REVISION OF THE NEARCTIC SPECIES OF TRICHACIS FOERSTER (HYMENOPTERA: PROCTOTRUPOIDEA: PLATYGASTRIDAE)

Abstract The Nearctic species of the genus Trichacis are revised. Nine out of 15 species recognized are new to science: T. alticola (New Mexico, Colorado), T. bison (Ontario, Florida, Louisiana, Illinois, Texas), T. celticola (Mississippi, Ontario, Louisiana, Texas), T. dracula (Illinois), T. elongata (Missouri), T. huberi (California), T. mandibulata (Illinois), T. pyramidalis (Ontario), and T. striata (Florida). Six previously described Nearctic species are redescribed, viz. T. arizonensis (Ashmead), T. cornicola (Ashmead), T. cornuta Fouts, T. rufipes Ashmead, T. texana Fouts, and T. virginiensis Ashmead. The males of T. arizonensis, T. texana, and T. virginiensis are described for the first time. A generic diagnosis of Trichacis and keys to Nearctic species are given. The higher classification, bionomics, world distribution, and character states of Trichacis species are discussed. Résumé La taxonomie du genre Trichacis de la région néarctique est revue. Des 15 espèces incluses dans le genre, nous décrivons 9 nouvelles espèces : T. alticola (Nouveau Mexique, Colorado), T. bison (Ontario, Floride, Louisiane, Illinois, Texas), T. celticola (Mississippi, Ontario, Louisiane, Texas), T. dracula (Illinois), T. elongata (Missouri), T. huberi (Californie), T. mandibulata (Illinois), T. pyramidalis (Ontario), et T. striata (Floride). Les six autres espèces, viz. T. arizonensis (Ashmead), T. cornicola (Ashmead), T. cornuta Fouts, T. rufipes Ashmead, T. texana Fouts, et T. virginiensis Ashmead sont redécrites, et les mâles de T. arizonensis, T. texana et T. virginiensis sont décrits pour la première fois. Nous pourvoyons une diagnose du genre et un tableau de détermination des espèces néarctiques. La classification supraspécifique, la biologie, la répartition géographique mondiale et la polarité de transformation des caractères des espèces du genre Trichacis sont discutées.

The genus Trichacis, proposed by Foerster (1856) for several Palearctic species, was at first not properly recognized in North America. Ashmead (1893) described two Nearctic species in Synopeas Foerster and Isorhornbus Foerster respectively. At the same time (1893), however, he described under the name Trichasis (emendation for Trichacis) two species now classified in Metanopedias Brues, and earlier (Ashmead 1887) one species, now also considered to belong to the latter genus (Masner and Jackson 1966).  concept of Trichacis was blurred with that of Metanopedias; he also could not define satisfactorily the limits between Trichacis and Isocybus Foerster, believing that the two genera intergrade. Muesebeck and Masner (in Krombein and Burks 1967) and Masner and Muesebeck (1968) recognized six Nearctic species in Trichacis. Muesebeck (in Krombein et al. 1979) again catalogued the six Nearctic species considered to belong to Trichacis.
