Historic, archived document Do not assume content reflects current scientific knowledge, policies, or practices. 12, 1923 By Wiu1am Mippteton, | Scientific Assistant, Forest Insect Investigations. wre CONTENTS. — 2 een Page Page. JUST Te eS aes 28 ee BARE ATASILOS 5 So. can oo wei Steiepe pep ep = Oa 16 VE ae ee eo ee ee fb {RISB ooo 5 a2. eos or ote cae oes See ee 17 Life history and seasonal history............... 7 | Distribution in the United States.............. 20 Effect of meteorological conditions............- 14. |; Keoneniic importanee: 3: -b.5 5 2: .-s hie eee 20 ee WEBPCHESIN =. =. ot. oes See eet ace o so they Centrols So 22 2, oe es er eee 21 INTRODUCTION. A European insect, the imported pine sawfly,? has recently been found defoliating young pine trees in nurseries and on estates in cer- tain of the New England and North Atlantic States. This bulletin contains descriptions of the principal stages of the species and some information on its life history, host plants, distri- bution, and importance, together with a brief discussion of its control. The data presented are based on investigations of the sawfly con- ducted at the eastern field station of the Forest Insect Investigations, Bureau of Entomology, at East Falls Church, Va. The studies began with the receipt of material in August, 1915, and continued until the spring of 1919, when the last adults emerged in the cages. Inasmuch as the species was an introduced and dangerous one which had not become well established in this country, great care was exercised in the cage work, in order to prevent its escape. A special double-walled, screen-wire insectary was constructed to which en- trance was had only through a vestibule, and all the experiments were performed on young trees transplanted into this inclosure. DESCRIPTIONS. The following descriptions have been prepared, so that this species can be recognized in its principal stages. ‘Those of the adult are by S. A. Rohwer. 1 This bulletin was prepared under the direction of S. A. Rohwer, to whom the author is indebted for many et suggestions in conducting the investigations. The descriptions of the adult insects are by Mr. Rohwer. The majority of the material from which these studies were made was obtained from Dr. W. E. Britton, State entomologist of Connecticut. 3. Diprion simile Hartig, order ee suborder Chalastogastra; superfamily Tenthredinoidea; family Tenthredinidae; subfamily Diprioninae. ’ 53373—23—Bull. 1182 —1 ; 7 Tare ne q a 2 BULLETIN 1182, U. S. DEPARTMENT OF AGRICULTURE. ADULT. This species is the only North American representative of the genus Diprion and may be readily distinguished from the other Nearctic species belonging to the subfamily Diprioninae by the large and densely punctured metascutellum. Thespecimens which have been examined show very little variation, and all seem to represent the typical form of the species. Female (Fig. 1, a).—Length 7 to 9 millimeters. Clypeus truncate; head with large, rather close punctures; postocellar area convex and more than twice as wide as long; postocellar furrow well defined; antenna distinctly tapering, the joints much broader than long and with very short rami (apical joints practically without rami), third joint distinctly longer than the fourth; scutum shining, with large, distinct punc- tures; scutellum and met- ascutellum opaque and with the punctures closer; tibial spurs simple; pad- like part of sheath ellip- tical in outline and close to the median line; apicai sternite deeply angulately emarginate medially, lancet with nine rows of regularteeth. Black with yellow markings; head black except yellow clyp- eus, supraclypeal area, and scape; thorax yellow with the following parts black: Sternum, mesepi- meron, large spots on pre- scutum and scutum, lat- eral part of scutellar area, and metascutellum; ab- domen yellow with ter- gites 3 to 6 inclusive and median spots on following two black; legs, except the somewhat dusky fem- ora, yellow; wings hya- line, venation pale brown with stigma somewhat darker and the costa somewhat paler. Male(Fig.1, 6).—Length 5to7 millimeters. Agree- ing with female in general Fic. 1.—Diprion simile: a, Female; 6, male. structure; antenna long, the basal rami slightly less than half as long as half the flagellum; hypandrium dis- tinctly punctured, broadly rounded posteriorly; head and thorax more coarsely punctured than in the female; valves of penis, when seen from the side, broad and the ventral margin armed with small, widely separated teeth. Black; venter of ab- domen and legs beyond trochanters dark rufous; wings hyaline, venation pale brown, costa paler. EGG AND EGG SLIT. The eggs of the imported pine sawfly are about 1.5 millimeters long, with straight sidesand bluntly rounded ends. They are oval in crosssection, being 0.5 millimeter on the greater transverse diameter and 0.25 millimeter on the lesser transverse diameter. When first laid the eggs are pale whitish blue, translucent, shining, much like gelatin, and somewhat smaller than the above dimensions. After several days, development becomes marked by swelling and the color appears bluish green. When about to hatch they are quite swollen, sometimes as long as 1.75 millimeters, and are dark green. (Fig. 2, b.) roe slit is cut into the -eonvex portion of the ee ee two textures (Fig. 2, _¢). The basal portions THE IMPORTED PINE SAWFLY. 8 The eggs are laid in slits in the needles (Fig. 2,a). Adults emerg- ing early lay in last year’s needles, but those emerging when the : eeecnt year’s needles are of sufficient size appear to prefer these. e number of eggs deposited in a single needle varies. In the needles observed, from 2 to 16 eggs were laid, with an average of 8. Where more than one egg is laid the egg pockets adjoin one another, with merely a wall be- tween. The pocket or needle irom an edge at an angle and the tissue composing the walls of the slit is of of these walls are the rather tough outer coating of the needle and the apical por- tions are delicate membranes, appar- ae — “ om needle pulp, which are agro acetone Nh tah ee ressed together fol- %?— Riga sine. o, Bar in portion in pnd os show. owing the laying of the egg, seal it in place, and somewhat conceal it. As the egg increases in size, it parts these lips and becomes exposed. When freshly made the cuts are yellowish green and the needle dark green, but as the eggs mature the cuts become somewhat brownish and the needles yellowish. LARVA. The following description * was made from a full-grown, sixth-instar larva of Diprion simile which had been preserved in alcohol. (Fig. 3.) Length 20 millimeters; maximum breadth, across the metathorax, 4.5 millimeters. The head is circular in outline viewed from in front and the front plane slightly convex viewed from the side; frons and epicranium with a few fine hairs; epistoma with 4 hairs; labrum with 4 hairs; eye disks not elevated, eyes large, lenses convex; antenne between and slightly closer to pleurosto- mata than eyes, composed of cone and two disks or partial ring joints; maxille Fic, 3.