includes many understated rare species which require protection [17— 19]. To complicate the picture, following landscape changes induced by human agricultural activities, some economic pests may become exceedingly rare [20]. On the other hand, many orthopteran species benefit from human-induced landscape changes and increase their abundance [18, 21]. Disturbed and new habitats can be important for spreading and living of some native and alien grasshopper forms [18, 21, 22]. At the same time, many of rare grasshopper species are threatened by anthropogenic influences, such as overgrazing and ploughing [18]. However, in various areas, such as temperate Eurasia or in Tropical Madagascar, several centers of orthopteran diversity and endemism overlap with areas of frequent L&G outbreaks [23-25]. This means that problems of plant protection and conservation biology should be solved on the complex basis of a holistic approach. However, it is hardly ever the case; pests and rare species are usually studied separately, and their possible relationships are not explored. Although the general patterns of grasshopper distribu- tion are described for different regions [26-28], the main factors and processes determining grasshopper diversity patterns at different scales are still under discussion. Impor- tance of temperatures and precipitation is evident, but the distribution of many species, populations, and assemblages could not be explained by macroclimatic factors only [29]. This means that the role of other factors and processes should be investigated more thoroughly. At a regional level, it is possible to establish the general pattern of regional biodiver- sity and explain how the spatial distribution of populations permits species with various origins and different ecological preferences to coexist [30]. An example of this approach is the opening article for this special issue of Psyche, in which M. G. Sergeev reviews distribution patterns of over 130 species of grasshoppers and their kin in the boreal zone. Grasshoppers and their relatives occupy there almost exclusively open habitats, such as meadows, mountain steppes and tundras, clearings, open- ings, bogs, and stony flood plains. The boreal orthopteroid assemblages exhibit low species diversity and abundance. Based on the biogeographic analysis, the author concludes that relationships between the faunas of the Eurasian and North American parts of the boreal zone are relatively weak. Local grasshopper distribution patterns have been dis- cussed since the beginning of the 20th century. Possible relationships between grasshopper diversity, plant species composition, and habitat structure have been discussed for many decades. The paper of D. H. Branson (second in this special issue) provides an example of such studies. The author found these relationships too complicated for simple explanations. The type, level, strength, and complexity of these relationships may be determined not only by local but also by regional patterns. Consequently, to evaluate general trends in grasshopper diversity one should study all main regions and ecosystems in the same manner. This idea may serve as a basis for an ambitious regional study. The third paper of the special issue is devoted to a complex terminological issue. Acridologists have used a variety of terms to describe groups of grasshoppers, includ- ing assemblage, community, guild, and population. This terminological diversity has raised the question of whether one of these descriptors is the correct one. The author, J. A. Lockwood, argues that a term is correct if it accurately reflects the conceptual framework of the investigator and effectively communicates this perspective to others. He describes the contexts in which the most common terms are appropriate. In the next paper, O. Olfert et al. investigate the impact of climate changes on distribution and relative abundance of a pest grasshopper of major economic importance in North America, Melanoplus sanguinipes. Various scenarios of climatic changes were used to parameterize a bioclimatic model of this species. Compared to predicted range and distribution under current climate conditions, model results indicated that M. sanguinipes would have increased range and relative abundance in more northern regions of North America. Conversely, model output predicted that the range of this crop pest could contract in regions where climate conditions became limiting. However, some caution has been expressed by authors. The impact of biotic factors such as natural enemies should also be considered, and bioclimatic modeling of grasshopper populations will surely benefit in the future from a multitrophic approach (host plants- grasshoppers-natural enemies). The fifth paper of this special issue by H. Song reviews the current state-of-the-art regarding locust phase polyphenism in species other than the two model locusts. Although the mechanisms of locust phase transformation are relatively well understood for the Desert locust and the Migratory locust, they remain largely obscure in nonmodel locust species. The author found similar density-dependent pheno- typic plasticity among closely related species. He emphasized the importance of comparative analyses in understanding the evolution of locust phase and proposed a phylogeny-based research framework for future analyses. In the next paper M. Lecoq et al. present a typology quan- tifying density-dependent color change in the Red locust nymphs. This information can contribute to improving the reliability of the data collected by the National Locust Centers when surveying this major pest. The authors, in Madagascar, sampled hoppers from several populations of different density and measured the color of different body parts as categorical variables. They found that color change is positively correlated with population density. This study is an important contribution to our knowledge of locust coloration in the field, for which there is currently a weaker understanding than that for laboratory populations. The seventh paper of this special issue by S. O. Ely et al. discusses the diel behavioral activity patterns of solitarious Desert locust adults. The authors found that the insects were more attracted to volatiles from potted Heliotropium ovalifolium in scotophase than in photophase. The attraction towards the host plant odors, in both photophase and scotophase, concurs with previous observations on locust oviposition preferences near these plants. Psyche 3 In the eighth paper, R. B. Srygley and S. T. Jaronski report experiments with Beauveria bassiana (Fungi: Ascomycota), an entomopathogenic fungus that serves as a biological con- trol agent of Mormon crickets Anabrus simplex Haldeman (Orthoptera: Tettigoniidae) and other grasshopper pests. They demonstrated an immune response of infected Mor- mon crickets and concluded that circulating phenoloxidase may be an important enzymatic defense against Beauveria infection, and that it is associated with attempted clearing of Beauveria blastospores and hyphae from Mormon cricket hemolymph. Alexandre Latchininsky Gregory Sword Michael Sergeev Maria Marta Cigliano Michel Lecoq References [1] I. V. Stebaev, “Periodic changes in the ecological distribution of grasshoppers in the temperate and the extreme continental steppe regions, and their importance for the local ecosystems,” in Proceedings of the International Study Conference on the Current and Future Problems of Acridology, pp. 207-213, Centre for Overseas Pest Research, London, UK, 1972. [2] G. B. Hewitt and J. A. Onsager, “A method for forecasting potential losses from grasshopper feeding on northern mixed prairie forages ,” Journal of Range Management , vol. 35, pp. 53- 57, 1982. [3] O. O. Olfert and M. K. Mukerji, “Effects of acute simulated and acute grasshopper (Orthoptera: Acrididae) damage on growth rates and yield in spring wheat ( Triticum aestivum),” The Canadian Entomologist , vol. 115, no. 6, pp. 629-639, 1983. [4] M. G. Sergeev, “Zonal-landscape distribution of Orthoptera zoomass in Middle Region of the USSR,” Geographia i Prirodnyje Resursy, no. 2, pp. 89-92, 1989 (Russian). [5] G. E. Belovsky, “Do grasshoppers diminish grassland produc- tivity? A new perspective for control based on conservation,” in Grasshoppers and Grassland Health. Managing Grasshopper Outbreaks without Risking Environmental Disaster, J. A. Lock- wood, A. V. Latchininsky, and M. G. Sergeev, Eds., pp. 7-30, Kluwer Academic Publishers, Dordrecht, Netherlands, 2000. [6] C. S. Bazelet, Grasshopper bioindicators of effective large-scale ecological networks, Ph.D. Dissertation, Department of Con- servation Ecology and Entomology, Stellenbosch University, South Africa, 2011. [7] J. I. Magor, M. Lecoq, and D. M. Hunter, “Preventive control and Desert Locust plagues,” Crop Protection, vol. 27, no. 12, pp. 1527-1533,2008. [8] G. A. Sword, M. Lecoq, and S. J. Simpson, “Phase polyphenism and preventative locust management,” Journal of Insect Physi- ology, vol. 56, no. 8, pp. 949-957, 2010. [9] L. Brader, H. Djibo, and F. G. Faye, Towards a more Effective Response to Desert Locusts and Their Impacts on Food Insecurity, Livelihoods and Poverty. Independent Multilateral Evaluation of the 2003-2005 Desert Locust Campaign, FAO, Rome, Italy, 2005. [10] Y. T. Belayneh, “Acridid pest management in the developing world: a challenge to the rural population, a dilemma to the international community,” Journal of Orthoptera Research, vol. 14, no. 2, pp. 187-195, 2005. [11] A. V. Latchininsky, “Grasshopper outbreak challenges conser- vation status of a small Hawaiian Island,” Journal of Insect Conservation, vol. 12, no. 3-4, pp. 343-357, 2008. [12] M. J. Samways, “Can locust control be compatible with con- serving biodiversity?” in Grasshoppers and Grassland Health. Managing Grasshopper Outbreaks without Risking Environ- mental Disaster, J. A. Lockwood, A. V. Latchininsky, and M. G. Sergeev, Eds., pp. 173-180, Kluwer Academic Publishers, Dordrecht, Netherlands, 2000. [13] J. Buhl, D. J. T. Sumpter, I. D. Couzin et al., “From disorder to order in marching locusts,” Science, vol. 312, no. 5778, pp. 1402-1406, 2006. [14] M. L. Anstey, S. M. Rogers, S. R. Ott, M. Burrows, and S. I. Simpson, “Serotonin mediates behavioral gregarization underlying swarm formation in desert locusts,” Science, vol. 323, no. 5914, pp. 627-630, 2009. [15] D. A. Cullen, G. A. Sword, T. Dodgson, and S. J. Simpson, “Behavioural phase change in the Australian plague locust, Chortoicetes terminifera, is triggered by tactile stimulation of the antennae,” Journal of bisect Physiology, vol. 56, no. 8, pp. 937-942,2010. [16] M. P. Pener and S. J. Simpson, “Locust phase polyphenism: an update,” Advances in Insect Physiology, vol. 36, pp. 1-272, 2009. [17] M. J. Samways and J. A. Lockwood, “Orthoptera conservation: pests and paradoxes,” Journal of Insect Conservation, vol. 2, no. 3-4, pp. 143-149, 1998. [18] M. G. Sergeev, “Conservation of orthopteran biological diver- sity relative to landscape change in temperate Eurasia,” Journal of Insect Conservation, vol. 2, no. 3-4, pp. 247-252, 1998. [19] A. Foucart and M. Lecoq, “Major threats to a protected grasshopper, Prionotropis hystrix rhodanica (Orthoptera, Pam- phagidae, Akicerinae), endemic to southern France,” Journal of Insect Conservation, vol. 2, no. 3-4, pp. 187-193, 1998. [20] A. V. Latchininsky, “Moroccan locust Dociostaurus maroccanus (Thunberg, 1815): a faunistic rarity or an important economic pest?” Journal of Insect Conservation, vol. 2, no. 3-4, pp. 167- 178, 1998. [21] M. G. Sergeev, O. V. Denisova, and I. A. Vanjkova, “How do spatial population structures affect acridid management?” in Grasshoppers and Grassland Health. Managing Grasshopper Outbreaks without Risking Environmental Disaster, J. A. Lock- wood, A. V. Latchininsky, and M. G. Sergeev, Eds., pp. 71-88, Kluwer Academic Publishers, Dordrecht, Netherlands, 2000. [22] M. J. Samways and M. G. Sergeev, “Orthoptera and landscape change,” in The Bionomics of Grasshoppers, Katydids and Their Kin, S. K. Gangwere, M. C. Muralirangan, and M. Muralirangan, Eds., pp. 147-162, CAB International, Oxon, UK, 1997. [23] M. G. Sergeev, “La secheresse et les schemas de distribution des criquets en Asie centrale et septentrionale,” Secheresse, vol. 7, no. 2, pp. 129-132, 1996. [24] J. A. Lockwood and M. G. Sergeev, “Comparative biogeog- raphy of grasshoppers (Orthoptera: Acrididae) in North America and Siberia: applications to the conservation of biodiversity,” Journal of Insect Conservation, vol. 4, no. 3, pp. 161-172,2000. [25] R. Peveling, “Environmental conservation and locust control — possible conflicts and solutions,” Journal of Orthop- tera Research, vol. 10, no. 2, pp. 171-187, 2001. [26] B. P. Uvarov, Grasshoppers and Locusts, vol. 2, Centre for Overseas Pest Research, London, UK, 1977. [27] D. Otte, The North American Grasshoppers — vol. 1. Acrididae: Gomphocerinae and Acridinae, Harvard University Press, Cambridge, Miss, USA, 1981. 