L//VX %\9,H HARVARD UNIVERSITY LIBRARY OF THE Museum of Comparative Zoology S4BLIS»tO w. 1 SB § 1 I g THE UNIVERSITY OF KANSAS SCIENCE BULLETIN MUS. COMP. ZOOL. LIBRARY SEP 16 1972 HARVARD UNIVERSITY] BIOLOGY AND IMMATURE STAGES OF PSEUDOMETHOCA F. FRIGIDA, WITH NOTES ON OTHER SPECIES (HYMENOPTERA: MUTILLIDAE) I 1 s 3 By D. J. BROTHERS 8 S § I SB s I | ft S Vol. 50, No. 1, pp. 1-38 August 28, 1972 ANNOUNCEMENT The University of Kansas Science Bulletin (continuation of the Kansas Uni- versity Quarterly) is an outlet for scholarly scientific investigations carried out at the University of Kansas or by University faculty and students. Since its inception, volumes of the Bulletin have been variously issued as single bound volumes, as two or three multi-paper parts or as series of individual papers. In each case, issuance is at irregular intervals, with each volume approximately 1000 pages in length. The supply of all volumes of the Kansas University Quarterly is now ex- hausted. 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Editor Charles R. Wyttcnbach Editorial Board Kenneth B. Armitage Richard F. Johnston Paul A. Kitos Charles D. Michener Delbert M. Shankel George W. Byers, Chairman THE UNIVERSITY OF KANSAS SCIENCE BULLETIN Vol. 50, No. 1, pp. 1-38 August 28, 1972 Biology and Immature Stages of Pseudomethoca /. frigida, With Notes on Other Species (Hymenoptera: Mutillidae) D. J. Brothers TABLE OF CONTENTS Abstract 3 Introduction . 3 Acknowledgments 4 Studies on Pseudomethoca frigida frigida (Smith) 4 Materials and Methods 4 Outline of Biology of Host, Lasioglossum ( Dialictus ) zephyrum (Smith) 5 Outline of Life History of Pseudomethoca f. frigida 6 Invasion of Host Burrows 6 Feeding 12 Oviposition 13 Larval Development and Cocoon Spinning 15 Pupal Development 20 Mating 22 Seasonal Cycle 23 Host Spectrum 24 Descriptions of lmmatures 25 Egg 25 Larval Instars 25 Pupae 29 Observations on Dasymutilla bioculata (Cresson) by Cottrell (1936) 31 Literature Cited 36 Biology and Immature Stages of Pseudomethoca f. frigida, with Notes on Other Species (Hymenoptera: Mutillidae)1 D. J. Brothers ABSTRACT The biology of Pseudomethoca f. frigida (Smith) is described in detail, based on observa- tions made in eastern Kansas in the field and the laboratory. Adult females are effectively ex- cluded from the burrows of the host, Lasioglossum zephyrum (Smith) (Halictidae), by the guard bees, but successful entry is usually made when the burrow is unguarded. Once inside a nest, the mutillid is unmolested by the bees and remains for a long time, ovipositing in many cells. Female mutillicls may consume one or more host pupae or prepupae during this time. Prior to oviposition the mutillid locates and removes the plug to a cell. The contents of the cell are then investigated with the antennae and the sting, and, if all the provisions have been consumed, an egg is laid anywhere in the cell. Host pupae are paralyzed, but prepupae are not. The mutillid recloses the cell with a plug of soil. The egg hatches after about 100 hours. The larva has five instars and feeds externally, consuming the entire host. About 110 hours after eclosion cocoon spinning is initiated. Defecation takes place soon after the cocoon is completed. If there is no diapause, the molt to the pupa occurs about 70 hours after defeca- tion. The pupal stage lasts about 280 hours in the male and 320 hours in the female. After the molt to the adult, the mutillid remains in the cocoon for about 30 hours, and then chews through the cocoon and cell plug. Mating may occur immediately after emergence from the host nest. The male grasps the base of the female's abdomen with his mandibles prior to actual genital union which lasts about 15 seconds. Mated females rapidly cease to be attractive to males. In Kansas P. f. frigida is multivoltine, and overwintering occurs as prepupae. The external morphology of the immatures of P. f. frigida is described. The egg is simple. Each larval instar has 13 postcephalic segments and 10 pairs of spiracles, the 2nd pair being much reduced. The form of the antennae, mandibles and spiracles varies with the instar. The pupae are similar to the