—Diprion simile: Full-grown larva. with cardo, stipes, palpifer : and 4-jointed palpi, galea, and lacinia; lacinia not flattened, rather triangular in outline viewed from apex, armed with large hornlike process or seta on the side toward labium and with rather large setze forming an apical transverse row on the side of the lacinia parallel with the interior surface of the trophi; labium with palpiger and 2-jointed palpi. Thorax with the tergum composed of areas A, B, C, and D; A excepting in the prothorax, B, 8 The terminology used in describing the larva is that used by the writer in the descriptions of Neodi- prion lecontei (Fitch) (Jour. Agr. Research, v. 20, no. 10, p. 741-760, 1921), with the changes adopted in ‘Some suggested homologies between larvez and adults in sawflies’”’ (Proc. Ent. Soc. Wash., v. 28, no. 8, p. 173-192, 1921). 4 BULLETIN 1182, U. S. DEPARTMENT OF AGRICULTURE. and C with a few setz or spines; A of the prothorax bare and constricted and D bare; — alar area wanting or incorporated in the spiracular area of the prothorax, large in the mesothorax and metathorax; in the pleurum, preepipleurite large, well defined, and possessing setz or spines; postepipleurite large, well defined, spined in prothorax but bare in mesothorax and metathorax; prehypopleurite large, triangular, of heavy chitin and sparsely, finely haired; posthypopleurite large with a prominent spined lobe; legs with 4 joints and an apical claw, joint 3 with small soft pad on inner side at apex. Abdomen with the tergum of urites 1 to 9 inclusive composed of areas A, B, C', C?, C? and D; A, B, and C? spined, C', C%, and D bare; urite 10 consists tergally of the epiproct, which is rather thickly spined and without pseudocerci; spiracular area present on urites 1 to 8, wanting on urites 9 and 10; alar area present on urites 1 to 9 (reduced on urite 9), absent or indistinct on urite 10; the pleurum with preepipleu- rite and postepipleurite distinct, rather large and spined on urites 1 to 8, reduced, indistinct, but spined on urite 9, wanting or indistinguishable on urite 10; hypopleu- rite distinct but not divided into prehypopleurite and posthypopleurite, unspined and bearing the uropods on urites 2 to 8 inclusive, indistinct or wanting on urites 1, 9, and 10; uropods well developed on urites 2 to 8 inclusive, not developed on urites land 9, and developed as postpedes on urite 10. The head is black and shiny, with the eyes yellowish and the membranes about antenn®, mandibles, trophi, and between labrum and epistoma whitish. The thorax is yellow, much darkened with velvety black which becomes greenish with growth and age; legs black. The abdomen is yel- low, marked as thorax; uropods, postpedes, ventral region, and anus undarkened. Most of the body, the tergum and pleurum of the thorax and abdomen isa mottled black and yellow of rather regular pattern. The depressed portions of the body wall are black and the raised portions are yellow, giving much the appearance ofa yellow larva dipped in some adhesive black coloring matter and then allowed to wear off the mate- rial darkening its more prominent areas. LARVAL INSTARS. In the study of Diprion simile the experiments on the larve offered an excellent opportunity to determine the number of larval instars and the size of the larve during each instar. For conven- ience, this information is arranged in tabular form below. It will be noted that the species has six feeding instars in larve producing female adults and five feeding instars in larve producing males. This feature was remarked upon by the writer in treating Cladius isomerus Norton in a recent paper on the subfamily Cladiinae ‘¢ and is probably common to sawflies, since H. C. Severin ® records a similar difference in the number of instars between larve producing ee and female adults in his account of Neuwrotoma inconspicua orton. The prepupa of Diprion simile is rather well defined and differs Aas the larva sufficiently in general appearance to be readily recog- nized. 4 Rohwer, S. A., and Middleton, William. North American sawflies of the subfamily Cladiinae. With notes on habits and descriptions of larve by William Middleton. Jn Proc. U.S. Nat. Mus., v. 60, art. 1 (no. 2396), 1922. See p. 19. 6 Severin, H.C. The plum webspinning sawfly. State Ent.S. Dak., Tech. Bul.1. 1920. Seep. 11, 26, tables 2, 3. Severin finds six instars for larvee becoming males and seven instars for those becoming females. This larval period, however, covers the entire time spent by the larve above ground and therefore includes the stage recognized in the present paper as the prepupa. THE IMPORTED PINE SAWFLY. 5 ~Tasie. 1.—Average size of larval instars and prepupa of Diprion simile, in millimeters. . Head. Body length. Nowiber e eb AM hd AER LE OF ee res Instar or stage. used to : | Height. | Width. | Young. oa Ek - $ | Mili- | Miui- | Mili- | Mili- | Mili- meters. | meters. meters. meters. meters. ee ee ek eS | 0.75 | 0.50 2.75 6.0 11 EE a ee ee eee 95 | 15 4.00 | 8.0 11 ras Senses rete fe Oe, coe fatdwnad Shs 1:20") 1.00 7.00 12.0 8 | SEE ic en eee | 1.60 | 1.40 8.00 | 15.0 7 REO SENS: LL Sah 0 2) ea ee = 2.00 | 1.80 14.00 | 20.0 5 ere Propunay.--.---2-----------=---2--------- 2.00 1.80 214.00 | 313.0 2 V (female antepenultimate)...............-...-...- 1.95 | 1.65 11.00 | 18.0 3 eR IP RMCIMUA NALS) 2. sere n' cne a aoe = 35/0502 2.20 | 2.00 15.00 20.5 3 Sebeetale prepiupa).. o.. 0... 4.5... 3. --ee-ns2e-s-s 2. 20 2.00 219.00 312.0 2 1 These larve were reared in isolation and measurements were made at frequent intervals. The dimen- | sions obtained from them are perhaps few in number but accurate and from an instar or stage positively | known. The averages obtained from these larve were found to apply to larve in the general rearing cages. | 2 Largest. Prepupz do not feed and grow. They contract with development and the spinning of the ocoon. F 3 Smallest. The different instars of the larve of Diprion simile are colored as follows: Instar I.—Before feeding: Head whitish, eye spots blackish. Body dull gray. After feeding: Head and legs become blackish. Instar I] —Much the same as the first instar. . The dorsum darkens somewhat at the approach of the time to shed. Instar III.—Head black. Body green to bluish gray. The day before molting to the fourth instar the larva begins to show dark dorsal, supraalar, and epipleural lines. This change previous to shedding is doubtless caused by the darker coloration of the approaching instar showing through the skin about to be shed. Instar [V.—Head black. Body considerably darkened, greenish black and yellow, pattern of mottling similar to that of full-grown larva. The larva pales somewhat With age or increased size. Instar V.—Head black. Body velvety black and yellow. The black becomes greenish with age or increased size. Instar VI.