4 Psyche [28] M. G. Sergeev, Principles of Orthopteroid Insects Distribution in North Asia, Nauka Publishers, Novosibirsk, Russia, 1986. [29] K. A. Vandyke, A. V. Latchininsky, and S. P. Schell, ‘Importance of ecological scale in Montane Grasshopper (Orthoptera: Acrididae) species structure in similar habitat between differ- ing soil textures and dominant vegetative canopy coverage,” Journal of Orthoptera Research, vol. 18, no. 2, pp. 215-223, 2009. [30] M. G. Sergeev, “Ecogeographical distribution of Orthoptera,” in The Bionomics of Grasshoppers, Katydids and Their Kin, S. K. Gangwere, M. C. Muralirangan, and M. Muralirangan, Eds., pp. 129-146, CAB International, Oxon, UK, 1997. Hindawi Publishing Corporation Psyche Volume 2011, Article ID 157149, 8 pages doi: 10. 1155/201 1/157149 Research Article Observations on Forced Colony Emigration in Parachartergus fraternus (Hymenoptera: Vespidae: Epiponini): New Nest Site Marked with Sprayed Venom Sidnei Mateus Departamento de Biologia, Faculdade de Filosofia Ciencias e Letras de Ribeirdo Preto, Universidade de Sdo Paulo, Avenida Bandeirantes 3900, 14040-901 Ribeirdo Preto, SP, Brazil Correspondence should be addressed to Sidnei Mateus, sidneim@ffclrp.usp.br Received 8 September 2010; Revised 20 December 2010; Accepted 12 February 2011 Academic Editor: Robert Matthews Copyright © 2011 Sidnei Mateus. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Five cases of colony emigration induced by removal of nest envelope and combs and a single one by manipulation are described. The disturbance was followed by defensive patterns, buzz running, and adult dispersion. An odor trail created by abdomen dragging, probably depositing venom or Dufour’s gland secretions, connected the original nest to the newly selected nesting place and guided the emigration. The substrate of the selected nesting place is intensely sprayed with venom prior to emigration, and this chemical cue marked the emigration end point. The colony moves to the new site in a diffuse cloud with no temporary clusters formed along the odor trail. At the original nest, scouts performed rapid gaster dragging and intense mouth contacts stimulating inactive individuals to depart. Males were unable to follow the swarm. Individual scouts switched between different behavioral tasks before and after colony emigration. Pulp collected from the old nest was reused at the new nest site. 1. Introduction According to Sonnentag and Jeanne [1], three organizational challenges must be faced when swarms disperse. The first is that a subset of the population, the scouts, must find and agree upon a suitable nest site. Second, the scouts induce the rest of the colony to leave for the new site. Finally, scouts guide the emigrating swarm to the new site. A division of labor during the swarming and new nest initiation also has been described [1-4]. West-Eberhard [5] described, for Epiponini, a pattern of aggregation called clumped swarms. These consist of temporary, compact clusters formed at intervals along the swarming route while searching for potential nesting sites. Clumped swarms have been described for Polybia ignobilis, P. raui, P. occidentalis , and Parachartergus apicalis [6]. According to Hunt et al. [7], Apoica pallens also forms temporary clusters during its emigration. Scent marking behavior is of great importance to signal the route followed by swarms. Jeanne [8, 9] experimentally confirmed NaumamTs conclusion [10] that swarming wasps follow a scent trail made by secretions of abdominal glands applied to surfaces. According to Howard et al. [11], Apoica pallens individuals were observed flexing their terminal gaster segments dorsally while clustering in leaves during an absconding event. This posture exposed the bases of the 5th and 6th sternites, suggesting that the wasps were releasing a pheromone from the sternal glands on these segments. In this way, they would communicate via aerial signaling, rather than by gaster dragging on substrate. Smith et al. [12] suggested that wasps use diverse pheromones to coordinate the swarm. Although gland identity has not been confirmed for most cases, it seems safe to conclude that the gastral ones are often involved. Several Neotropical genera of epiponines, including Parachartergus, lack Richard’s gland, and some lack the van der Vecht’s gland as well [12]. In several species of these genera, scouts still display the gastral rubbing and trail- following behavior. Sternal glands are also absent in the Paleotropical genus Polybioides. However, these wasps use Dufour’s ( Po . tabidus) and the venom gland ( Po . raphigastra ) as sources of trail pheromone [ 12-14] . 2 Psyche Here, for the first time, the behavior of Pa. fraternus scouts during forced emigration is described. I show that Pa. fraternus wasps spray venom on the substrate of the newly selected nesting site prior to emigration. Individual behavioral flexibility displayed by scout wasps during the emigration process is also described. 2. Material and Methods I observed six swarming events in colonies of Pa. fraternus over four years (2001-2004) during the months of February to June. Four colonies (Cl, C2, C3, and C4) were studied on a private property at Pedregulho, Sao Paulo State (20°15'S 47°27'W). Two colonies (C5 and C6) were relocated from the same municipality to the University of Sao Paulo, at Ribeirao Preto Campus. The relocations occurred after sunset to ensure that all adult wasps remained inside the nest. Five colonies were induced to emigrate by removing their envelope and combs (Cl, C2, C3, C4, and C6). Workers and queens were individually marked with different color dots on the thorax. While the majority of the individuals were color- coded at the original nest, some scouts were marked while walking at the new nest site, and others were collected and coded while gaster dragging in leaves nearby. Queens were recognized by their characteristic behav- ioral syndrome, in which their movement on the substrate was slower than workers, their wings were always half- opened, and the gaster was curved laterally (about 30 degrees) towards every approaching wasp (similar to the gaster-bending display of Metapolybia queens mentioned by West-Eberhard [15]). Queen status was confirmed through oviposition observations in the new nest site after colony establishment. Individual wasps observed dragging their abdomens at the original nest substrate, on leaves or prominent objects on the chemical trail or dragging and venom spraying at the new nest site, were considered to be scouts. A total of 1 1, 10, 29, 15, 10, and 12 queens were color- coded in Cl, C2, C3, C4, C5, and C6, respectively. For the workers, 38, 51, 40, 36, 198, and 37 individuals were marked for each colony, respectively. Relative age and ovary development data were taken for individual wasps only from colony C3. For this, a haphazard sample of color- coded workers was collected after emigration, while laying an egg, or directly from inside the nest when they arrived carrying pulp or water. Relative age was estimated by the extent of pigmentation of the transverse apodeme across the hidden base of each sternite. In this way, following Richards [16], West-Eberhard [17], Forsyth [3], and Mateus et al. [18], females were assigned to the following progressively older age classes: (1) no pigmentation; (2) light brown; (3) dark brown; (4) black. Pattern of ovarian development was checked only for scouts on this colony. Scouts ovaries were categorized into five developmental types following the methods described by Mateus et al. [ 18] . Type 1 consisted of filamentous ovarioles bearing no visible oocytes. Type 2 possessed slightly developed oocytes, while type 3 consisted of small well-defined oocytes. Type 4 were those with at least one near- mature oocyte, while type 5 possessed one or more well-developed oocytes. Except for colony 5, which had been observed and video- taped before the pre-emigration process, all colonies were periodically videotaped beginning from the time envelope and combs were removed until nest re-establishment at the new nest site. Chemical trail deposition and the process of a new nest site selection by scouts was observed and recorded. At the new site, scouts were also periodically videotaped. On the day after the nest structure removal, a video record of the wasps clustered on the original nest substrate was used to estimate the population for each colony. The cluster was recorded early in the morning (i.e., about 07:00) before the wasps started flying. Swarming behavior comprises the entire sequence of events from removal of the nest structures up to new nest site settlement. Pre -emigration period was measured as the time between removing the nest structures and the start of the emigration process. The start point of the emigration process was considered to be when large numbers of wasps started to fly around the original nest and then departed. Foragers from colony C5 were color-coded and its observations in the video tape showed that returns to the nest with clearly distended abdomens and in general exchanging the liquid at the nest entrance referred to water foraging; while foragers presenting abdomens near to the normal size, exchanging the resources inside the nest, and spending long time outside the nest were supposedly nectar foragers. Prey and pulp could be observed in the foragers mandibles and were clearly distinguished by color and shape. 3. Results 3.1. Chronological Account of the Swarming of Pa. fraternus. Nest envelope and comb removal from five of the six studied colonies (except colony C5), described above, was followed by similar behavior in all studied colonies. Removal of the nest structures provoked aggressive defensive behavior including venom spraying directly into the observer’s eyes through the mesh of the bee-suit veil, buzz running, and dispersion. The buzz running executed by this specie is similar to the one described by Sonnentag and Jeanne [1] for Polybia occidentalism in which the wasp runs rapidly on the surface of the original nest buzzing its wings and performing quick stops followed by another running event. Many of the disturbed wasps landed on nearby leaves either alone or in small groups. After 20 to 30 minutes, the dispersing individuals returned to the original nest site and crowded on the remaining nest substrate fiber. As soon as the returning wasps landed on the substrate, intense buccal and antennal contacts were observed. During and immediately after envelope and comb removals, all six colonies displayed brood cannibalism. Many wasps were observed removing large larvae from cells, chewing them for a while and then dropping them on the comb margin or after carrying them in the mandibles in flight. In colony C5, when the envelope was partially Psyche 3 removed to promote intranest observations, similar brood cannibalism occurred involving medium-sized larvae. During pre-emigration, some individuals were observed dragging their abdomens on the substrate of the original nest before flying. Although the queens and some workers remained inactive, other workers were walking faster than usual. A few foragers returned with water, nectar, or prey and rapidly transferred them to other adults. Some scouts were observed to perform a slow hovering flight while facing the nest 0.3 to 1.0 meters away, followed by landing on the nest substrate or flying away. This type of flight corresponds to that described by West-Eberhard [5] as a looping flight, and it will be subsequently referred to this way. Upon landing, scouts often antennated the substrate while walking. Scout wasps visited leaves, tree trunks, fence posts, walls, and prominent objects in different directions within 50 meters from the nest. As the looping flights activity increased, some scouts started gaster- dragging runs, which consisted of rapid walking shaking its abdomen side to side with the gastral sternites pressed and rubbed against the substrate. Dragging runs are typically fast and followed by flights. Scout wasps continually returned to the original nest where they landed on the substrate walking faster than usual, making many buccal contacts which were followed by dragging and a new flight event. Over time, scout numbers gradually increased. The increase in the number of scout wasps could clearly seem in the video record of the individuals on the leaves and other marked places along the chemical trail. At the end of the day, the individuals returned to the original nest site and formed 3 to 