adults but are spinose, especially on the abdomen. Some sutures are visible on the dorsum of the mesosoma in the female pupa and the sting is exserted and curved dorsally over the metasoma. A summary of unpublished observations by Cottrell on the biology of Dasymutilla bioculata (Cresson) in Minnesota is presented. In this species the female gnaws a hole in the bembecine host cocoon and oviposits in the cocoon only after the host has defecated. The oviposition aper- ture is sealed by a salivary secretion. The egg hatches after about three days. Although Cottrell observed four larval instars, there are probably five. Spinning begins about ten days after hatch- ing. The pupal stage lasts about 10 to 12 days. D. bioculata is usually univoltine but some in- dividuals may diapause (as prepupae) for more than one season. Low temperature is not neces- sary to break diapause in all prepupae. Mating takes place soon after emergence, and the male does not grasp the female with the mandibles. Copulation lasts about 20 seconds. Males do not persist in copulation attempts with previously mated females. INTRODUCTION this family is scanty. Detailed biological Despite the size of the scolioid family information has been published for Smi- Mutillidae (4,000+ described species), cromyrme rufipes (F.) (Crevecoeur, 1930; knowledge of the biology of members of Marechal, 1930), three species of Sphaer- opthalma (Photopsis) (Ferguson, 1962) 'Contribution number 1471 from the Department of „ i . „ 1^„„„ -„„.. C -\a *mn c. , T. , T. . F Tr and to a lesser extent tor M nulla europaea entomology, University of Kansas, Lawrence, Kansas f 66044. L. (HofTer, 1886; Jordan, 1935) and Chres- The University of Kansas Science Bulletin tomiitilla glossinae (Turner) (Lamborn, 1915, 1916; Heaversedge, 1968, 1969a & b, 1970). Additional brief observations on mating, host records and other such bio- logical information are mostly hidden in the literature on other insects with which Mutillidae are associated. Mutillidae are parasitic on the resting stages (usually the prepupa or pupa) of other insects, including aculeate Hymenop- tera, Coleoptera, Diptera (Mickel, 1928) and Lepidoptera (Seyrig, 1936; OlsoufierT, 1938). There is an ambiguous record which apparently indicates parasitism of diapausing adult Pentatomidae (Hemip- tera) (Mellor, 1933), although in this case the mutillid was doubtless hyperparasitic through a tachinid fly, since Morris (1930) reported that the tachinid parasites of this bug were subject to severe para- sitism. Invrea (1950) noted that Smicro- myrme aitsoniu Invrea was hyperparasitic on an isopod crustacean through a sar- cophagid fly. Host records exist for less than five percent of the species of Mutil- lidae, and nothing is known of the hosts of five subfamilies (Eotillinae, Typhocti- nae, Apterogyninae, Pseudophotopsidinae and Rhopalomutillinae). In view of the meager knowledge of the biology of Mutillidae, a detailed study of the life history and biology of Pseudo- methoca f. frigida (Smith) was conducted in connection with rearing experiments on its host, Lasioglossum zephyrum (Smith). A summary of unpublished investigations on Dasymutilla bioculata (Cresson) by Cottrell (1936) is also presented. ACKNOWLEDGMENTS The assistance of Mr. Dwight R. Kamm and Mr. Edward M. Barrows in the field is gratefully acknowledged. This study would not have been possible without the use of facilities primarily involved in studies (sup- ported through National Science Foundation Grant GB 8588 X) by Dr. Charles D. Michener on the origin of sociality in halic- tine bees. This paper is thus a by-product of that grant. Thanks are also due to the fol- lowing persons for their comments on parts of or the entire manuscript: Dr. C. E. Mickel, Tucson, Arizona; Dr. C. D. Miche- ner, Dr. P. D. Ashlock, Mr. W. L. Overal, and Mr. G. Gordh, all of The University of Kansas. Thanks are also due to Mr. R. G. Cottrell, Valley Center, California, and Dr. A. C. Hodson, Head of the Department of Entomology, Fisheries and Wildlife at the University of Minnesota, St. Paul, for per- mission to include a summary of Cottrell's thesis. Portions of this study