—Head black. Body velvety black and yellow. Each instar seems to have two poorly marked phases; first, a rapid growing period, usually covering the greater part of the instar, during which the body increases in length; and, second, a preparatory period preceding molting during which there is a retardation in growth or even occasionally a contraction. The accompanying dia- gram (Fig. 4) shows the records of growth of a male and a female larva m body lengths, instars and days, and illustrates this feature. PREPUPA. The prepupa of the imported pine sawfly does not feed and its development is accompanied by contraction rather than increase in size. The cocoon is spun in this stage and, protected within, the prepy a changes gradually as it develops into the pupa. The following description is from a prepupa preserved in alcohol which had not begun the spinning of its cocoon. Prepupe after spinning do not differ structurally from those which have not spun but are considerably more contracted. A prepupa that is to produce a female adult will measure about 19 millimeters in length before spinning its cocoon, while, after spinning, it will be about 12 milli- meters long. 6 BULLETIN 1182, U. S. DEPARTMENT OF AGRICULTURE. The size of the prepupa is discussed under ‘‘Larval instars.” The prepupa of Diprion simile is similar to the larva, in structure, with the armature or spines reduced to indistinectness. The head is grayish white, eye disks and apices of mandibles, only, black. The thorax and abdomen are both pale greenish white, with narrow green, dorsal longitudinal stripes and broader green supraalar to alar longitudinal lines which are broken by yellowish spots on B, C!, C?, the pale spiracular area, and the yellowish alar area. Pleurum pale but for a pair of greenish pleural spots. Venter, uropods, postpedes, anus, and epiproct pale, the latter faintly grayish. COCOON. The cocoons (Fig. 5) of Diprion simile are cylindrical, with hemispherical ends. They are single-walled, of fine texture, rather glossy, fairly stiff, but thin. Cocoons from which males emerge are somewhat smaller than those from which females issue, 7 by 3.5 millimeters being the size of the former, while the latter are 9.3 by 4 mili- meters. The cocoons are usually dark brown; sometimes they are pale tan when made but become dark brown within a week or 10 days, and in one instance a whitish cocoon was spun which failed to become colored. AIA AWE STA YW SINE Q + nN QPNEOHYRTRAS Hong CVV LHRINARS Ss 2 lah TEIMIMSISIE AT yayeye PTTITTIIy LITT I Ph eee is: | SSSSnnSER SERQESA05 UN aagSe0000 RERSEORD ee CAAA cna eenen FE att Ci Saeneuese | 19 sOSGRRI'S | peas 8: S 4 ee Fk paces'ia PN SG008 NOE. C8 Re - Su) ay scesceses RS » 2- oF dteeescesss= ee SST SEEEBEEES Nae 2 AWA Hae G13 = Cold? Sotsssssss20s vai’ inseeeeece eee EHS eaeceeee eee 5 ee HHA seaeceyoneeoe \ er 587.6): 4508e0e8 BOS550 {mabena Sgr SAE HE Nano. j van Beanee BaP as) iP Shee Q “a Oe 42URTReRBeReS SES58 s5Re5088 B) SCSa eee Rees art Tir 7 Pg TT PEE 25 iat ee ittssat dae 2 Hee FEM ay ececense BES SRaEDR } &Y 48ERR BERS (cine | BoP SaaS Ee P 4B SESR05E8 EsSCUBDREBEBA ! ADRES SORES RSE Fic. 4.—Diprion simile: Larval growth charts. Stage of larva indicated by large figures. Female has six stages, male five. Growth records are shown for a single female and a single male larva. In captivity the cocoons were often spun on the needles, and while this may be the rule in nature the writer is inclined to believe that many of the prepupz of this species, like those of Neodiprion leconter, will make their cocoons in the ground for the sake of the prone non thus afforded in winter. This view is supported by a furopean observation ® which records the summer brood cocooning on the branches of the tree while the winter brood makes its cocoons beneath the tree. The cocoon is spun of a “silken” thread from the vicinity of the mouth.’ The end of the cocoon inclosing the caudal extremities of the prepupa is made first, then the anterior end is inclosed by a sidewise motion of the head. After the entire cocoon is formed the prepupa works over the inside, plastering a sticky substance to it. This coating makes the glossy inner surface. 6 Britton, W. E. A destructive pine sawfly introduced from Europe. Jn Jour. Econ. Ent., v. 8, no. 3, D. 379-382. 1915. Seep. 381. T This thread doubtless comes from the apex of the labium, where the writer has observed a similar sub- stance protruding in some prepupe of Cimbez americana Leach in his possession. THE IMPORTED PINE SAWFLY. 7 LIFE HISTORY AND SEASONAL HISTORY. The experiments to obtain data on the life history and seasonal history of Diprion simile were distinct from those pertaining to the choice of host plant and also from those pertaining to the ability of the insect to reproduce parthenogenetically. Pinus sylvestris was chosen as a host for this work because it seemed to\be favored by the sawfly and because it had been shown to be a successful host in this locality by previous tests. In no instance was copulation observed, but opportunity for fertilization was provided by keeping constantly with each female at least two males in excellent condi- tion. These experiments were made with small cylinder cages of screen wire on a steel frame, 14 inches in diameter by 24 inches high, the top of which was removable to permit easy access to the interior for observation or handling the material. These cages were placed over young trees of Pinus sylvestris, and adults of Diprion simile were then libe- rated within. There were also certain spe- cial life-history and seasonal-history stud- les, particularly some in which observations were made on larvee Fic. 5.—Diprion simile: Cocoons. a, Occupied by female, unopened; ot this sawfly reared b, occupied by male, unopened; c, after emergence of female; d, emu deter csutococoon’ chiowing emergence Kole ofa diplerous parasite) mine the number and duration of the 4instars and the infiuence of the sex of the individual upon this phase of development. The data presented in the following account of Daprion simile show some singular likenesses and contrasts with the life of the related Neodiprion lecontei.8 It would be well to emphasize that the imported pine sawfly has the same apparent division of the emergence period into Broods A and b. It differs somewhat from Leconte’s _ sawfly in the course of its issuance, a fact which may be explained _ either as inherent in the species or as caused by change of environ- ment. The climate and other natural factors in the United States may be so different from those to which it is accustomed that it is unstabilized here. Should this prove true, the situation with regard to Diprion simile may become very different within a few years, and the insect may even become a more serious problem than it now promises to be. The imported pine sawfly has important life-history and seasonal-history advantages, and if it can become a recognized depredator while unstabilized by the conditions of this _ new environment, the destructive possibilities of the species when _ itis properly adjusted will be necessarily greater. In that case it may possibly present a new life history and seasonal history. ADULT EMERGENCE. The emergence of adults from the cocoons of a single colony of the larvee of Diprion simile occurs over a considerable period, approxi- mating a year. This emergence is not continuous, but divides itself 8 Middieton, William. Leconte’s sawfiy, an enemy of young pines. Jn Jour. Agr. Research, v. 20, no. 10, p. 741-760. 1921. 