5 overnight resting clusters separated by 5 to 10 cm. The next morning, scouts began flying soon after sunrise, and the number of scouts gradually increased throughout the day. The new nest site was found by following the flight direction of scouts which had been dragging on peripheral leaves and other prominent objects. At the new nest site, groups of individuals were gaster dragging on the surface and performing looping flights in front of the selected place (colonies Cl, C2, and C3). After landing on the new nest site, the scouts usually antennated and pressed their mouth- parts against the substrate while walking. After that, they performed gaster dragging and flight. These behaviors were usually repeated many times by the same individuals and followed the same sequence in every observation (Figure 1). Following the return of the first scouts to the original nest site, many unmarked individuals were observed following the chemical trail, and landing on the new nest site adopting the same behavior described for the scouts. About one hour before the start point of the emigration, additional behavioral changes were observed. On the original nest site, speed and intensity of dragging behavior increased as well as the number of individuals performing these behaviors. Meanwhile, on the new nest site, as observed for colonies Cl, C2, and C3, scouts were performing fast gaster- dragging runs and bending their abdomen downwards, then, after a quick stop, they sprayed venom on the substrate (Figure 2). Close inspection of the videotaped instances revealed extruded stings during venom spraying. No vapor Figure 1: Cluster of scouts of Pa. fraternus from colony C2 visiting a selected new nest site and gaster-dragging on the substrate surface during pre-emigration. Figure 2: Scouts of Pa. fraternus from colony C2 spraying venom on the substrate at the new nest site prior to population departure from the original nest. clouds were observed after this venom spraying, nor could liquids be found on the substrate although an intense smell of venom was perceivable, and it was enough to cause allergic reactions in the eyes and nose of the observer. Trail followers arrived at the new nest site in a diffuse cloud, and they flew in wide looping arcs before landing. Early in the new nest initiation phase, a circle of individuals formed surrounding the area containing queens and inactive wasps and where the new nest structures were being built. A few males were counted (6, 4, 5, 9) on the substrate of the original nests after population departure in colonies C2, C3, C4, and C6, respectively. No males were found at the new nest site. 3.2. Individual Colony Emigration Details (Table 1 ). In colony Cl, one hour before departure, 22 scouts were present at the new nest site, dragging and spraying venom. About 20 minutes before the beginning of the emigration process, the population size in the original nest was estimated to be 280 wasps. Emigration itself was characterized by a high number of wasps leaving the original nest and following the chemical trail made by scouts. Several wasps hovered in 4 Psyche Table 1: Data relating to emigration events for the six colonies of Parachartergus fraternus studied in Brazil. See text for additional details. Colony number Pre-emigration initiation (date and time) Pre-emigration duration (hours) Cluster of scouts found prior to emigration Duration of emigration (minutes) Date and time of emigration Emigration distances (meters) Population estimate Cl 02/25/01 10:35 50 02/26/01 15:00 12 scouts 30 02/27/01 11:30 28 290 C2 03/22/01 9:00 74.5 03/25/01 10:00 24 scouts 25 03/25/01 11:30 30 270 C3 03/03/03 11:30 48 03/05/03 11:00 40 scouts 35 03/05/03 11:23 28 350 C4 03/03/03 14:30 49 not found not observed 03/05/03 between 12:15-13:35 75 360 C5 06/14/03 8:00 55 not found 25 06/16/03 15:00 26 340 C6 03/23/04 18:30 67 not found not observed 03/26/04 between 12:50-13:45 33 320 front of the scent-marked leaves or landed on them, often antennating the substrate while walking. One hour after the start of the emigration process, 260 individuals were estimated in the new site area. Some scouts continued gaster dragging and spraying venom on the substrate at this point. Emigrating wasps landed on the place where scouts had sprayed venom. After most wasps reached the new nesting place, some color-coded scouts returned to the original nest using the chemical trail and stimulated the remaining wasps to leave through buccal contacts and gaster dragging. Some marked wasps were observed to collect pulp from the original nest before and after emigration. The whole emigration event lasted about 30 minutes. In colony C2, one hour before emigration, 24 scouts wasps were counted gaster dragging and spraying venom on the new nest site substrate. Four minutes before the beginning of population departure, one scout landed in the new site with a small pulp ball in its mandibles. Two minutes after the emigration started, 73 individuals were estimated at the new nest site and, after ten minutes, about 100 individuals could be found there. The large number of wasps spraying venom in the substrate produced a strong smell of venom around the new nest site. The first peduncle construction started 36 minutes after the emigration process had begun. Some wasps were observed returning to the original nest to collect vegetal pulp. A cluster of scouts from colony C3 followed the same behavior pattern mentioned above. The number of scouts at the new site and alighting on the chemical trail gradually increased. At the beginning of the emigration process, about 30 wasps were flying around the new site, and 108 individuals were estimated at the original nest site. Just prior to the start of the emigration, some wasps shared pulp at the new nest site, and two peduncles were initiated almost simultaneously. Wasps also were observed returning to the natal nest to collect pulp. The duration of migration in colony C3 was around 35 minutes. In colony C4 , two hours before emigration, 24 scout wasps were observed in a house wall 22 meters from the natal nest; they were gaster dragging on the substrate. About the same time, another group of scout wasps was observed following a chemical trail tracking in a different direction. In the natal nest, the population was agitated, buccal contact was frequent, and arriving scouts performed gaster dragging and flew away almost immediately. The number of scouts in the wall cluster gradually decreased over the next two hours. Unfortunately, the spot selected for the new site could not be found before the emigration. Again, many scouts returned to the natal nest and collected pulp. On the day after, we found the new nest site 75 meters from the natal nest. Four small combs and a partial envelope had already been built. Colony C5 wasps were observed after the repeated envelope removals over the days prior to emigration. Striking behavioral changes occurred, including a notable reduction in foraging activity, with most of the adult population remaining inside without any external activity. Part of the envelope previously removed to enhance inner observations (see Section 2) was not reconstructed, and a few large larvae were dropped from the colony entrance. Scout wasps were seen visiting leaves 40 meters from the original nest, and thereafter, their activity increased. Some scouts were performing gaster dragging and hasty running over leaves nearby, while others executed the same dragging on the nest entrance before departure. The pre-emigration pattern for this colony was similar to the ones observed for the other colonies in which the nest structures were actively removed. All queens remained inside the nest, mostly hidden below the combs. During the second and third day, the number of scout wasps increased on the chemical trail. Some marked wasps started to display Psyche 5 Table 2: Examples of different behavioral roles displayed by selected individual scouts of Pa. fraternus from colony C5 which were the most active foragers and scouts during pre-emigration and nest initiation. Previous role, forager activity: Fn = forager nectar; Fw = forager water, Fpr = forager prey; Fpu = forager pulp. During pre-emigration, individual number of gaster- dragging events on the substrate near natal nest entrance, and number of trips to the new nest site. Nest initiation, forager activity, and number of trips per individual. Individual Previous role During pre-emigration Nest initiation Forager activity Number of gaster draggings Forager activity and number of Number of trips and number of trips observed trips observed 1 Fn-1 2 2 Fpu-6 2 Fn-5 4 5 3 Fn-1 11 14 Fpu-3 4 Fn-2 2 6 Fpu-5 5 Fn-5 1 1 6 Fn-4 3 10 Fpu-1 7 Fn-9 2 6 Fpu -1 8 Fw-2 2 13 Fpu-2 9 Fpr- 8 1 4 Fpu-2 10 Fpu-1 1 5 11 Fw-5 2 10 Fpu-5 12 Fn-2 1 13 Fpu-4 13 Fn-5 3 10 Fpu-5 14 Fn-1 1 2 15 Fn-1 2 2 16 Fn-1 6 4 Fpu-1 scout behavioral patterns. The number of wasps in the nest entrance increased as the number of wasps gaster dragging on the substrate in front of the nest entrance increased. Emigration was initiated after a large number of wasps started leaving the original nest and flying around. A diffuse but continuous movement of wasps formed a “cloud” 2 to 4 meters wide and 3 meters high until reaching the new nest site. At the new nest site, scouts continued gaster dragging and spraying venom on the substrate throughout the swarm movement and even after the population arrived at the new nest site. At the end of the chemical trail, a great number of wasps performed looping flights around the new site before landing on it. Nest construction started almost immediately after population arrival, with a comb peduncle and a piece of envelope being built simultaneously. Foraging activity for pulp and water increased, and many wasps returned to the original site to collect nest material. In colony C6, two hours before emigration, a large number of scouts were flying around the original nest and landing on leaves nearby. Individual scout behaviors were similar to others mentioned above. Emigration start point was not recorded; however, the duration of pre-emigration was about 67 hours. The new nest was found the next day, 33 meters from the original one, and 12 meters high. 3.3. Individual Task Flexibility of Scout Wasps. Patterns of scout wasp behaviors for the six observed colonies were similar. During nest initiation, color-coded scouts from colonies Cl and C2 built cells, shared pulp, and foraged for water and pulp. In the day following colony initiation, marked scouts were the most active builders and foragers. In colony C3, before emigration, a scout removed pulp from the substrate in the natal nest. At the new nest site, two scouts shared pulp and applied it to an initial peduncle. During nest initiation, scouts were active builders and foraged for water. A single color- coded scout was captured immediately after laying an egg in one of the first cells built in the new nest on 03/05/03. Dissection revealed it had devel- oped ovaries and was uninseminated. However, none of 26 marked scouts collected on the following day while returning with water, pulp, or while building envelope or cells, were young individuals or had any ovarian development [18]. In colony C5, we verified that some active foragers became active scouts during pre-emigration. Although the cluster at the new nest site was not found before the emigration event, behavioral patterns during nest establishment were observed. Table 2 summarizes the division of labor among color-coded individuals whose behaviors were previously videotaped during a study aiming to analyze foraging activi- ties, and behaviors during the worker production phase, pre- emigration, and nest initiation processes. Color-coded scouts observed gaster dragging on the substrate in front of the natal nest entrance were subsequently monitored, revealing individual task flexibility and division of labor, as these same individuals had been observed foraging for water, nectar, pulp, and prey before pre-emigration. Remarkably, during the pre-emigration phase, they turned into active scouts, depositing the chemical trail and stimulating the inactive population to emigrate. During the new nest initiation, these same wasps foraged for pulp and shared it with nest- mates. 