The members of Trichacis may be recognized among all genera of the Platygastrinae by having a specialized area with a tuft of fine dense erect hairs on the top of the scutellum. This tuft is rarely situated below the apex of the pointed specialized area (T. arizonensis, T. pyramidalis). Other generic character states encountered in members of Trichacis are the smooth frons, receding temples behind eyes, non-abrupt 3-5 segmented antennal clava in females, as well as 6 visible tergites in female metasoma. By contrast, the members of Isocybus may have scattered erect hairs on the scutellum, not organized in a dense tuft, frons with more or less rugulose sculpture, temples behind eyes full or even slightly bulging, as well as a distinct 6-segmented antennal clava in females. Similarly, the members of Metanopedias should be distinguished at once from those of Trichacis by the absence of a specialized area and no erect tuft of hairs on the scutellum in both sexes, as well as by the metasoma in female with fewer than 6 visible tergites. In addition to the above character states Trichacis and Metanopedias could also be distinguished by fundamental differences in structure of the antennae in both sexes. However, the latter character is not clearly visible under lower magnification due to the minute size of antennomeres 3 and 4 in members of Metanopedias. Trichacoides Kieffer can be easily distinguished from Trichacis in having the scutellum covered with numerous tiny spines and with no tuft of hairs, and tergite 2 almost entirely striate longitudinal:^. Kozlov (1970) classified Trichacis in the tribe Platygastrini of the Platygastrinae. He stressed the non-spinose scutellum as well as the antenna1 clava in female not distinctly 4-segmented as commonly encountered among the members of the tribe Synopeadini. In my opinion the above criteria are hardly exclusive, with numerous exceptions on both sides. I prefer to keep Trichacis in the tribe Platygastrini based, however, on the two following character states, viz. the palpal formula 2-1 and the tibial spur formula 1-2-2. The members of the tribe Synopeadini appear to have the palpal formula 1-1 and the tibial spur formula 1-1-1. There seems to be also a good biological character as a criterion of tribal classification, viz. a remarkable vernal seasonality of most Trichacis species, shared with other members of the Platygastrini. The Synopeadini seem to have an autumnal peak of occurrence, although slightly less pronounced than the almost exclusive vernal peak of the Platygastrini. The above difference in relative seasonality of members of the two tribes may be caused by association with two different groups of cecidomyiid hosts.
The recorded world distribution of Trichacis comprises the entire Holarctic region, with seven species in Europe (Kieffer 1926), and with six species in North America (Muesebeck in Krombein et al. 1979). Recently, more species were described from Europe (SzelCnyi in SzCkessy 1953;Szabo 1977); however, the species described by SzelCnyi appears to belong to Isocybus and the four species described by Szabo are difficult to interpret because of inadequate descriptions and superficial figures. Trichacis is also well represented in the Neotropical region though no species were formally described from south of the United States. I examined numerous undescribed species in the Canadian National Collection from Mexico, Costa Rica, Guatemala, Panama, Brazil, Colombia, Ecuador, and Peru. One species was described from the Oriental region (Java) and one from the Australian region (Lord Howe Is.). The placement of the latter two species in Trichacis remains problematic as types were not available for examination and no other members of Trichacis were encountered in materials from the Old World tropics.
All members of Trichacis are probably primary parasites of various gall midges (Cecidomyiidae) though only a few reliable host records are so far available. The best studied species is the Palearctic T. rernulus (Walker), a monoembryonic parasite of Mayetiola spp., pests of wheat and oats (Marchal 1906;Gahan 1933). The first instar larva is cyclopoid, the following two instars are segmented hymenopteriform larvae. T. rernulus and possibly also other species of Trichacis are important agents in biological control of pests. Very little is known about association of Trichacis species with plants through their respective cecidomyiid hosts. Ashmead (1893) and  listed T. cornicola (Ashmead) associated with dogwood in Missouri. T. arizonensis (Ashmead) is currently recorded from Ephedra sp. in California.
All Nearctic species of Trichacis studied are predominantly to strictly vernal, with only one generation per year. Members of some species are frequently caught by sweeping on both herbaceous plants and shrubs or trapped by Malaise and interception traps. The Nearctic species of Trichacis are encountered in biotopes of various altitudes, from lowlands and hills to the alpine zone in the Rocky Mountains. An interesting correlation exists between the development and pigmentation of wings of platygastrid wasps and the altitude of the biotope (Masner 1981). With the increasing altitude the wings are progressively longer and darker, reaching the extremes among the species from high Andes (around 4000 m) in South America. The only Nearctic species that displays this striking feature is T. alticola recorded from altitudes 2000-3000 m in New Mexico and Colorado. Several lowland species of Nearctic Trichacis (e.g. T. celticola, T. virginiensis) show wings with various degrees of infuscation but the length of the wings is normal.
By the time this study was undertaken the number of Nearctic species of Trichacis had increased from 6 to 15. Nevertheless, this significant increase is considered only a beginning of yet another phase of research. Vast areas of the North American continent, harbouring potentially many new species, remain virtually unexplored. New collecting methods (e.g. screen-sweeping) aimed at amassing whole populations rather than a few individuals should accelerate the above process of species recognition, study of problems of variability, etc. Fouts' (1924) material did not exceed 30 specimens; the present paper is based on 1129 specimens. Detailed biological studies linking Trichacis species to their respective hosts as well as host plants are urgently needed. The correct association of sexes could be achieved only through careful rearings. The role of Trichacis species in biological control of pests should also be explored.