8 BULLETIN 1182, U. S. DEPARTMENT OF AGRICULTURE. into a period early in the year and a period late in the year. The adults are separated into Brood A, those issuing in the first emer- gence period following cocooning, and Brood B, those issuing in the second emergence period following cocooning. The early emergence period occurs from April to June and is not distinctly separated from the later emergence period, which occurs during July and August. The rearing cages, however, show a marked decrease in the number of adults coming from cocoons during}June. The following summary of records of the issuance of adults shows the duration of this period and its tendency to divide into two parts, the months of maximum emergence being April, May, and July. Larve and pupz collected in August, 1915: 1 adult emerged in August, 1915. 77 adults emerged in May, 1916. 5 adults emerged in June, 1916. 1 adult emerged in July, 1916. Cocoons collected in April, 1917: 16 adults emerged in April, 1917. 95 adults emerged in May, 1917. 2 adults emerged late in June, 1917. 2 adults emerged in July, 1917. 1 adult emerged in April, 1918. Larve cocooning in June of various years: f 2 adults emerged in June of the same year in which they cocooned. 24 adults emerged in July of the same year in which they cocooned. 1 adult emerged in August of the same year in which it cocooned. 7 adults emerged in April of the year following that in which they cocooned. 8 adults emerged in May of the year following that in which they cocooned. LONGEVITY OF ADULTS. The average length of life for adults of Diprion simile was 6.6 days, with a range from 3 to 11 days. The life of the female was slightly longer than that of the male, the former averaging 7.5 days, with a range from 5.5 to 11 days, while the latter averaged 5.8 days, with a range from 3 to 9 days. The life of female adults known to have laid eggs was somewhat longer than the hfe of those not known to have laid eggs. Females laying eggs averaged 7.75 days, those not known either to have laid eggs or not to hae laid eggs averaged 7.66 days, while those known not to have laid eggs averaged 7 days. The two shortest-lived males were the progeny of parthenogenetic females. Only two of these were available for this study, and these lived, one 3 and the other 4 days. PROPORTION OF SEXES. The males seem somewhat to exceed the females in number, and from a series of 227 adults issuing from cocoons in certain of the cages, 134, or 59 per cent, were males, while 93, or approximately 41 per cent, were females. MATING. Mating was not observed. At different times three males were caged in glass vials with a single unfertilized female without their paying her the slightest attention. This, however, was probably due to the close confinement of the sawflies under observation, which tended to distract them and prevent or discourage natural behavior. The fact that from the life-history and seasonal-history THE IMPORTED PINE SAWELY. en experiments both sexes were obtained in the progeny, while, as will be stated farther on, in parthenogenetic experiments only male adults were obtained, indicates that mating is a regular occurrence. OVIPOSITION. The eggs are laid in the needles of the pine and the adults emerging from their cocoons early in the year oviposit in the old or last year’s needles, while the adults emerging later in the year lay their eggs in the needles of the current year. The following note, made in obser- vations on the habits and activities of the adults in the life-history and seasonal-history cages, shows the increase in attractiveness of the current year’s needles. All the females, except the one emerging at the latest date, i. e., June 23, 1916, laid their eggs in the old or grown needles, but this female, possibly because of the advance of the younger needles, delayed her oviposition several days and then apparently first attempted egg laying in these new leaves. After two slits or thrusts, possibly having succeeded in laying an egg in one of these, she began on the old needles and finished her work on them. This note seems to indicate a preference for the young needles which were still too small for this female to oviposit in them. The following account, taken from cage notes made during these experiments, gives an accurate description of the method of ovipo- sition : : The female begins laying eggs near the base of the needle and works toward the tip, making a new incision for each egg. In oviposition the mandibles usually close upon the needle; the antennze extend forward and are usually quiet and the wings are folded, at rest on the back. The ovipositor (Fig. 6, 6, c) is exserted from between the right and left halves of the sheath, forming an angle of about 60° with the needle. It is worked into the needle and straightened until as it disappears it forms a right angle with the needle, saw edge forward (Fig. 6, a). The posterior margin of the seventh sternite is membranous and is produced medianly to form a sort of trough (tr) for conveying the eggs into the slit prepared for them. The sides of the trough are supported by a pair of diverging chitinous pieces or more rigid areas. This trough during oviposition is immediately in front of the slit that is being cut and serves as a support to the abdomen, maintaining a constant distance between body and needle and contributing to a rigidity and firmness of the ’ base of the working parts in their relation to the needle. Posterior to the trough and basad of the sheath proper there is a pair of rather small rectangular plates or trowels (t) (Fig. 6, d), one plate at each side, attached to the base of the basal portion of the sheath (sh!) and appearing similarly attached to the base of the lance (le). These plates were observed for the first time in this insect and are not found in Neodiprion lecontei, which belongs to the same subfamily, nor has the writer been able to discover similar developments in sawflies outside of the Diprioninae. The function of these plates or trowels is apparently to support and mold the torn needle fiber into walls and cover for the egg pocket. The sheath (sh! and sh?) is posterior to these plates (t) and its right and left halves cover respectively the right and left sides of the needle at the point of incision. During the sawing there are alternate contractions and expan- sions of the pleurum of the ninth urite which cause the sheath to flex or bend at the juncture of the basal (sh') and apical (sh?) portions, and a side-to-side oblique move- ment of the trough (ir). The saw is worked or dragged until the trough (ir) reaches the mesothoracic legs. The puncture is then complete and the abdomen is slightly ele- vated. The trough (tr) and the trowels (¢) are now pushed back together, smoothing off the torn fiber at the mouth of the pocket and bringing together the walls of the cavity at its opening. The saw is withdrawn at the same time. It is not visible except through the needle tissue, being hidden by the trowel (¢), and its withdrawal is accomplished or accompanied by a backward, upward folding movement. The entire egg-laying process consumes about two minutes. 