6 Psyche 4. Discussion Venom spraying to mark the new nest site prior to colony emigration has not been reported for any other epiponine species. For Pa. fraternus , venom spraying was previously described exclusively as having a defensive function [19, 20], also observed for other species in the genus, Pa. aztecus [21] and Pa. colobopterus [20]. The results of the induced swarming showed that the duration of the pre-emigration stage varied from 2 to 3 days in Pa. fraternus (Table 1). This duration is similar to that described for Agelaia areata [22] but was longer than that described for P. occidentalis [6]. According to Jeanne [22], the pre-emigration phase of an absconding swarm of Agelaia areata lasted about 4 days. Bouwma et al. [6] induced colonies of P. occidentalis to emigrate by dismantling their nests; the swarming process occurred on the same day for eight colonies and on the next day for one other experimental colony. However, for both species, the pre- emigration period was not precisely determined since it was not the main objective of those investigations. The results described here also differ somewhat from other studies [1, 5, 6, 11], probably due to methodological differences in swarm triggering (e.g., entire nest translocation [1, 6, 9] or natural swarm observations [5, 22]). The duration of the pre-emigration phase suggests that adults of Pa. fraternus were not prepared for the obligatory departure. For Pa. fraternus, in all cases, after the disturbance associated with the nest structures removal, the colony population gradually returned to the original nest site and regrouped on the substrate covered by the remaining pulp fibers that defined the natal nest. No temporary clusters of wasps were observed to form along the emigration route. In studies of P. occidentalis, when a swarm was induced, scouts typically formed small aggregations near the old nest along the eventual emigration trail being marked [ 1, 6, 23] . Chadab [24] observed regrouping off the nest in various Neotropical epiponine species attacked by army ants. Howard et al. [11] observed regrouping in Apoica pollens following absconding. After a failed attempt to collect the entire population of a nest of A. thoracica, all individuals left the nest and regrouped in a bush four meters from the original nest (S. Mateus unpublished observation). Immediately after the removal of nest structures, buzzing runs or breaking behavior were displayed by many individu- als in the substrate of the original nest. This behavioral pat- tern was similar to one described by Sonnentag and Jeanne [1], who noted that wing buzzing may be associated with pheromone release and dispersion. Excited buzz running by a few or many individuals is the most characteristic behavioral response observed when absconding is provoked by a sudden event [5, 8, 10, 23]. Ezenwa et al. [25] suggest that buzz running is a pre-emigration behavior, associated with brood removal and occasional cannibalism. The observed brood cannibalism during envelope removal in this study was similar to that reported for Metapolybia aztecoides, Protopolybia acutiscutis, and Synoeca surinama [5]. Disturbed colonies of Chartergellus communis and Pa. smithii displayed similar behavior (S. Mateus unpub- lished observation). “Dragging behavior” for trail marking, as well as repeat- edly rubbing the ventral surface of the gaster on substrates between new and old nest sites, was first reported by Naumann [10] and since observed in many species of swarm- founding wasps [3, 5, 9, 12, 26]. Gaster-dragging behavior was previously observed in Pa. fraternus [12, 26] both before and during emigration. The observations of scouts of Pa. fraternus marking the chemical trail by dragging their abdomens on leaves or other prominent objects along the emigration route suggest that the wasps may use venom or possibly products from the Dufour’s gland as sources of trail pheromone since Richard’s Gland is absent in this species. This secretion would be spread on surfaces by the gaster-dragging behavior. The African ropalidiine Polybioides tabidus also lacks sternal glands, and Francescato et al. [13, 14] suggest that in this species, the trail pheromone is produced in the Dufour’s gland. Consistent with studies on some other epiponine species (e.g., P. occidentalis ) [6], we found that Pa. fraternus males were not able to follow the emigration swarm, as they remained on the substrate of the original nest after all the females had emigrated. However, Apoica males can follow the swarm [11, 19, 27], Males have also been observed in emigrating populations of Apoica thoracica and Synoeca virginea (S. Mateus unpublished observations). Colony C5 was under observation for other purposes when its spontaneous swarming took place. Similar to other epiponine species [3, 5, 25], the first signs suggesting imminent nest abandonment were buzz running and a reduction of foraging and building activities. During pre- emigration, no group or clusters of wasps were present on the nest envelope. However, many indi- viduals stayed around the nest entrance performing intense buccal contacts with incoming scouts. Following site selection and spray marking, many scouts returned to the natal nest where they performed gaster dragging and intense buccal contacts with inactive wasps before returning to the new nest site. According to Son- nentag and Jeanne [1], the increased bumping stimulates previously inactive individuals to become active and follow the pheromone trail to the new nest site. After contact interactions with scouts, the previously inactive individuals gradually started flying around the natal nest, and within a few minutes, most departed. West-Eberhard [5] reports similar observations. Reuse of pulp from original nest in early stages of new nest establishment was observed in all colonies and has also been previously reported by O. W. Richards and M. J. Richards [28] and Sarmiento-M [29] for Pa. fraternus. In one case (colony C3), construction of the new nest began before the swarm arrived. Nest initiation prior to emigration has also been observed in P. velutina [24], P. sericea [9], and Apoica pollens [10]. During the new nest initiation, a group of wasps encir- cled the selected nesting spot, facing outward, apparently defending the site. Queens and many inactive wasps clustered Psyche 7 in the upper part of the circled area. Forsyth [3] estimated that about 80 percent of a swarm’s population serve as guards, while the remainder become actively engaged in foraging and building activities. Pa. fraternus queens’ only observed activity was oviposi- tion in cells newly built by workers. According to Herman et al. [30], queens of Pa. colobopterus are rarely involved in any interactions with other colony members, and no evidence that queens regulate worker activity was found. For reproductive swarms of epiponine wasps, distances from the natal to the new nest are difficult to obtain. However, absconding swarms typically re-establish the new nest within a few meters of an abandoned site [5, 6, 31] (but an absconding swarm of Agelaia areata traveled 319 meters over four days [22] ). For the six studied colonies of Pa. frater- nus, average emigration distance was 36.16 meters (Table 1). For six emigrating colonies of P. sericea, the new nest was located 15 to 172 m (mean = 85 meters) from the natal nest [9]. According to Bouwma et al. [6], the distance for 102 induced swarms of P. occidentalis colonies ranged from zero to 115 meters. Forsyth [23] suggested that the upper limit for emigration distance might be the foraging range of the foragers who act as scouts. For reproductive swarms, the dispersal distance is important since it potentially affects population “viscosity” and inbreeding. In addition, distance of swarm dispersal can potentially impact competition for resources between the parent and daughter colonies [3]. Division of labor is the division of the work force among the range of tasks performed in the colony, whereas task partitioning is the splitting of a discrete task among workers [32, 33]. For Pa. fraternus, both were observed at different phases of the emigration event — during pre-emigration, emigration, and nest initiation. Scouts selected the new nest site, deposited the chemical trail, and stimulated inactive nest mates to leave. At the new nest site, some marked wasps switched to become active builders and foragers. Flexible behavior was striking in colony C3, where one scout was first observed building cells and then ovipositing during nest initiation. Dissection confirmed that this individual fit the definition of an “intermediate” worker, which O. W. Richards and M. J. Richards [34] refer to as an uninseminated female bearing some kind of ovary development. Such individuals are commonly found in nests of Pa. fraternus [18, 19], where their abundance varies at different stages of the colony life cycle. 4.1. How Do the Emigrating Wasps of Pa. fraternus Recognize the End of the Chemical Trail? According to Jeanne [9], for P. sericea, the new nest site is recognizable by the presence of a large number of gaster-dragging wasps. In P. occidentalis, in which temporary clusters are formed along the emigration trail, the clusters may serve as visual cues to attract the emigrating wasps [3]. The population ultimately aggregates on the last cluster, probably attracted by pheromone release [11]. A remarkable finding in this study is that Pa. fraternus does not form clusters along the emigration route. Instead, emigrating wasps form a diffuse swarm, and since scout wasps abundantly spray venom on the substrate of the new nest site, the venom could be the cue that indicates the end point of the chemical trail. This hypothesis is also supported by the fact that no venom spraying has been observed while scouts were marking the chemical trail, occurring only at the end point. Additionally, the strong venom concentration at the new nest site could serve to deter potential enemies, such as ants, at a vulnerable stage of the nesting cycle. Acknowledgments The author acknowledges the following: financial support by FAPESP, CNPq, and Biology Department of FFCLRP- USP. He thanks Ronaldo Zucchi and Fabio S. Nascimento for reading the paper; Sonia, Veronica, and Lucas Mateus for fieldwork company; Tulio Nunes and Larissa G. Elias for the help with manuscript corrections and text improvements; Regis Giolo and his family, Jose Valentin Bordini, and all friends who live in the Furna Sao Pedro in Pedregulho Sao Paulo State for permissions. Finally, the author is grateful to the journal editor and the three reviewers for their valuable comments. References [1] P. J. Sonnentag and R. L. Jeanne, “Initiation of absconding- swarm emigration in the social wasp Polybia occidentalism Journal of Insect Science, vol. 9, article 11, 2009. [2] R. L. Jeanne, “The swarm-founding Polistinae,” in The Social Biology of Wasps, K. G. Ross and R. W. Matthews, Eds., pp. 191-131, Cornell University Press, Ithaca, NY, USA, 1991. [3] A. B. 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Richards, “Observations on the social wasps of South America (Hymenoptera, Vespidae),” Transactions of the Royal Entomological Society of London, vol. 102, pp. 1-170, 1951. Hindawi Publishing Corporation Psyche Volume 2011, Article ID 861747, 8 pages doi: 10. 11 55/20 11/861 747 Research Article Diversity of Social Wasps on Semideciduous Seasonal Forest Fragments with Different Surrounding Matrix in Brazil Getulio Minoru Tanaka Junior 1,2 and Fernando Barbosa Noll 1 1 Laboratorio de Vespas Socials, Departamento deZoologia e Bo tdnica, IBILCE-UNESP, Rua Cristovao Colombo, 2265 CEP 15054-000 Sdo Jose do Rio Preto-SP, Brazil 2 Departamento deBiologia, FFCLRP-USP, Avenida Bandeirantes, 3900 CEP 14040-901 Ribeirao Preto-SP, Brazil Correspondence should be addressed to Getulio Minoru Tanaka Junior, gtanaka@gmail.com Received 17 December 2010; Accepted 15 February 2011 Academic Editor: Abraham Hefetz Copyright © 2011 G. M. Tanaka Junior and F. B. Noll. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. We surveyed social wasps (Polistinae) present in forest fragments of northwest of Sao Paulo state with different surroundings composed of a matrix of citrus crops and sugarcane in the expectation that the former matrix would be more diverse than the latter. We collected specimens actively using attractive liquids. We obtained 20 species in Magda, 13 in Bebedouro, 13 in Matao, and 19 in Barretos. The most common genus was Agelaia in all of the areas. The greatest Shannon-Wiener index of diversity was obtained in Magda (FL = 2.12). Species such as Brachygastra moebiana, Metapolybia docilis, Mischocyttarus ignotus, M. paulistanus and M. consimilis had not been recorded on recent surveys in the state. Furthermore M. consimilis is a new record for the state. We concluded that, with our data, a relation between the occurrence of social wasps and the surrounding matrix was not detected. 