were under- taken during tenure of a traineeship from the National Science Foundation awarded through the Committee on Systematic and Evolutionary Biology at The University of Kansas. STUDIES ON PSEUDOMETHOCA FRIGIDA FRIGIDA (SMITH) Materials and Methods Field observations on adults of P. f. frigida were made at three nesting sites of L. zephyrum near Lawrence, Kansas; two of these sites were banks along small streams which dried up periodically and the third was along the banks of the Wakarusa River, the principal site at which Batra (1966; fig. 3) studied L. zephyrum. Live adults of P. f. frigida were brought into the laboratory for ob- servations on mating and activity within the host burrows in artificial nests of L. zephyrum. These consisted of a pair of glass plates separated by a layer of soil in which the bees constructed burrows and cells (see Michener a\u\ Brothers, 1971). Nests containing cells with immatures in various stages of development, and from which the adults had been removed, were kept at approximately 22° C. The "win- dows" in the sides of the cells were en- larged by removal of some soil around the cells. A female of /'. /. frigida was intro- Biology and Immature Stages of Pseudomethoca f. frigida duced into the burrow and the nest was sealed to prevent her escape. The nests were kept in the dark as much as possible to simulate natural conditions; it had pre- viously been found that females of Dasy- mutilla bioculata would oviposit in cocoons of the bembecine hosts more readily in the dark (Cottrell, 1936). Each nest was in- spected at intervals of 30 minutes or less. When a mutillid was noticed working in the region of a cell, her activity was exam- ined under a stereo-microscope. Observa- tions and measurements of the immature stages were made every few hours at mag- nifications of 25 X and 50X. Experiments involving the interactions of bees and mutillids were performed by introducing mutillids into active artificial nests. Details of the life history and behavior were obtained from a varied number of observations. Interactions between mutil- lids and bees in the field were observed upward of 20 times, and mutillids were introduced into active artificial nests on 12 occasions. At least 20 introductions were made into four different artificial nests containing immatures only, but observa- tions on host-feeding were made on only one mutillid and reactions to cells with contents unsuitable for oviposition were noted only about five times. The complete oviposition sequence was observed three times, although incomplete observations were made on eight additional ovipositions or other reactions of mutillids to cells with contents suitable for oviposition. General aspects of the development of immatures were noted on 21 individuals and detailed notes were made on seven males and one female and an additional female pupa. Successful mating was observed twice in the laboratory and eight unsuccessful at- tempts were noted. Since larvae vary considerably in size, depending on degree and manner of pres- ervation and on age, the descriptions of the larvae are based on a single individual of each instar described. The proportions derived from the measurements, especially those of the more rigid structures, should, however, be relatively constant for each instar. The terminology used in the larval descriptions is based on that used by Michener (1953) and Evans (1965), with the format approximately following that of Evans for easier comparison with his descriptions of larvae of the related family Tiphiidae. Outline of Biology of Host, Lasioglossum (Dialictus) zephyrum (Smith) The host, L. zephyrum, is a small sweat bee (Halictidae, Halictinae), individuals being 5-7 mm long. Mated, overwintered queens establish new nests in early spring. Each queen usually excavates her own nest, constructing and provisioning a few cells and laying an egg in each one. The queen then becomes inactive until the first brood emerges a few weeks later. Sub- sequent broods ultimately replace the over- wintered queens but colonies continue dur- ing the entire summer, the number of bees in each nest increasing as the season