53373—23—Bull, 1182———2 10 BULLETIN 1182, U. S. DEPARTMENT OF AGRICULTURE. Oviposition occurs over several days, the female going from needle to needle. Table 2 indicates the number of eggs laid and gives an idea of the number of needles upon a tree that are attacked. aide adhe = VI AS Fic. 6.—Diprion simile: Ovipositor. a, Apex of abdomen of female adult in position over nearly com- pleted egg slit (enlarged); 6, thrée-quarters ventral view of apex of abdomen of female adult (enlarged); c, ventral view of portion of egg-laying apparatus of female adult (much enlarged); d, side view of trowel, from ovipositor of adult female (greatly enlarged). TABLE 2.—Oviposition records of Diprion simile. Number of needles oviposited in and number of eggs in each. Total No. SS REGIE PTS Tey OEP Aa OT EN ee ANTE number Host plant. i Ora eee cs i a Dike, Spr Re-type cE Tis 9 | 0 3 9 slit S Sesser ys ace. salaee les cece 26 | Pinus austriaca. PEE Ol eres Ee mere oe beeoe ss smacleetS ltee Semi c crecl aPalaatlec sete 9 | P. laricio. See De hal 11 6 12) ie ei eal heer al Lek 53 | P. sylvestris. 7 ahs 12 pe if OMS Sa eee eee 2 Se ERS aol Sane ce ees athe 27 Do BR 12 2 3 5 12 11 8 2 5 8 68 Do. Gye 5 10 8 6 12 4 13 14 (i 2 81 Do. Of these experiments the first and second were failures owing to the host plant chosen, and the eggs in the third and fourth wae len by virgin females, and therefore will be treated farther on, in consider- ing the experiments on parthenogenetic reproduction in this species. Table 3 shows the length of time elapsing between the emergence of the adult and oviposition. TaBLE 3.—Preoviposition period of adults of Diprion simile. | Time in | | Date Date (days from Mate mee fe Cer Host plant. Remarks. ‘emerged. | tion gence to | ) began. | oviposi- | | | tion. | a | | | | 1...| May 8...| May 9... i h-bamus sylvestris.) 552). 22-22. - =-- 2...| May 11..| May 11..| Wy as. dae 2242) AEB me 3...| May 12..| May 16..| 4| Pinus austriaca....-...........- .| Host plant unfavorable. 4...| May 8.../"May 10-.| 7 Petts Syl VESGEISS 23-2 a2 aa- = =< = | Unfertilized female, eet | maeeea.| Mayli§§ § 2|..... ge2.2-.- eer £5 | 0. 6 | Slat 2 rE AS Co See ...-| New needles attractive. | | ...| June 20.-| June 23..| From the consideration of all the available data the writer is of the opinion that a fertilized female will begin laying eggs soon after fertilization, provided material suitable for oviposition can be found. Such was the case with the first and second females in Table 3. Unfertilized females will begin laying after a two-day period during which they await mating, provided that suitable material is con-. venient, as shown by the fourth and fifth females, which were used in experiments on parthenogenetic reproduction. -22...4- Na ee ee May 2} cil. VPN dees it) sin osl. 4453. Unfertilized female. May 11 to lb........ May 25 to 29....... i, soe ) ART eR. eroee,: Do. i SES pepe | Ses at peli a isis ete: LAs , Bee ae Mae 29935) )_ 42:7 13 | Pinus austriaca ...........-. June 23 to 24....... July 1 to%.......: 8 | Pinus sylvestris.......-....- 1 In counting the number of days in the incubation sat it was assumed that the first eggs laid were the first to hatch and that the latest laid were the latest hatched. a a mil THE IMPORTED PINE SAWFLY. EI ey. BULLETIN 1182, U. S. DEPARTMENT OF AGRICULTURE: For eggs laid about the middle of May (May 9 to 19), from 11 to 14 days were required for development to the point of hatching, aver- aging 12.8 days. For eggs laid in late June, 8 days sufficed for development. Fertilized and unfertilized eggs, apparently, did not differ in the duration of the incubation period. LARVAL DEVELOPMENT. The larve of the imported pine sawfly shed their skins as they develop. The periods between moltings of the larva are called in- stars. The number of instars, the difference in the number between larve producing female adults and those producing males, and the size and appearance of the larve in each of the various instars have been treated under ‘“ Larval instars.”’ Table 5 shows for a number of larve the time spent in each instar, the average length of the instar, and the total length of the larval or feeding period. This table is arranged to show sex and date of hatching of each individual or group of individuals, because the sex makes a difference in the number of instars, and the rate of develop- ment of the larve appears to be accelerated as the season advances. TaBLE 5.—Number and length of larval instars of Diprion simile, showing individual’s date of hatching and sex. | Length of instar. Date egg hatched. Sex. Total. Instar Inst Instar Instar Instar Instar 1 II. III. IV. Vv. Vi. Days. Days. Days. Days. Days. Days. Days. MigyiStore! 2 Lesoisies Male. 6 5 3 6 123) eae ae 32 DD) Qi eee oe alee dors 6 5 4 5 1a eee AP 31 May Olsceko oll dosti 7 5 4 4 Oy adee sche 29 yg ee do 6 4 4 4 ID ceacaeees 29 BOD Oeste? oo tetalec. do 6 4 4 4 10: | cee se Sake 28 Maly 224 sce i(say isete Srorowse oe 7 4 4 6 2 ins jatenerees 23 IMR VED oP ee sakes Sas 2.005525" 6 5 5 4 G.P8ne eees 2 26 Deen as Se te 2 2edoxe ree A 7 tf 5 3: cedgee es 26 Extremes...... douse 4to7 4to7 3 to7 4to6 Ato wes 2ee nue 23 to 32 Average early. dos2a2 6 43 43 42 Sree eeeee 28 TE eo an ee dose 4 5 2 3 TH aaah ae te 16 Average mid- | VOOTE ce fe se elOuee. 4 5 2 3 pl See 16 <= —S——S>| o_O Mig yeO eee: ed Foe kk Female 9 4 5 3 6 *10 37 Maval Zeno. hee ee ee: STAGLOs 5 Mee 6 4 4 2 5 9 30 Opaswnisice nse dacs 0 0 pea as 6 4 4 2 4 9 29 Extremes...... BAA sxe O...........-..| July 3,1916 | July 7, 1916 4 | Aug. 1,1916 25 29 Aederdets-.02:\2i0g..2) 34300. Pre igs A eal Aa as oe Lv ejee ibe 19.5 ADULTS EMERGING THE FOLLOWING YEAR. og RiP Sas Se eed pe Po A | July 9,1917 fr ote Apr. 15, 1918 | Fs NE Re pe 2c Se July 11,1917} July 12)1917 | i ay 2,1918/ 294 | 295 10 | P. monticola...-.._.|..-.4..2.2224.. | June 29,1917 |.......... Apr. 24,1918 | 299 |....20.-.5 11 CS ee Ee ee ee See ee Aor ess. eee May 5,1918 | 310 ja s-< ques aa |? vireiniena 22 0 Rezs dais. 7 t ad, | May 6,1918 | 311 | Bieta 1 es 3 | P. Syiweethis= a. 22 523|52-- 226. ae ast cee ee Motel. ss6.s2b8 28 32 28 32 16 118 16 118 Prepupa (including | pupal period) ..... 10 10 341 341 206} | 29 295 295 Adult period......... 5.8 7.5 5.8 7.5 5.8 7.5 5.8 71.5 | ARCO FF 5 eel | 56. 6 | 62.3 387.6 393.3 58.8 | 62.5 324. 8 328. 5- | 1 Obtained by rule of proportion, as no isolation for length of larval stages gave female adults. The accompanying chart (Fig. 7) gives a general view of the activities. of this species covering a period of about four years, especially the relations existing between stages, broods, generations, and colony periods, and shows the possible opportunities of the species to inbreed and crossbreed among the various colonies, broods, and generations. EFFECT OF METEOROLOGICAL CONDITIONS. The notes on the effects of meteorological conditions on this species. are incomplete and do not lead to any definite conclusions with regard to the part climate will play in its establishment or in the restriction of its range in America. The small number of adults. obtained in the rearing experiments undertaken under the life- history, seasonal-history, and host-plant work gives the impression that the climate of the section of the country where this work was, undertaken, East Falls Church, Va., near Washington, D. C., is rather unfavorable for Diprion simile, while the apparent establish- ment of the species in New England, New York, and New Jersey points to the suitability of a somewhat cooler climate. In the cage work, where the rapidity of development was noted, it was observed to be accelerated by increased temperature. Table 8 records the duration of stages and instars in days for two colonies of Diprion simile between which there was a difference of 46 days in the date of egg laying, and shows the average temperature during each of the stages or instars. THE IMPORTED PINE SAWFLY. 