1. Introduction Forest fragments may be treated as islands, and the sur- rounding area, the matrix, is treated as an ocean. The matrix area is considered to be ecologically uniform, exerting little influence on populations inside the fragments [1, 2]. More recently, some studies have demonstrated that the surround- ing matrix can exert neutral, positive, or negative influences on the populations [3-5] . The replacement of natural areas by monocultures and pastures is one of the main causes of reduction of local and global diversity [6]. Besides habitat fragmentation, the use of pesticides and insecticides reduces the diversity of pollinators [7]. Flowever, Durigan et al. [8] state that some crops have less impact on the natural vegetation than cattle. The majority of crops depend on or benefit from, the action of pollinators [9]. Pimentel et al. [10] show a great richness of arthropod species on many crops. Survey works are important because the survey of species in an area is the first step to its conservation and rational use. Without the knowledge of what species are present in an area, it is very difficult to take action aimed at conservation [11]. Pimentel et al. [10] assert that, as important as it is to conserve the biodiversity of national parks, it is important to conserve biological diversity in agricultural ecosystems, which, to- gether with human settlements, cover approximately 95% of terrestrial environment [12]. Two of the most important monocultures in Sao Paulo state are sugarcane ( Saccharum spp) and citrus ( Citrus spp). Sugarcane is the main crop of Sao Paulo state with about 5.5 million hectares in 2007/2008 [13]. Regular use of burning facilitates manual harvest and repels venomous animals [ 14] , but causes serious damage to the ecosystem [15] while the use of fertilizers may pollute watercourses and cause salinization of the soil [16]. Organic fertilization systems that can shelter a great biodiversity have been recommended [17]. Brazil is the world’s greatest producer of oranges with about 18.5 million tons, and Sao Paulo State contributes about 15 million tons [18], grown on about 750 thousand hectares in 2007/2008 [13]. During the bloom, oranges offer a great production of pollen and nectar that can attract pollinators [19]. It would be useful to know if a survey of insects at a high trophic level reflects the matrix nearby with respect to the sterility (or toxicity) of some crops, 2 Psyche such as sugarcane, and the productivity of others, such as oranges. There are few data comparing areas with these two sur- rounding matrices and their possible effects to the biota. Rinaldi et al. [20] found a surprisingly high richness of spi- ders on sugarcane plantations. Ott et al. [21] sampled spiders on herbaceous vegetation in two different citrus orchards, “traditional” and “ecological,” and despite the differences in cultivation practices, they found a lower richness than Rinaldi et al. [20]. Ott et al. [21] also did a survey on citrus trees of the “ecological” orchard, and there they found a greater richness of spiders species than Rinaldi et al. [20]. Andena et al. [22] did a survey of bees on an area that was previously surveyed by Campos [23] and found a lower rich- ness of species. There were some changes in the surrounding matrix due to the replacement of the natural vegetation by sugarcane crops and pasture. The most common pollinator of Citrus in Brazil is Apis mellifera, but Tetragonisca angustula and Trigona spinipes are also frequent floral visitors [24, 25]. Other Hymenoptera and some Coleoptera, Diptera, Lepidoptera and Neuroptera also are floral visitors of Citrus [25]. A study in Rio Grande do Sul state observed five orders of predatory insects (Coleoptera, Hymenoptera, Neuroptera, Thysanoptera and Hemiptera) in canopies of C. deliciosa under organic management [26]. Social wasps have little importance with respect to pol- lination, but they are frequent floral visitors. Some of them collect nectar for colony’s energy supply [27]. These insects show great ability to forage and collect other materials they need such as water, carbohydrates, prey and pulp [28-30], and are being used to control some pests [31]. After Richards [32], many surveying works have been done in different areas in Brazil using various methodologies [11, 33-55]. Here we compare four fragments of semideciduous seasonal forest of northwest of Sao Paulo state with a surrounding matrix composed of crops of citrus or sugarcane. Moreover, we compare those results to other surveys done in the same region. 2. Material and Methods 2.1. Study Area. Northwest of Sao Paulo state is the most deforested area of the state and with the lowest concentration of conservation units [56]. The natural vegetation of the region is characterized as semideciduous seasonal forest and cerrado (orbrazilian savanna). The study was conducted on fragments from the munici- palities of Magda (20°30 / S 50° 13' W, 1656.20 ha), Bebedou- ro (20°53 / S 48°32' W, 393.94 ha), Matao (21°37' S 48°32' W, 2189.58 ha) and Barretos (20°29' S 48°49' W, 597.33 ha). The first two had sugarcane crops as the surrounding matrix and the last two had citrus crops as the surrounding matrix. 2.2. Methods. The methodology used was based on active collection using an attractive liquid [57]. This methodology uses a 200 m transect in the vegetation on which is sprayed a solution of sucrose (1:5, commercial sugar: water) with 2 cm 3 of salt for each liter of solution. Using a costal sprayer, Rarefaction curve • Magda ■ Matao A Bebedouro ♦ Barretos Figure 1: Rarefaction curve for the social wasps collected in the four studied areas. Magda • SObs □ ACE A ICE Figure 2: Richness of species observed and estimated using ACE (Abundance-based Coverage Estimator) and ICE (Incidence-based Coverage Estimator) indexes to the area of Magda. about 500 mL of solution was sprayed on each point of col- lection, in an area of approximately 3 m 2 . Ten points were defined, 20 m distant from each other along the transect. The attracted wasps were captured with an entomological net, from 11:00 AM to 3:00 PM, during five minutes at each collecting point, with a spray interval of approximately 1 : 30 h. Collections were made in one transect in the interior of the forest fragment (at least 100 m of the edge), and one at the edge of the forest fragment, near the surrounding matrix. Eight monthly collections were made in Magda (24 h of field work in the interior and 32 h at the edge), ten in Bebedouro (24 h of field work on the interior and 40 h on the edge), seven in Matao (24 h of field work in the interior and 28 h at the edge) and eight in Barretos (28 h of field work in the interior and 32 h at the edge) during the period of December 2007 to December 2009. The specimens collected Psyche 3 Bebedouro • SObs □ ACE A ICE Figure 3: Richness of species observed and estimated using ACE (Abundance-based Coverage Estimator) and ICE (Incidence-based Coverage Estimator) indexes to the area of Bebedouro. Barretos • SObs □ ACE A ICE Figure 5: Richness of species observed and estimated using ACE (Abundance-based Coverage Estimator) and ICE (Incidence-based Coverage Estimator) indexes to the area of Barretos. Matao • SObs □ ACE A ICE Figure 4: Richness of species observed and estimated using ACE (Abundance-based Coverage Estimator) and ICE (Incidence-based Coverage Estimator) indexes to the area of Matao. were identified and deposited in the Hymenoptera Collection at the Department of Zoology and Botany, Sao Paulo state University, Sao Jose do Rio Preto, Sao Paulo, Brazil. 2.3. Statistical Analysis. Shannon-Wiener index of diversity, Berger-Parker index of dominance, Pielou index of evenness, and similarity analysis of Jaccard and Morisita-Horn were done using the software PAST, version 1.37 [58] . ACE (Abun- dance Coverage Estimator) and ICE (Incidence Coverage Estimator) indexes were used to estimate the richness using the software Estimates version 7 [59]. A rarefaction curve model of Hulbert was done on Biodiversity Professional Beta [60]. 3. Results and Discussion Twenty-nine species of social wasps belonging to 10 genera were collected in the four areas of study totalling 1460 indi- viduals (Table 1). Matao was the well-preserved area of study, the largest one, and was surrounded by citrus crops. It was expected to be the richest, but it was the poorest in number of species along with Bebedouro, the poorly preserved site, and it was surrounded by sugarcane crops. Also, Barretos, with a small area and citrus crops on its surrounding, had almost many species as Magda, the second largest area and the fragment that showed the greatest richness of social wasps. In terms of surrounding matrix, it was expected that the fragments located on sugarcane matrix should have lower diversity because of the effects of the fire on the local fauna and the lack of flowers that could attract some wasps (unlike citrus crops), but this was not verified in our work. That null difference between diversity in those surrounding matrices could be supposedly explained by the fast recovery of an area after a burning event (as observed by Araujo et al. [15]) or a possible more intensive use of insecticides on citrus crops [61]. Our collections include species that merit particular notice. We collected species that represent significant records: Brachygastra moebiana, Metapolybia docilis, Mischocyttarus ignotus, M. paulistanus, and M. consimilis had not been recorded by recent surveys in Sao Paulo State; furthermore M. consimilis is a new record to the state. Polybia jurinei was the most abundant species in Magda, Agelaia multipicta was most abundant in Matao, and A. pallipes was most abundant in Bebedouro and Barretos. The genus Agelaia has species 4 Psyche Figure 6: Map showing the localization of the areas of Sao Paulo state where surveys of social wasps were done. Table 1: List of social wasps species collected on the four areas studied. E: edge; I: interior; T: total. Magda and Bebedouro: sugarcane crops Matao and Barretos: citrus crops. Species Magda Bebedouro Areas Matao Barretos E I T E 1 T E I T E 1 T Agelaia multipicta 33 28 61 — — — 45 89 134 — — — Agelaia pallipes 30 29 59 100 161 261 1 — 1 101 94 195 Agelaia vicina 20 25 45 21 44 65 40 18 58 — — — Brachygastra moebiana 4 — 4 — — — — — — 21 — 21 Brachygastra augusti — — — 1 — 1 2 — 2 9 — 9 Brachygastra lecheguana 1 1 2 4 — 4 4 — 4 11 — 11 Brachygastra mouleac 1 — 1 — — — 1 — 1 3 — 3 Mctapolybia docilis 1 — 1 — — — — — — 1 — 1 Mischocyttarus cerberus styx 6 3 9 — — — — — — — — — Mischocyttarus ignotus 2 — 2 — — — — — — — — — Mischocyttarus paulistanus 2 — 2 1 — 1 — — — — — — Mischocyttarus rotundicollis — — — — — — 2 — 2 — — — Mischocyttarus consimilis 1 — 1 — — — — — — — — — Parachartergus smithii 1 — 1 — — — — — — 2 1 3 Polistes simillimus 4 4 8 2 — 2 — — — 8 1 9 Polistes versicolor 3 1 4 — — — 38 2 40 3 1 4 Polistes geminatus — 2 2 — — — — — — — — — Polybia jurinei 40 30 70 — 1 1 2 3 5 20 29 49 Polybia dimidiata — — — 35 21 56 — — — 3 — 3 Polybia fastidiosuscula — — — — — — — — — 6 — 6 Polybia occidentalis 5 1 6 7 — 7 23 — 23 36 3 39 Polybia paulista — — — — — — — — — 22 9 31 Polybia ruficcps xanthops — — — — — — — — — — 4 4 Polybia chrysothorax — — — — — — 14 8 22 — — — Polybia ignobilis 14 3 17 20 6 26 1 — 1 15 8 23 Polybia scricca 3 — 3 2 — 2 — — — 5 — 5 Protonectarina sylveirae — — — 4 — 4 4 — 4 7 — 7 Protopolybia exigua — — — 1 — 1 — — — — — — Synoeca surinama 2 — 2 — — — — — — 9 — 9 Total 173 127 300 198 233 431 177 120 297 282 150 432 Psyche 5 a 3 4-J as X> 5 PQ (in Ph y < P(H h-I a Ph 2 CO 4-> c3 s 3 H- o U o Ph Ph "3 3 Ph z 6 Sh £ i - 0.9 - 0.8 - "H 0.7 H 03 O O >. 0.6 - +-> **H 1 °- 5 1 c/5 0.4 - 0.3 - 0.2 - 0 1.6 3.2 4.8 6.4 9.6 11.2 12.8 14.4 Figure 7: Similarity between the areas of Sao Paulo state where sur- veys of social wasps were done, using Jaccard index. PPta: Patrocinio Paulista, RC: Rio Claro, LA: Luiz Antonio, SRPQ: Santa Rita do Passa Quatro, PF: Paulo de Faria, Pind: Pindorama, NP: Neves Paulista, Turm: Turmalina. 03 PP 3 OS PP 1 0.9 - 0.8 - 0.6 - 0.5 - 0.4 - 0.3 - 0.2 - 0.1 - 0 1.6 3.2 4.8 6.4 8 9.6 11.2 12.8 Figure 8: Similarity between the areas of Sao Paulo state where surveys of social wasps were done, using Morisita-Horn index. PPta: Patrocinio Paulista, Pind: Pindorama, NP: Neves Paulista, Turm: Turmalina, LA: Luiz Antonio, SRPQ: Santa Rita do Passa Quatro, PF: Paulo de Faria. c U 0 x 1 S-H O *Sh 1 7 3h (Ph o Hh 3 o p 20 S. rotermundi ( n = 20) 14 4 2 0 K. resedae (n = 15) 13 2 0 0 were kept together in 70% ethanol within a closed 2mL plastic microcentrifuge tube for two weeks. Five flies were later pulled out and examined under SEM. To simulate contamination via entomological equip- ment, we placed three D. melanogaster for three minutes within an empty 50 mL plastic Corning tube previously used for aspirating a large number of live Alebra sp. leafhoppers. The flies were subsequently examined under SEM. All specimens were sputtered with gold and examined under a Vega 3 Tescan scanning electron microscope. 