A classification of the Nearctic species of Trichacis into species groups is not attempted at this time. The present knowledge is considered to be rather incomplete, with many important data not available.
The Nearctic members of Trichacis appear to be a morphologically very homogeneous complex. Relatively few characters appear to be diagnostic; therefore, the descriptions of species are focused on a restricted number of character states. Useful cephalic characters appear to be: general shape and lengthtwidth ratio of head, with cephalic measurements from dorsal view (head termed transverse if wider than long); mutual ratios of eye heightlinterorbital space, with measurements from frontal view, where eye height is measured from lowermost to uppermost point of orbit and the interorbital space is the shortest distance between inner orbits; length of scape, measured excluding the radicle; mutual ratios of OOLILOL; shape of mandibles and teeth; shape of processes on temples; female antenna, especially the type of clava and the location of the sensilla on clavomeres; male antenna, especially the shape of A4. The number of sensilla and their exact location on female clavomeres appear to be highly species-specific. However, the sensilla are often deeply embedded in receptacles with only the tips protruding beyond the outline of the clavomeres. This will pose difficulty in observing them even on slides, under a high magnification of a compound microscope. In some species the sensilla are virtually invisible from the dorsal view since they are both deeply embedded in receptacles and the latter ones are located below the curvature of the clavomere (e.g. in T. celticola Masner). The use of phase contrast is recommended while observing the almost transparent sensilla on slide mounts.
The mesosoma offers relatively fewer diagnostic characters than the head. However, the shape of scutellum in peculiar in two, and the wings are characteristically infuscated in three species.
Useful diagnostic characters of the metasoma are: lengtwwidth ratio of T1; total lengtwwidth ratio of metasoma; shape and lengtwwidth ratio of T6 in female; sculpture of base of T2; microsculpture of T3-T6.
The measurements are figured in direct readings of an ocular scale at 160 X ; they represent fractions of 1 mm, with 100= 1 mm. Direct readings are preferred over w:l ratios to permit mutual comparisons of length and width of individual parts of the body (e.g. length of scape vs. interorbital space).
The morphological terms and their respective abbreviations used in this paper are those proposed by Masner (1 980). Mid-to large size (1.3-3.0 mm) platygastrid wasps, with body moderately to distinctly elongate. Body black, legs and antennae often bright orange-yellow, wings usually clear but infuscated in several species. Head transverse, subellipsoidal or subrectangular; mandibles bidentate, with teeth subequal, rarely the lower tooth longer; clypeus not protruding; palpal formula 2-1 ; cheeks not striate, without subocular suture; antennal process not prominent; frons predominantly smooth, at most with scattered punctures mainly along inner orbits; ocelli in a low triangle, OOL equal to or slightly shorter or longer than LOL; eyes glabrous or with scattered hairs; temples behind eyes protruded into points or hornlike structures in several species; hyperoccipital carina developed in most species at least in its middle part; antennal formula 10-10, in female clava 3-5 segmented, non-abrupt, clavomeres with 1 sensillum each; in male A4 modified as sex segment; mesosoma arched, cylindrical, about as wide as high; notauli and anterior parallel lines well developed in most species; scutellum moderately to acutely arched, smooth, in posterior half with a specialized area filled with dense compact hairs forming a tuft or brush erected at an angle less than 90°, rarely tuft flanking pointed glabrous part of scutellum wedged between two isolated hairy areas, thus giving impression of spinose scutellum; mesopleuron without depression, with at most indication of sternaulus in its anterior part, generally glabrous, with only few scattered hairs; metapleuron and propodeum densely pubescent; propodeum medially with 2 parallel keels; fore wing veinless but often with rudiment of submarginal vein, usually indicated by darker pigmentation; marginal cilia of fore wing moderately long; hind wing veinless; tarsal formula 5-5-5; tibia1 spur formula 1-2-2; T1 with only sparse hairs, not covered with dense, compact pilosity; T2 largest of all tergites, with 2 hairy pits situated anterolaterally, with anteromedian part glabrous and in most species shortly striate; metasoma in female with 6, in male with 7 visible tergites; ovipositor sheaths in female not exposed.