15 TABLE 8.—Effect of time of year and temperature on rate of development of the egg and larval instars of Diprion simile. | | Earlier colony. Later colony. | | Average Average | Stage. s Pv omdll Timein | tempera- gates 1 | Timein | tempera- eer, | Stageor | turein | 598° Or | stage or | turein apart instar. | stage or began | instar. | stage or Die | instar. 4 | instar. } | 1916 Days. oe 1916 | Days. | ahd i= ene tee GG. 2) 3 tii. ast |May 9 13; 61.61 | June 24 | 7 72. 85 Larval instar: | rn See ee SIA 22- 7 68.78 | July 1 40 41325 we ee er 29 4} 64. 50 5 5 72.70 _ |June 2 | 4| 66.25 10 2 77.75 BE a RAST eS 6 6 64. 33 pe 3 79. 00 SESS eee ee 12 | 5 | 67.90 15 | 2! 75.25 ol Se eee i 12 | 70. 46 17 | act 76. 28 a ee a eS Be en ce ee i A Raper to Peon = eee woll -5 Se Se ot eee ae) erie eee ol 66219) |e 22 Re 30 | 74. 51 Some scattered observations record the larve feeding close to the trunk on a cool and rainy day (temperature 60° F., humidity 87 per cent), feeding vigorously and spread out on a warmer and less humid day (temperature 69° F., and humidity 68 per cent), and clustered on needles close to the bole on a still warmer and drier day (tempera- ture 85° F., humidity 40 per cent). These observations would seem to indicate a rather low optimum temperature, somewhere between 69° and 85° F., with a rather delicate responsiveness to any consider- able variation in temperature, and the fact that the larve were observed to be rather slow in developing during a damp period and inactive during a cool, rainy spell (temperature 56° to 71° F. and humidity 85 per cent) tends to show a similar sensitiveness to humid- ity. The observations, however, are too few and were made in too restricted an area to be of much value. PARTHENOGENESIS. Diprion simile can reproduce parthenogenetically; that is, eggs laid ‘ig eis females are fertile and hatch, producing larve which grow, become prepupe, spin cocoons, and finally emerge as adults. All the adults thus far obtained from eggs of unfertilized females, _ however, are males, a result believed usual for parthenogenetic reproduction in sawflies. Females that have not mated appear to wait two days before com- _ mencing oviposition, as shown in Table 3, but after this period passes _ they begin to lay unfertilized eggs. Two of the experiments per- 4 a formed to obtain these unfertilized eggs were successful, one female laying 53 eggs, the other 27. A comparison of the number of eggs laid parthenogenetically with the number laid by a normal fertilized female indicates that the virgin female lays only half as many eggs as _the fertilized female. In the two parthenogenetic experiments in which eggs were deposited about 724 per cent of the eggs hatched, which is approximately the same as the percentage of hatching _ obtained from eggs of fertilized females. The mortality among the 16 BULLETIN 1182, U. S. DEPARTMENT OF AGRICULTURE. * SUP MAK C MUL At SEPT OCT. NOV DET, SGSVE AUC. S¢P7. OCT, NOK \ Q SEPT OC OV. DEC. /G/S i MAY SUNE JULY AUC )WYEE| APR. MIAY SUNE SULY igen APR PIA JUNE \aneeon | OCT. NO. DEC. JAN, 4EB. MAR. | @APR AUC. SEPT. 1 SGI D pril, 1917, and used in experiments during 1917, 1918, and , one emerging from the cocoon in July, 1916, and the other 1919. It shows the division of the adult emergence period into at least two broods, A and B. Two adults in April, 1918, seem to have been somewhat retarded, and these are indicated by a superimposed asterisk. Fic. 7.—Diprion simile: Chart showing in a general way the life history and seasonal history data obtained in studics of two separate lots of Diprion simile material, one received in August, 1915, which was under observation during 1915 and 1916, and the other received in A -/ 7 larvee, however, was higher in the progeny of virgin females, and few | survived to become adults. It may be that larvee wanting male parents are lacking in vitality a , when developing to the adult produce an insect with less viability. This is indicated by the death of a great percentage of the larve under ap- parently favorable conditions and the shorter life of adults from eggs laid by unfertilized females. |PARASITES. Only two species of natural ene- mies were obtained from the experi- ments performed at the eastern field station, East FallsChurch,Va. These were Dibrachys nigrocyaneus Norton and a species of Eurytoma. Britton and Zappe’ record the following: Hymenoptera: Dibrachys ngrocyan- eus Norton, Monodontomerus dentipes Boheman, Drbrachoides verditer Nor- ton, Delomerista n. sp., Cerambycobius sp. (probably new), Hurytoma sp., Hemiteles utilis Norton. Diptera: Exorista petiolata Coquillett. All parasites specifically identified are native species, with the excep- tion of Monodontomerus dentipes Boh., which is a European species already recorded from the United States. Dibrachys nigrocyaneus was rather abundant, much more so than any of the other species, and Britton and Zappe state that only the first three species recorded in their list given above were reared in sufficient num- bers to indicate that they are at all | effective in holding the pest in check. Table 9, from Britton and Zappe, gives the general results of an exam- mation of cocoons collected during | the winter of 1916-17. A short experiment on the length of life of Dibrachys nigrocyaneus Nor- ton was performed. From 65 adults caged without food all the males died within three days and all females * Britton, W. E.,and Zappe, M. P. Theimported pine sawfly. Jn Conn. Agr. Exp. Sta. Bul. 203, p. 273-290, 1917. See p. 283. THE IMPORTED PINE SAWFLY. 17 within eight days; and from 40 adults supplied with cotton soaked in sugar water all the males died within three days, but all the females, except 1, were living on the thirteenth day, and all were not dead until the seventeenth. TaBLE 9.