3. Results On 14 out of 20 S. rotermundi and 13 out of 15 K. resedae individuals, no brochosomes were observed (Table 1). The total of one to two brochosomes per individual were recorded in two K. resedae and three S. rotermundi individuals. In the remaining three S. rotermundi, the total of 7, 14, and 18 brochosomes were found. The largest concentration of brochosomes observed was 12 particles in a 8 X 11 pm field of view (Figure 1(a)). The entire set of 310 micrographs of the two species is available from the author upon request. Both the D. melanogaster flies stored in ethanol together with leafhoppers and those kept in the leafhopper- contaminated aspirator carried individual brochosomes or their groups on various body parts (Figures l(b)-l(d)). 4. Discussion My observations on the two heteropteran species reared in captivity are in stark contrast with the results reported by Wyniger et al. [9]. The majority of individuals had no brochosomes on the examined body parts, and the minority had only a few brochosomes. The discrepancy is particularly striking in the case of S. rotermundi, characterized [9] as the species showing the highest abundance of brochosomes within the investigated Heteroptera and always displaying high number of brochosomes on various body parts, includ- ing the tibiae and tarsal segments. The only explanation consistent with the idea of brochosomes being natural secretory products of Heteroptera [9] would be that the experimental insects did not have enough time to accumulate larger amounts of brochosomes on their integuments during the two weeks after the final moult. Such an explanation is highly unlikely. For comparison, Cicadellidae coat them- selves with brochosomes within hours after the final molt, before they commence feeding [11]. It is much more likely Psyche 3 (c) (d) Figure 1: Insect integuments contaminated with brochosomes. (a) Pulvillus of Sthenarus rotermundi reared in captivity, showing the largest concentration of brochosomes (12 particles) observed among heteropteran specimens in this study and some bacteria, (b) Wing of Drosophila melanogaster kept in ethanol together with leafhoppers; inset: close-up of brochosomes. (c) Eye ofD. melanogaster kept within a leafhopper-contaminated aspirator reservoir, (d) Tarsus of D. melanogaster kept within a leafhopper-contaminated aspirator reservoir. Scale bars: 2 pm (a-d). that the few brochosomes observed in this study were due to a failure to completely prevent contamination. Although direct contact with leafhoppers was precluded, the insects molted in captivity had been in contact with cuttings of host plants growing in the wild, which potentially may have been contaminated by leafhoppers. Remarkably, the specimens that displayed the largest number of brochosomes were also visibly contaminated with other extraneous particles, including bacteria (Figure 1(a)). Therefore, the earlier SEM-based records of brochosomes in Cercopoidea [8], Ffeteroptera [9, 10], and Psylloidea [9] are most likely explained by contamination. The ultrastruc- ture of the Malpighian tubules has not been adequately studied in Heteroptera, while in Psylloidea these organs are either completely reduced or, possibly, transformed into the so-called midgut appendages [12], which have not been studied using electron microscopy. In contrast, the Malpighian tubules of Cercopoidea have been studied at the ultrastructural level in both immatures [13-17] and adults [18] but are not known to produce brochosomes. It is worth noting that all these hemipterans, but particularly cer- copoids, are often collected by the same collectors who collect cicadellids, which increases the probability of contamination. Among multiple potential routes of such contamination, this study has tested and verified the two most obvious ones: via dry surfaces which had been in contact with leafhoppers and via ethanol. The outer integument of most leafhoppers is completely coated with a sheath of brochosomes [5]. These ultramicroscopic particles easily come loose at contact and adhere to foreign surfaces. As a result, sweepnets, aspi- rators, killing jars, forceps, and other entomological tools can become contaminated. The same is possible for plant surfaces where leafhoppers concentrate. Storage of mixed insect samples in ethanol prior to sorting is a common practice. Ethanol does not dissolve or otherwise affect brochosomes, nor it washes most bro- chosomes off the cicadellid integuments. However, some particles come loose and either mix into solution or, possibly, float on its surface, which leads to contamination. Another possible contamination route, which is perhaps less likely but more difficult to exclude, is through the 4 Psyche ambient air, which has been shown to contain significant amounts ofbrochosomes [19]. Finally, perhaps the most intriguing potential route of brochosome contamination is through natural interactions between predators and parasites and their cicadellid prey or hosts, respectively. It is possible that predation may explain the presence ofbrochosomes on at least some of the heteropterans examined by previous authors. The bulk of species in which brochosomes have been reported belong to Miridae [9, 10]. Most members of that family are at least facultatively zoophagous, and some are known to prey on cicadellids [20]. Even the species closely associated with par- ticular host plants and appearing mostly herbivorous may be facultative predators. During this study S. rotermundi, closely associated with the white poplar, displayed cannibalism and sucked out small leafhopper nymphs placed into the rearing tubes. Mirids typically grasp their prey with the legs, which is consistent with the fact that in most specimens examined by previous authors [9, 10] brochosomes were found on the legs (which is also compatible with an aspirator or kill- ing jar-mediated contamination scenario). Potential use of brochosomes as tracers of predaceous or parasitic interac- tions within natural arthropod communities is worth fur- ther study. However, such studies require exclusion of other contamination routes, while the results presented here indi- cate that that may be very difficult. References [1] G. S. Tulloch, J. E. Shapiro, and G. W. Cochran, “The occurrence of ultramicroscopic bodies with leafhoppers and mosquitoes,” Bulletin of the Brooklyn Entomological Society , vol. 47, pp. 41-42, 1952. [2] G. S. Tulloch and J. E. Shapiro, “Brochosomes,” Bulletin of the Brooklyn Entomological Society , vol. 48, pp. 57-63, 1953. [3] G. S. Tulloch and J. E. Shapiro, “Brochosomes and leafhop- pers,” Science , vol. 120, no. 3110, p. 232, 1954. [4] M. F. Day and M. Briggs, “The origin and structure of brochosomes,” Journal of Ultrasructure Research , vol. 2, no. 2, pp. 239-244, 1958. [5] R. A. Rakitov, “Brochosomal coatings of the integument of leafhoppers (Hemiptera, Cicadellidae),” in Functional Surfaces in Biology , S. N. Gorb, Ed., vol. 1, pp. 113-137, Springer, Berlin, Germany, 2009. [6] R. A. Rakitov, “On differentiation of cicadellid leg chaetotaxy (Homoptera: Auchenorrhyncha: Membracoidea),” Russian Entomological Journal , vol. 6, pp. 7-27, 1998. [7] C. H. Dietrich, R. A. Rakitov, J. L. Holmes, and W. C. Black, “Phylogeny of the major lineages of Membracoidea (Insecta: Hemiptera: Cicadomorpha) based on 28S rDNA sequences,” Molecular Phylogenetics and Evolution , vol. 18, no. 2, pp. 293- 305, 2001. [8] A. S. Frost, J. S. Gardner, and M. Nielson, “Scanning electron microscope study of brochosomes of Cercopidae,” in Proceedings of the 52nd Annual Meeting of the Microscopy Society of America, pp. 358-359, August 1994. [9] D. Wyniger, D. Burckhardt, R. Miihlethaler, and D. Mathys, “Documentation of brochosomes within Hemiptera, with emphasis on Heteroptera (Insecta),” Zoologischer Anzeiger, vol. 247, no. 4, pp. 329-341, 2008. [10] D. Forero, “Revision of the genus Carvalhomiris (Hemiptera: Miridae: Orthotylinae),” Entomologica Americana , vol. 115, no. 2, pp. 115-142, 2009. [11] R. A. Rakitov, “Post- moulting behaviour associated with Malpighian tubule secretions in leafhoppers and treehoppers (Auchenorrhyncha: Membracoidea),” European Journal of Entomology, vol. 93, no. 2, pp. 167-184, 1996. [12] J. M. Cicero, J. K. Brown, P. D. Roberts, and P. A. 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Hindawi Publishing Corporation Psyche Volume 2011, Article ID 710929, 5 pages doi:10.1 155/201 1/710929 Research Article Essential Oils of Aromatic and Medicinal Plants as Botanical Biocide for Management of Coconut Eriophyid Mite ( Aceria guerreronis Keifer) Susmita Patnaik, 1 Kadambini Rout, 1 Sasmita Pal, 1 Prasanna Kumar Panda, 1 Partha Sarathi Mukherjee, 2 and Satyabrata Sahoo 1 ' Natural Products Department, Institute of Minerals and Materials Technology (IMMT), Bhubaneswar 751013, India 2 Advanced Materials Technology, Institute of Minerals and Materials Technology (IMMT), Bhubaneswar 751013, India Correspondence should be addressed to Susmita Patnaik, susmitapatnaik007@gmail.com Received 1 September 2010; Revised 30 December 2010; Accepted 11 April 2011 Academic Editor: G. B. Dunphy Copyright © 2011 Susmita Patnaik et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. The present study investigated the efficiency of essential oils extracted from different aromatic and medicinal plant sources on Aceria guerreronis Keifer, one of the serious pests of coconut. The essential oils and the herbal extracts were prepared in two different formulations and were used both in laboratory and field conditions to assess the efficiency of the formulations against the coconut mite infestation. The field trial results showed that reduction in infestation intensity was found to vary between 73.44% and 44.50% at six different locations of trial farms with an average of 64.18% after four spells of treatment. The average number of live mites was higher in the third month old nuts both in the control as well as the treated nut samples. The laboratory experiments on the efficacy of botanical biocide showed that the time taken for dehydration and shriveling of body cells took only sixty seconds. The multilocational field trials revealed the overall efficiency of the biocide to significantly control the eriophyid mite in coconut crop in an ecofriendly and sustainable manner without adopting any chemical pesticide. 1. Introduction The eriophyid mite ( Aceria guerreronis Keifer) is a micro- scopic organism that remains under the perianth of the coconut and has been one of the serious pest of coconut for the last three decades in major coconut growing countries [1-4]. These tiny mites aggregate in colonies in the inner and outer bracts and under the tepals and feed on the meristematic tissues on the nut surface. Due to mite congregation and feeding the meristematic tissue beneath the perianth becomes chlorotic and then cracks. A. guererronis infestation leads to surface scars, reduced fruit growth, and premature fruit fall [5]. The reported yield loss caused by A. guererronis was found to be 34% in India [6]. In the past few years, several studies have focused on the potential use of essential oil formulations in biological control of various insect pest and diseases. The essential oils which get more rapidly degraded into the environment than chemical compounds have been studied for their action against various insect pest of stored products [7, 8]. Recent studies have demonstrated the antilarval and antifeeding [9-11], delayed adult emergence and egg mortality [12], arrestant and repellant actions [13] of essential oils. The present study has been aimed to use these natural derivatives as an alternative ecofriendly means to control the eriophyid mites (A. guererronis Keifer), one of the serious pest of coconut. 