pro- gresses. There is a gradation between mated, queenlike individuals and unmated workers with undeveloped ovaries. When two or more bees occupy a single nest, one usually remains at the entrance and acts as a guard, preventing intruders from entering the nest. Burrows are more or less at right angles to the surface of the stream or river bank and may form rather extensive aggregations. At the end of the summer most of the young females mate and overwinter in the old burrows. As in all halictines, the larvae do not spin cocoons, the pupae lying naked in the cells. For further details of the biology of L. zephyrum see Batra (1966) and Michener et al. (1971). The University oh Kansas Science Bulletin Outline of Life History of Pseudomethoca f. frigida P. j. frigida is a small mutillid (Sphaer- opthalminae), 4-6 mm long, with brown, wingless females (Fig. 1) and black, winged, males (Fig. 2). Adults emerge Erom pupae in late spring and females enter the burrows of the hosts which are various species of halictine bees, commonly L. zephyrum. The mutillid is usually re- pulsed by a guard bee at the entrance to an active burrow, but readily enters an un- guarded burrow. After successful entry, a female mutillid locates closed cells and feeds on one or more prepupae or pupae of the host. The mutillid oviposits in cells containing pupae or larvae which have finished feeding, the egg being laid any- where in the cell which is then resealed. The egg hatches in about 100 hours and the larva feeds externally on the host, often changing its position and making numer- ous feeding punctures. There are five lar- val instars. About 110 hours after eclosion and once the host has been consumed, the cocoon is spun and defecation occurs. Dur- ing spring and summer pupation takes place about 150 hours alter the start oi cocoon spinning; in autumn prepupae dia- pause, pupation occurring the following spring. The pupal stage lasts about 2S0 hours for males and .^20 hours for females. After molting, the adult remains in the cocoon tor about 30 hours before chewing through the anterior cn<.\ of the cocoon and the plug ot the cell. Mating takes place soon after emergence from the burrow. Invasion of Host Burrows Adults oi /'. /. frigida emerge Erom the pupae slightly later than their hosts, start ing in late April or early May. At first the mUtillids are rare, but they are lound in increasing numbers at the- lusting sites of L. zephyrum as the season progresses. Although the Eemales may become quite common during the summer at some sites, the males are encountered much more rarely. The wingless females search the river or stream banks more or less ran- domly for the burrows of the bees, con- tinuously vibrating the antennae and run- ning over the surface of the soil, investi- gating irregularities and especially small holes. Although movement is apparently random, the mutillids tend to work their way up the surface of the bank. When a mutillid reaches the top, it walks along the bank and comes down a short distance. Since the burrows of the bees tend to be concentrated in the top meter of the bank, any tendency for the mutillids to move upwards to this region will increase the likelihood of their encountering the host burrows. When a mutillid approaches within a few centimeters, the guard bee often partly emerges from the burrow. The bee faces the intruder, swivelling around if the mu- tillid walks past (see Batra, 1966; fig. 25). If the mutillid approaches closer, the bee may bob in and out of the burrow en- trance, snapping its mandibles open and shut. Ii the wasp approaches within about one centimeter, the guard usually retreats, turns around just inside the burrow en- trance and blocks the constricted entrance with the apical terga of the metasoma, ef- fectively sealing the burrow. Under such circumstances the mutillid may try to squeeze past the guard and may even at- tempt to dig [last. It is usually unsuccess- t nl, and alter a lew seconds it searches elsewhere. Sealing ol the burrow entrance in this way is common in most species of halic- tines in which more than one bee occurs in a nest, and similar responses to /'. /. fri\>i