—Cocoons of Diprion simile collected during the winter of 1916-17 and examined for parasites. Condition. ‘Number. | Per cent. ONE eh hi a og ae aoa nine tears enpigess-cisbucn | 1,321 | 41 0 EEA Ee NTS B02 a 8 oe a ST SS AE Eee een 2 Ee eer ee ere Se 1, 210 | 37 ES ee a Se ee ee eee ee ere Cr eee 191 | 6 a Sie ee aU ASS IRN St lie ll dif ook Sed i po. sts 16 Several experiments were made with D. nigrocyaneus Norton, with _ the object of observing oviposition and studying the relation of the _ parasite to this host. All resulted in failure, however, for no parasi- _ tism was obtained, although the chalcids endeavored to oviposit, | usually more than once, in the cocoons supplied. Possibly D. _ nigrocyaneus does not attack Diprion simile in the cocoon stage. _ The presence and activity of these parasites must not lead to the — conclusion that they will bring about an effective natural control of _ Dz. simile. Uf the permanent establishment of this pest is to be pre- _ vented, or if its multiplication and work are to be checked, artificial _ control measures, such as those recommended, must be applied. HOSTS. If the imported pine sawfly is able to feed on a number of species of pine this will be an important factor in the establishment of the species in this country, and it is extremely desirable to know if it can and will use our native pines successfully. Restricted to intro- duced ornamental species of pines, Diprion simile would at worst only become a nursery and estate problem, but if it will attack our Ameri- €an pines it may become a serious forest problem. At present the sawfly seems to be confined to young pines of imported species and has only been recorded from nurseries and estates. To determine the range of host plants which this insect can success- fully utilize, two series of host-tree experiments were conducted. One was to determine the ability of Diprion simile to use a given host suc- cessfully from oviposition to the production of adults. The other was _ to determine the preferred host plants of the sawfly, if there are any. In the first series of experiments a number of adult males and females of D. simile were confined upon a particular species of young pine to observe its suitability. In the experiments on choice of host species a uantity of small native and introduced pines were transplanted into the large screen-wire insectary previously mentioned and a number of males and females liberated within the inclosure. Table 10 gives the results of the experiment to determine the im- i ane pine sawfly’s choice of host plants. Fifty-four male adults and ty-nine female adults of D. simile were liberated in the insectary, ad Lda ihe a 18 BULLETIN 1182, U. S. DEPARTMENT OF AGRICULTURE. into which the following species of young pines had been trans- planted. Number of trees Number of trees Species. placed in insectary. Species. placed in insectary.. PAG ANISUTIACA bod oh oe Oh oes ae 2 2°|“Pinvis ponderosa. 2.22522 .2 (ease 5 PIMUsCeMbTass rex e fet ool eeie 2:3|': Pinus, Pesinosa: At ns ke 3 Binvsdivanieata: 246.52 25 eek oe. Aid Ee EDUEYSEPO DUS d+ = .2 06,26 <1o8ie oe eee 5 TENE Gs Disjei i Cell TT: rae eee Mea UE 2 | Elnus sylyestris.:. <2. 2: eee 15 Ins OttGio. 26 oe cla Ok ae eel, 2 4.) Pus taeda... tod: sce eee i PAIS mon ied ave. So coc a slen 3 | Pinus virginiana). 224 25: ee 3 Twelve species and a total of forty-eight trees. In Table 10 the host trees are arranged according to the number of trees of each species that were chosen by the females for oviposi- tion and the suitability of these pines as hosts is indicated by the number of individuals of the sawfly that were able to develop through the various stages from egg to adult. Frequency of selection for oviposition has been considered a some- what better guide to the appeal of the various pines to the sawfly than the numbers of the different stages of the insect obtained. This is especially true where the number of adults obtained exceeds a third of the total number of larvz, since the larve after hatching were cage-reared, and, although protected from parasites, doubtless | experienced a number of difficulties due to handling and to their artificial surroundings. The species of pines believed most favorable for D. simile are therefore placed at the beginning of the table. TABLE 10.—Experiment to determine the host-plant preference exhibited by Diprion simile. Number Species and serial number of host tree. pepo | Eggs. Larve. | Cocoons.| Adults. chosen. | Pinus sylvesiris, trees 1,20; and 29)... =)... sce tee 3 | lx 13 11 5 strobus;treesin and 62. - ..-...)/. 225 -siseassissece 2a) x 36 29 7 COMIDIAY TIER Zep rinin nonce te eesinw me caw sas siete ye 1 x 12 AA 8 VILETEM ANIA IETES WIA Se Steve sake clatan ate takes 1 x 21 20'| 10 CI VAMIGA ESS EGG Wl wi, bon! Peek sisi re be wdctare ed -- caee le x 14 13 4 TMOMTIGOMDNUNCG ce ets ects wrelee cide e cele ie w aio a toare il x 10 6 | 3 Hexilisntres 2. . ste eee heen eemc es teed 1 x 5 2 | 1 EGA GEOR ON oes ela ate atm aie bt Aas ac ichaa,s 22 oa 1| 8 5 3 1 resinosa; trees 16.and 1822.2.) se2. beck twos 3? 0 QL abe e tees BUSinacn, LCC ee sc 4-\2cse= ciate Ce sae Need ee 8? 0 sy \iatwinjers's Six. cialipto aerate 1 x=number not counted. 2 27 larvee killed—rain. 3?— trees examined and no eggs found. Therefore, while it is possible that eggs may have been over- looked, it is also possible that a larva dropping or knocked from another tree may have reached these; consequently these species can not be given full credit for choice. Table 11 gives a summary of experiments in which adults of Diprion simile were confined in cages on single young trees of certain species of pine. It shows in some degree the greater success attend- ing the use of Pinus sylvestris as a host for the sawfly. THE IMPORTED PINE SAWFLY. 19 TasLe 11.—Experimenis showing the results accompanying the forced use of certain species of pine as hosts by Diprion simile. | Species and serial number of host tree. ace Eggs. | Larvae. |Cocoons.| Adults. Pinus sylvestris: TES 1 -i cs: Sea Sesh oot ppc owe Bae es ooe bee ooeoe ae | Ba A Sioae See ere Ban ater a ome cco ci LEE LE SR Se ee eee eee eee 1 9 3 | D3 ac hoo etek CET EE Tc) hes [GS SS Ee ee ree rer a eee 1 IN 9 I A YS APY |S c5= cli fs OS RS Pe a Peo ee eee 1 79 | 48 | Outs See LEER DLT eee ee eee ee ae 1 53 | 3) || saab coat Sec oe ee oil UL CERES a Sees ee ot 2 ees sree 1 27 | 18 | 2 2 JOR SSS Con 2 ee See ee et ee 1 68 | 2x | 3 1 LP? AD lea ce a ee oe hee ee eee eee WG (hen tee oles Seco |=, clade crite = Pata ate PTE, 51 5 A Ea Se ee eee es Se eee eee a 1 9 ay | 2 1 ODD St 2. 51 See ee Dee ie Soca ko An) Saai5 eas a ctl | Sod auc eas |ce scsi che aes ee. ot JERS oi doa SSB eae ee ey oe oe 2 6 5 eee wrasse warpdana, tro 10.5.2 5. :-------------b.--62--% Br sade acy | eee ae |. Poy eeu. Se ee oe Pinus austriaca: Tce ata tera t Coo e ose cceceocedecsns AE] Soe a crete cn a tne Sa ere Soe ee eae ees ea ot 8 ES en ee eee ee 1 26 tees lee HaSee See S lo Aisi Ee ee eee 10 Speer | ee re | bs a nana eae rs PTV LTOR JO), 32/42) 5-2 o-oo ee DPS Loe Rane Le Peetas Maisie. shales ee UR Se oe ee eee ea eee, | a reenact aera EN a el Sha Ses 2S RIMESH ALCON ELOR be Jo ous od ssoe = ans see o 3 Hos. 5 oe crete 3 9 a eoo ees ee nek cee laine eaente Pinus strobus: © L jo toi eae: ee Mele ee eee 2 13 | 7 BRA Weald 5 Gye Me SE Gea eee 1 29 OHS actece St ae oe 1 N=needles in which eggs have been deposited but the number of eggs not counted. 3 x=number not counted. Britton and Zappe,’° in their paper on this species, give the follow- _ ing list, in which the pines are arranged “ according to the preference shown by the sawflies in nature and to the largest number of sawilies reaching maturity” in their host-plant experiments: Pinws-erreaa. Wall. - Bhotan pine... ...2-'.55--<,-~ Peus eemora tann. Stone pine../........2.--.