2. Materials and Methods The oils herein were chosen based on initial field studies, allowing suitable quantities of acaricides to be used more effectively over a given time interval to meet the multiple demands of efficacy, suitability to mode of application, and minimization of environmental damage. The essential 2 Psyche oils and extracts from Banatulsi ( Hyptis suaveolens ), Tulsi (■ Ocimum santum ), Patcholi ( Pogostemon cablin), Citronella ( Cymbopogon winterianus), Kalmegh ( Andrographis pan- iculata ), Citrus ( Citrus limon ), and Soapnut ( Sapindus emarginatus ) were used after analysis of their active princi- ples against insect pest and diseases. Field trials were conducted at five farms of coconut grow- ing states of India (Karnataka, Kerala, West Bengal, Orissa and Andhra Pradesh (Demonstration cum-seed Production Farm (DSP) and Phillips Farm)) in replicated randomized block design. The botanical formulation in spray and herbal organic manure were applied to infested coconut plants at quarterly intervals by preparing rings to study its effectiveness against the mite. The botanical acaricide was applied on newly pollinated flowering bunches in two ways: one method consisted of spraying at the rate of 25 mL per flower using oil combination diluted in 250 mL water. Protocol two included application of 3 kg herbal organic manure per plant. The formulation was prepared by mixing coir pith and cow dung in a ratio of 1 : 2 along with 1% (w/v) each of Andrographis paniculata and Hyptis suaveolens kept in a pit for three months for composting. The efficacy of the botanical biocide was based on the infestation intensity of A. guererronis from different farms. To analyze competence of the botanical biocide, labora- tory experiments were also conducted. The number of live mites present in nuts of different ages was studied both for control and treated plants. Nut samples from five randomly selected bunches per replication from one to six month old were collected from each of the trial farms three months after biocide application. The nuts were then subjected to counting of mites by a method according to Lawson-Balagbo et al. [14]. The mite population inside the bracts and on the nut surface below the perianth were extracted using 50 ml of IN cetrimide solution, and the mite suspension after collection in a beaker (100 mL) was agitated by blowing air into it for about 15-20 seconds using a pipette for uniform mixing. Immediately, 10 mL of the subsample of the suspension was transferred to De Grisse counting dish, and mites were counted (A). A second sample counting determined left out mites on bracts and nut surfaces (B). A third count was done by direct observation of the bracts and the surface below perianth using stereoscopic microscope to count any left out mites (C). Thus, the total number of mite (N) present per nut was calculated by the formulae: N = 5 (A + B) + C. The samples from nuts of different ages were subjected to statistical analysis. The inflorescence was also examined for presence of eriophyid mite. Essential oils of Hyptis suaveolens, Ocimum santum, Cym- bopogon winterianus, Pogostemon cablin and Citrus limon, and botanical biocide formulation were placed in direct contact with eriophyid mite (A. guererronis ). Ten live mites from each infested nuts from different farms were transferred to a cavity slide under microscope, and 20 pL of the oils or formulation were applied to the slide. Time taken for dehydration and shriveling of body cells was recorded and analyzed statistically through T-test (Data not shown). Treated nut samples Untreated nut samples Figure 1: Effect of botanical biocide on average number of mites with respect to age of nuts. 3. Results and Discussion The botanical biocide treatments against the infestation intensity of the eriophyid mite produced interesting effects (Table 1), lowering the average infestation intensity to 69.37% after six treatments. The pretreatment eriophyid intensity averaged 80.8% (range 58.2-100%) at six trial farms. After first treatment count the botanical biocide exhibited significant effect in reducing infestation by 23.25%. The percentage reduction was essentially similar at the test sites [Orissa (35.16%), Kerala (29.96%), Phillips farm (23.28%), DSP farm (22.12%), West Bengal (15.16%), and Karnataka (13.83%) after first treatment. After second treatment, intensity of mite in the nuts was observed to be reduced at all sites by 33.24%. However, in trial farms of Karnataka and Kerala, mite infestations were higher compared to levels after previous treatments. This may be attributed to the secondary infestation of pathogens. The third treatment also increased reduction by 59.33% with a similar trend followed in the fourth treatment. Results were not significantly different at subsequent treatments. The reduction of infestation intensity in Orissa and DSP farm is significantly higher than the other trial farms (Orissa (73.44%), DSP (71.5%), Phillips farm (67.51%), West Bengal (63.94%, and Karnataka (44.5%)). The statistical analysis of fifth and sixth round of botanical biocide applications showed results at par with the fourth application, thus inferring that the application dosage of the biocide for mite control in coconut can be standardized as four applications per year for most farming locations. The laboratory experiment for number of live mites present in nuts of different age revealed that inflorescences of coconut carried no mite. This supported the result of Moore and Alexander [15] which reports that mites do not infest the meristematic zones of unfertilized coconut flowers. The presence of mites on the nuts collected from one to six- month- old bunches after fertilization supported the findings Psyche 3 e 8 Si s bo •S u o >- A-> *s c CD c .O *4-> cb +-» <73 , cb 3 s 5h <-W o cb o € w w hJ P9 4 Cb c/3 c/3 *c o cb 3 5h cb 4-> (73 , CD o c cb CD S g cu o W>*J 3 2 5 to _ < c ^ g o • 4-> CD P 3 cb bA C CD CQ +-> C/3 CD Cb 44 cb +-» cb C 5-i cb Gd (/J Oh Gd Oh Gd (/5 • j— j NO ON oo CO LO LO of LO LO O CN T— 1 TO tj co cX N> ^ i— H LO CO VO ON Of i— H CN ON o CO i— H of cd P OO NO On NO NO i— H oo NO LO CO CO Of NO LO LO NO LO NO LO H— 4 T\ g y HH ^ W w w o „ K ^ N ^ — s ^ — s ^ ^ 4—i OO ON CO r - H i— H IN Of LO LO LO o IN Ov co LO P cb 4— » ON t-H oo p OO O p LO o CO 3 °° cO c n On On of CO LO ft On OO NO i— H o CO i— H N 5 • oi . (/3 , rJj , Cb 4-> C/3 • CD LO oq ON o ON O r-H o IN oq IN LO bJD O 4 b 00 CO oo CO 00 OI (N CO oi LO 4 -» cb Ph * 4 — > cb 4 — » Ng o OJ of IN LO i— H t— H i— H o ON LO cq o o NO LO O IN of IN CO p ON P of NO 00 01 IN Of ON IN oo ON o LO o ft o NO cd i— H LO cd ON NO oi Of . QJ V 4 H P HH LO X LO X IN LO CN CN i— H CN i— H i— H OI oo oo of o of o LO r - H ON o LO fv LO o H CN H CO H Of H LO H NO H W &H +l X w R CO U X 4 =) a .o +-» co c D 5—i C 4 D 4 b bJD aj a D bJD o 3 +-> c D O 5-1 100 m from the nest [2], our test would not have detected its presence. Because we tested only for responses to signal-based, active scent marks, we cannot entirely rule out the possibility of passive footprint cues, such as those utilized by stingless bees and bumble bees, that might accumulate after many repeated visits [5, 23-26]. The number of visits required to make a feeder more attractive varies among species. A foraging honey bee need land only briefly on a feeder to leave an attractive scent mark [30]. However, in some stingless bees, 20-40 visits are required to make a visited feeder more attractive than an unvisited one [23, 43]. Vespula germanica foragers did not choose a feeder visited 50 or 100 times any more often than an unvisited one [34]. On the other hand, these wasps were shown to follow a trail in the nest entrance tunnel after it had been walked over by more than 200 individuals [48]. However, if such a large number of visits is required to mark a food site with a footprint cue, it would be of little value to foragers. Because we used a carbohydrate food source, our ex- periment cannot rule out the possibility that scent marks are deposited on protein resources. Several swarm-founding wasps scavenge on carrion [49-51], especially those in the genera Agelaia and Angiopolybia. On the other hand, the scent of rotting meat may render active marking of a resource superfluous [8]. Indeed, recruitment was not found in Agelaia multipicta or A. hamiltoni, two species known to exhibit necrophagy [7]. In the tropics, these wasps must also contend with stingless bees and ants that feed on carrion [3, 4, 52]. Wasps may not be able to compete with these insects, especially those that can amass large numbers of foragers at these highly profitable sources using recruitment. Foragers also did not choose the test feeder any less often than the control, suggesting that P. occidentalis does not leave behind repellent scent marks, either. There remains the possibility, however, that repellent scent marks may be left behind if a feeder is depleted. When repellent behavior has been found in bees, the experiments utilized real flowers or Psyche 5 artificial flowers that were depleted after feeding. In contrast, our feeders remained filled. Although we found no evidence for the role of scent marks in forager resource choice, we did find an effect of feeder position for some individuals. Presumably, these wasps learned the relative position of the feeder on the tripod stand using local landmarks and subsequently returned to that same feeder more often. Because scent was weak, visual cues may have been the only reliable cues available. Indeed, visual cues are known to be used by wasps upon return if a food source has not been depleted [53-55]. However, not all individuals displayed a side preference. It is possible that these individuals encountered other foragers at the feeders during a trip, and this interaction caused them to choose a different feeder on subsequent trips. Alternatively, the strength of positional fidelity may have varied among individuals. A study addressing the phenomenon directly is needed to resolve the issue. The apparent absence of scent marking in wasps and its presence in some bees may be related to differences in food sources utilized. Bees derive much of their carbohydrate sustenance from flowers, while wasps get theirs from a variety of sources including fruit, extrafloral nectaries, honeydew, and human refuse [39]. Repellent scent marks left by bees on depleted flowers allow subsequent visitors to discriminate between visited and unvisited flowers (i.e., each flower represents a point source). In contrast, a repellent marking on a non-point source, such as honeydew, would not be as beneficial for a foraging wasp. Yet, like most bees, wasps feed on flowers ([39, 40], B. Taylor, pers. obs.). However, because wasps are restricted by their short glossas to flowers with short corollas or cup -like morphologies, flowers likely make up a smaller portion of their diet compared to bees, and therefore, selective pressure favoring scent marking of these sources may be weak. The application of attractive scent marks to clustered food sources, such as concentrations of honeydew-producing Hemiptera or human refuse, could be beneficial for wasps. However, fruit and human refuse may be similar to rotting carrion in that they could be easily detected by means of their scents alone. Also, the overall distribution of these resources in the environment near P. occidentalis nests, though unknown in this study, may select for an opportunistic foraging strategy. Johnson [56] rea- soned that environments with an abundance of small resources and few large, transient resources would select for opportunism, rather than recruitment and defense of resources. An opportunistic strategy may also allow foragers to find resources more quickly [56]. The seemingly anomalous presence of scent marking in Vespa mandarinia may be explained by this wasp’s unique food [8, 36] . These hornets attack and overwhelm colonies of other social wasps and of honey bees. It is highly unlikely that a single hornet would succeed at this, but by coordinating and attacking en masse they can overcome the strong defenses of colonies that can contain up to tens of thousands of individuals. This coordination is facilitated by the scent marking [35]. For wasps such as P. occidentalis that do not utilize such well-defended food sources, scent marking may not be adaptive. Despite having the machinery for scent-marking swarm emigration routes, P. occidentalis does not utilize it in the context of carbohydrate foraging. This suggests that the benefit-to-cost ratio of the behavior must fall heavily on the cost side. Unlike nest-based recruitment mechanisms that remain cryptic to non-nestmates, field-based mecha- nisms are subject to eavesdropping by non-nestmates and heterospecifics. Indeed, some foraging stingless bees, honey bees, and bumble bees use marks by individuals from other nests and even other species [28, 57]. 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Box 61470, Boulder City, NV 89006, USA Correspondence should be addressed to William D. Wiesenborn, wwiesenborn@usbr.gov Received 13 January 2011; Revised 30 March 2011; Accepted 30 March 2011 Academic Editor; Ai-Ping Liang Copyright © 2011 William D. Wiesenborn. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. I photographed ultraviolet-excited fluorescence of external resilin on insects in 7 orders, 17 families, and 18 genera collected from shrubs and trees alongside the Colorado River in western Arizona, USA. The localized blue-fluorescence characteristic of resilin was emitted by a variety of structures including sutures and wing articulations on Odonata and Diptera and membranous wings, compound eyes, or ocelli on Hemiptera, Neuroptera, and Hymenoptera. Different widespread, but blotchy, light-blue fluorescence was observed on cuticles of immature Orthoptera and adult Hemiptera. Insects in Hymenoptera and Coleoptera fluoresced least. Ranked amounts of fluorescence, relative to body area, were positively correlated with ranked nitrogen contents (%N of body dry-mass) of insects in genera excluding Hymenoptera. Nitrogen concentrations in insect exoskeletons appear to increase as abundances of resilin and other fluorescent, elastic proteins increase. These structural compounds may be an important nitrogen source for insectivorous vertebrates. 1. Introduction Resilin is a structural protein in insects that fluoresces in ultraviolet (UV) light. It provides elasticity to the exoskeleton and was first described, as rubber-like, in the wing hinges and tendons of dragonflies and locusts [1]. The blue fluorescence (maximum at 420 nm) of resilin [2] is emitted by dityrosine and trityrosine, two phenolic amino-acids within the protein’s chains that cross-link the chains together [3, 4]. Greatest fluorescence is produced when resilin is placed in alkaline solution [2] and excited with long-wave UV light (310-340 nm) [3]. The characteristic fluorescence of resilin has been used to detect the protein in a variety of structures on a diversity of insects. Resilin has been found in wing hinges [2] and legs [5] on cockroaches, abdominal springs [2] and wings [6] on beetles, jumping-mechanisms on froghoppers [7] and cicadas [8], wing- vein joints on damselflies [9], tendons [2] and tarsal joints [10] on blow flies, stretchable abdomens on honey ants [11], and venom injectors on honey bees [12]. Resilin may not be the only compound in insects that fluoresces under UV light. Blue flu- orescence by the epicuticle of locusts has been noted [ 13, 14] , possibly resulting from aromatic compounds [13] such as tyrosine -derived cross-links between epicuticular layers [ 15] . Resilin may be associated with insect nitrogen (N) con- tent. The protein contains a high N concentration, estimated at 19% [16], and can occur in near-pure concentrations or combined with other cuticular proteins and chitin [17]. Chitin is a nitrogenous polysaccharide that contains less N (6.9%) than protein and typically comprises 25-40% of cuticle dry mass [17]. Resilin is not sclerotized and therefore easily hydrolyzed [17] and digested by animals. Insectivorous vertebrates, such as birds, may utilize resilin as an N source. N mass in a variety of spiders and insects collected in riparian habitat was related allometrically to body dry- mass, suggesting that most N resides within the exoskeleton, and dependent on arthropod order but not family [16]. Spiders are not known to contain resilin, and abundances of resilin in insects may vary among orders [2]. My objective here is to examine external UV- excited fluorescence on riparian 2 Psyche insects in different families and orders and test if amounts of fluorescence are associated with body %N contents. 2. Methods 2.1. Collecting Insects. I collected insects during the period from 3 May to 15 September 2010 on the Colorado River floodplain within Havasu National Wildlife Refuge in Mohave County, Arizona, USA. Insects were collected within or near a 43-ha plot of trees and shrubs (34° 46' N, 114° 31' W; elevation 143 m), planted primarily for insectivorous birds, 12 km southeast and across the river from Needles, California. Two impoundments, Topock Marsh (1600 ha) and Beal Lake (90 ha), straddle the plot. Insects were col- lected in separate sweepings of Pop ulus fremontii S. Watson, Salix gooddingii C. Ball, and Salix exigua Nutt. (Salicaceae), Pluchea sericea (Nutt.) Cov. (Asteraceae), and natural- ized Tamarix ramosissima Ledeb. (Tamaricaceae) and com- bined sweepings of Prosopis glandulosa Torrey and Prosopis pubescens Benth. (Fabaceae). I also captured flying insects with a Malaise trap. Insects were stored in 70% ethanol. 2.2. Photographing Fluorescence. I examined UV-excited flu- orescence on insects with digital photography. The alkalinity of insects was increased to pH 9 by adding 0.25 N NaOH to the 70% ethanol (4 drops/5 mL). After being treated overnight, insects were removed from the ethanol and dried with absorbent paper. I illuminated each insect with a long- wave UV light-source constructed by replacing the filter on a UV lamp (Mineralight UVS-12, UVP, Upland, Calif., USA) with a filter that only transmits 310-390 nm (Hoya U-360, Edmund Optics no. NT46-442, Barrington, NJ, USA). UV light was projected at a 45° angle downwards 5 cm onto the insect and reflected onto the insect’s opposite-side with a UV- reflective mirror (Edmund Optics no. A45-337). Insects were photographed with a digital camera (Sony DSC-H1), set for around 8 sec exposures, against a black background while illuminated with UV and fluorescent room-lighting. I bal- anced the blue fluorescence with reflectance of visible light by blocking the room lighting with layers of fine-mesh polyester netting. I photographed the insect’s entire lateral view, or its entire dorsal and ventral views if dorsoventrally flattened. Magnification was increased by attaching a reversed 50 mm lens for a 35 mm film camera in front of the digital-camera lens. All insects photographed {n - 47, 1-8 specimens per genus) were collected during 2010 except for an adult Tettigoniidae collected at the same locality during 2009 [16] and kept in 70% ethanol. Color intensity of photographs in Figures 1-5 was increased with Photo-Paint (Corel, Ottawa, Ontario, Canada). 2.3. Identifying Insects. Adult insects were identified at least to genus after being photographed. They were keyed or compared with identified specimens swept from the same plants in 2009 [16]. I assumed nymphal Acrididae to be the same species as an adult Melanoplus herbaceus Bruner swept from the same arrowweed (P. sericea ) plants, the grasshopper’s primary host [18]. Voucher insects were Figure 1: Blue fluorescence in UV light on a nymph (top) and adult male (bottom) Melanoplus herbaceus (Orthoptera: Acrididae). Photos not to scale. Color intensity digitally increased. Figure 2: Blue fluorescence in UV light on dorsum (top) and ven- trum (bottom) of Brochymena sulcata (Hemiptera: Pentatomidae). Color intensity digitally increased. deposited at the Entomology Department insect collection, University of Arizona, Tucson. 2.4. Comparing Fluorescence with Nitrogen Content. I com- pared amounts of fluorescence with estimates of %N in insects collected during 2009 [16, Table 1]. In this previous study, N mass in spiders, adult insects, and immature Acrididae (swept from P. sericea and similar to those in 2010) was measured with Kjeldahl digestion, and %N was calculated from body dry- mass. Mean estimates of %N in Psyche 3 Figure 3: Blue fluorescence in UV light on ventrolateral (top) and dorsal (bottom, anterior at left) views of the thorax of the dragonfly Pachydiplax longipennis (Odonata: Libellulidae). Color intensity digitally increased. insects within the same genera photographed were ranked across genera. Amounts of fluorescence on insects also were ranked across genera. One lateral-view photograph, or a pair of dorsal- and ventral-view photographs, of each genus was printed that showed fluorescence representative of the other specimens within the genus. I arranged prints of genera in ascending order by total area of fluorescence relative to the insect surface-area photographed. Less importance was given to fluorescence on membranous wings, as on Cixiidae and Chrysopidae, due to their thinness and small proportion of body dry-mass. Association between ranked %N and ranked relative-area of fluorescence of insects classified by genus was tested with Spearmans rank correlation [19]. 3. Results Blue fluorescence in UV light was greatest on immature Acrididae (Orthoptera). Nymphs of M. herbaceus displayed a grainy, light-blue fluorescence abundantly distributed over their entire pronotum, lateral thorax, and abdomen (Figure 1). Blotches of fluorescence also were detected on their gena, femur, tibia, and tarsus. Less fluorescence was observed on an adult male M. herbaceus (Figure 1). Deep- blue fluorescence was apparent on its metasternum, metepis- ternum, and part of its mesepisternum, while the bases of its proximal abdominal- sterna also fluoresced. The other orthopteran examined, an adult female tettigoniid ( Scudde - riafurcata Brunner), displayed blotchy blue-fluorescence on its gena and abdomen. Hemiptera displayed varying amounts of blue fluo- rescence. Fluorescence was abundant on the pentatomid Brochymena sulcata Van Duzee (Figure 2). All of its abdomi- Figure 4: Blue fluorescence in UV light on Acinia picturata (Diptera: Tephritidae) (top) and Minettia flaveola (Diptera: Laux- aniidae) (bottom). Color intensity digitally increased. Figure 5: Blue fluorescence in UV light on Chrysoperla sp. (Neu- roptera: Chrysopidae) (top), Hippodamia convergens (Coleoptera: Coccinellidae) (middle), and Dieunomia nevadensis (Hymenoptera: Halictidae) (bottom). Color intensity digitally increased. nal sterna produced a mottled, light-blue fluorescence, and the membrane of each front wing similarly fluoresced in irregularly shaped patches that were not distinctive in visible light. Less fluorescence was detected on the specimen of Reduviidae ( Zelus sp.). Its ventral thorax and abdomen fluo- resced unevenly, whereas on its dorsum the ocelli fluoresced 4 Psyche strongly and the compound eyes fluoresced weakly. The compound eyes of the Cixiidae ( Oecleus sp.) also fluoresced blue, along with the lower margin of the clypeus. Uneven fluorescence was observed on the medial one -third of its forewings. Various structures on Odonata fluoresced blue. Most flu- orescence on the dragonfly Pachydiplax longipennis Burmeis- ter (Libellulidae) (Figure 3) was produced by translucent- white cuticle attached to the axillary and humeral plates [20] below the base of each front and hind wing. The articulations above the wings similarly fluoresced blue. Broad bands of whitish cuticle ventrally joining the thorax and abdomen also fluoresced. Narrow bands of fluorescence were detected between the front coxa and trochanter, at the bases of the middle and hind coxae, and at the margins of the abdominal sterna. Diptera exhibited intermediate amounts of blue fluo- rescence. Fluorescence was most evident on the tephritid Acinia picturata (Snow) (Figure 4). Its haltere was the most distinctive structure that fluoresced, and fluorescence was also observed at the articulation below the wing, along the notopleural and pleural sutures [21], and on sterna at the base of the abdomen. Fluorescence on Tachinidae ( Zaira sp.) was similarly detected at the articulation below the wing and along the notopleural and pleural sutures but also at the base of the front coxa. The lauxaniid Minettia flaveola Coquillett (Figure 4) fluoresced blue at its wing articulation, along the notopleural suture, and at the sutures at the base of the front and middle coxae. The Tabanidae ( Tabanus sp.) showed weak fluorescence at the base of its wings in dorsal view and on the prosternal, precoxal bridge [21] in ventral view. Green lacewings ( Chrysoperla sp. [Neuroptera: Chrysop- idae]) fluoresced across approximately 25% of their wings (Figure 5). Fluorescence differed between the two genera of Coleoptera examined, both in Coccinellidae. Hippodamia convergens Guerin -Meneville fluoresced strongly on the mesepimeron and metepimeron (Figure 5), both light- brown in visible light and in contrast with the dark-brown ventrum. Weak fluorescence was seen dorsally and ventrally on its compound eyes and on the lateral margins of its pronotum. Fluorescence was absent on the lower and upper surfaces, including the hind wings, of Chilocorus cacti L. Fluorescence was absent or nearly absent on Hymeno- ptera. The compound eyes and ocelli fluoresced blue on bees in Halictidae ( Dieunomia nevadensis [Cresson]) (Figure 5), and a bee in Andrenidae ( Perdita sp.) fluoresced along a short, faint line behind the pronotum and below the pronotal lobe. Fluorescence was not detected on the Formicidae (. Formica sp.), Tiphiidae (Myzinum frontalis [Cresson]), or Vespidae ( Polistes sp.) photographed. Insect genera tended to cluster by order when ranked %N was plotted against ranked relative-area of fluorescence (Figure 6). For example, genera in Hymenoptera exhibited high N-content but near-zero fluorescence, whereas genera in Hemiptera exhibited intermediate N-content and abun- dant fluorescence. Ranked correlation between %N and relative area of fluorescence of insects classified by genus depended on order. Nitrogen content and fluorescence were not correlated (r = .02; n = 18; t = .06; P - .95) when 20 15 § 10