- Pinus flerilis James. Limber pine............... Five-needled pines. Pynesistroous Iann, White pine... ...... 02.4215. Pinus koraiensis Sieb. & Zucc. Korean pine...... Pinus montana Du Roi. Mugho pine............ Pinus densiflora Sieb. & Zucc. Japanese red pine. Prunus tesinosa-Ait.;< Red pine. 90. 252 25.2 ES Pinus sylvestris Linn. Scotch pine.............. Two-needled pines. Pinus ponderosa Dougl. Bull pine............... Pinus laricio Poir. var. ausiriaca Endl. Austrian nae Nolet > alo) ae ee abe. oS aieiclo «les elas eic.s 2 .oha Preetareomoa Mau) 6 Pitch. Pines. 3 si. sie hina $5 oe Three-needled pine. This list shows that Diprion simile has a decided preference for _ the five-needled and the softer two-needled pines. A comparison of this list with the writer’s experiments shows an agreement as to the preference for the five-needled pines and the apparent lack of suitability and attraction possessed by P. laricio, P. austriaca, and P. ponderosa, but a disagreement regarding P. sylvestris, which was a favored tree and capable of carrying the species from egg to adult in the writer’s cages, while, along with P. ponderosa and P. laricio variety austriaca, it was almost immune to infestation in the experiments of Britton and Zappe. _. From these data it seems reasonable to suppose that Diprion simile 1s capable of utilizing several of our American pines as hosts and therefore may succeed in establishing itself in the forests of the United . { : 10 Britton, W. E., and Zappe, M. P. Op. cit., p. 278. ne ee ee a - 20 BULLETIN 1182, U. S. DEPARTMENT OF AGRICULTURE. States. Furthermore, the species of pines represented above are from sufficiently different sections of the country to make available a possible host in most of our pine-growing regions and in such a variety of climates that some of them must be favorable for the insect’s development. DISTRIBUTION IN THE UNITED STATES. Diprion simile is known to occur in nurseries in Connecti- cut, New York, Penn- sylvania, and New Jersey. Specimens have been received from Massachusetts, and the species is re- corded from Indi- ana." The history of the sawfly in the United States suggests that it was introduced with imported nur- sery stock, a view which is supported Fic.8.—Diprion simile: Distribution in the United States. A round by the fact that in black spot indicates a report from a definite locality: a square Connecticut, New spot indicates occurrence in the State, but without definite locality. Jersey, and Massa- chusetts it has been intercepted at quarantine inspection ports. The following list gives the localities from which the species is recorded (see also Fig. 8): Connecticut: Derby, Greenwich, Hartford, New Canaan, and New Haven." Indiana. Massachusetts. New Jersey: Elizabeth, Rutherford, and South Orange.” New York: Flushing, L. I. Pennsylvania: Chestnut Hill !* and Penbrook. ECONOMIC IMPORTANCE. The imported pine sawfly is to be regarded as an extremely danger- ous visitor in the United States, because in Europe, where it is asso- ciated with Diprion pina L., the two are responsible for an immense amount of damage. D. ee has usually been considered the chief | but t cause of this injury, e two species are so closely allied '* and so frequently confused that the presence of D. simile in this country must be regarded with apprehension. In Europe D. pini * is accred- ited with serious damage to pine in southwestern Russia, in 1914 de- foliating many acres of pine in the districts of Achtyr and Izium; in Germany, in Prussia, and particularly in Brandenburg and Silesia, in 1 Britton, W. E., and Zappe, M. P. Op. cit., p. 275. 12 From a letter from Harry B. Weiss, dated Aug. 12, 1916. 13 Localities for specimens determined by S. A. Rohwer. 14 Diprion simile Hartig has been considered a synonym of J). pini L. 1s Britton, W. E.,and Zappe, M. P. Op. cit., p. 276. OS ee oC. et wien THE IMPORTED PINE SAWFLY. 21 1914; in France, in 1906; in Sweden; in Norway, in 1914, when the larve nearly defoliated 10-year old pines on one plantation; and in England, where they are said to injure Scotch fir as well as pine. In many of these infestations D. simile doubtless took a prominent part _ and in some instances may have been the chief depredator. Should D. simile become permanently established in this country, it will be capable of great destruction. At present it is probably confined to nurseries and estates, where it is doing sufficieit damage to attract considerable attention, and nurserymen and gardeners are _ endeavoring to exterminate it. CONTROL. In the United States the seeming preference of Diprion simile for young trees makes this sawfly primarily a nursery pest and a nur- sery problem rather than a forest problem. This confinement to trees 1n nurseries and on estates is of considerable advantage in an attempt to eradicate or control the species, since in such situations the best opportunities for combating it are found. The infestation is more easily observed early in its course, and methods of control can be employed which, despite their effectiveness, couid hardly be recommended to check a forest invasicn, owing to the inaccessibility and vastness of the area. Because infestations of the sawfly are at present limited to young trees in nurseries and under similar condi- tions, it is doubly important to combat it now, first, to check its rav- ages, and, second, in the hope of exterminating it or at least pre- venting it from ever becoming established in our forests. In the effort to control the species its life-history and seasonal- history advantages, already referred to, should be taken into con- sideration and strict watch maintained against its appearance or reappearance. Infested trees should be sprayed with some stomach poison, such as a mixture of lead arsenate and water in the proportion of 2 pounds of powdered arsenate of lead to 50 gallons of water, or, in smaller quantities, 6 teaspoonfuls of the powder to 1 gallon of water. A knapsack, barrel, or tank spraying outfit, whichever is available and convenient to use, should give good results. Hand picking and dropping or shaking the larve into pails partially filled with kerosene, crushing them with the hands protected by leather gloves, and knocking or jarring them from the trees and treading on them, are all possible methods of control, especially where labor can be obtained cheaply. Such methods as these have been used successfully in Europe. ORGANIZATION OF THE UNITED STATES DEPARTMENT OF AGRICULTURE. November 12, 1923. DECKEEOTY Of, AGTICULUTE. oo hciclc hace seine Ss + = © Henry C. WALLACE. WERSUNIMIEL SECTCHEIU cha rs ewe eee os ee wee Howarp M. Gore. Weer Of SCIEMMULC WOTk. sc nstacee cs cen ec se E. D. Baa. Director of Regulatory Work. 2 oo.6. cee. oes WALTER G. CAMPBELL. wwerior.of; hatension Works... <: oss2 Uy »® a) _ — _——" a ee oe Canes aioe ‘ 7 be ¥ ee > ~ ea te De BS 1. = : ie os - or hy : . i nat > a 7 i w f a > rt : 7 7 ite) aes ate " . > : by a i! 7 lett ied 7 i Reh J P a 7 et Th, A i Go _ et) ; pa: 4 rity cy WP ing ie 4 “i Sar Nie he ae ms ah patie 7 .) i rr sy 4 i ’ 7 : ‘ ee a a A IE ce — —_— ee an — = — _ — i — 22 Se ee eee ea ee oe eee t = * a - v : aoe 2 — an) ” P 7 is