Anterior parallel lines fine, surrounded by coriaceous sculpture in anterior third of mesoscutum; notauli almost percurrent, obliterate in extreme anterior part; specialized area of scutellum almost heart-shaped, moderately elevated, with rather broad tuft of hairs; fore wings long, greatly surpassing apex of metasoma. Metasoma moderately elongate; T2 anteromedially (between pits) smooth and flattened; combined length of T3-T6 shorter than width of T2 (4155); posterior margin of T2 and entire T3-T6 with dense fine punctations.
Male. Differs from female in structure of antenna (Fig. 24) and metasoma; wings are slightly longer than in female (Fig. 25). Distribution. Canadian zone of SW USA (New Mexico, Colorado); however, the real range of this species is expected to be considerably wider in the SW USA, possibly also in the adjacent mountainous parts of Mexico.
Biology. Unknown; the type series was collected in an aspen grove. Variability. Only little variation was observed. The body length may vary from 1.5 to 2.2 mm in both sexes.

Remarks.
T. alticola is a very distinct species among all Nearctic members of Trichacis because of its long scape exceeding the top of vertex, the long wings widely surpassing tip of metasoma, and A8-A10 in female antenna distinctly longer than wide. The name alticola (in Latin) refers to the occurrence of this species at high altitudes. T. alticola is the only Nearctic species of Trichacis that exhibits the typical correlation of excessively long and dark wings with its high altitude habitat. Head transverse (30:60); occiput smooth and glabrous medially, with fine coriaceous sculpture and hairs at sides; temples behind eyes unarmed, coriaceous, and hairy; postgenae smooth and almost glabrous; hyperoccipital carina sharp, strongly developed; OOL distinctly shorter than LOL (7:9); frons smooth, under high magnification (160 X ) with delicate transverse microsculpture below posterior ocelli, with few fine transverse wrinkles above antennal process and toruli; EH < IOS (25:38); antennal process short, truncate; mandibles clasped, with teeth subequal; antenna (Fig. 15) short, with 5-segmented clava, AGA10 with sensilla.

Trichacis arizonensis (Ashmead)
Anterior parallel lines inconspicuous; notauli almost percurrent, abbreviate only in extreme anterior apices; anterior scutellar pits unusually large and deep; scutellum in lateral view (Fig. 34) cone-shaped, pointed, with specialized area situated below and behind the point; fore wings shortly surpassing apex of metasoma.
Male (hitherto unknown). Similar to female except for structure of antennae (Fig.  19) and metasoma.
Anterior parallel lines distinct; notauli abbreviate in anterior third; scutellum moderately arched, with specialized area heart-shaped, tuft of hairs broad, dense; fore wings slightly surpassing apex of metasoma.
Male. Similar to female except for structure of antennae (Fig. 20) and metasoma; fore and mid legs (except darker coxae) orange-yellow.   1-1.8 mm). The colour of the legs may be considerably lighter, particularly in males. The points above the eyes tends to be smaller in smaller individuals. The occiput medially may have coarser sculpture than in the holotype. Remarks. T. bison can be distinguished from T. cornuta by having the points on the temples situated immediately above upper orbits of eyes (frontal view). From T. dracula it may be distinguished by much smaller temporal points. The name of this new species refers to the American buffalo (Bison).
Anterior parallel lines delicate; notauli abbreviate in anterior third; scutellum rather arched, with specialized area heart-shaped, cone-like elevated, covered with dense tuft; fore wings slightly surpassing base of T6, i.e. apex of metasoma exposed.
Male. Similar to female but differs in structure of antenna (Fig. 18) and metasoma; fore femur and tibia light brown. Biology. Host unknown; apparently associated with cecidomyiids injurious to hackberry (Celtis). Variability. The body length varies slightly. The shape of metasoma in the female is variable due to partly telescoped T3-T6; T6 in particular may vary from slightly shorter than wide to 1.5 times longer than wide. Fore wings tend to be more clear and less distinctly patterned in individuals from Ontario than those from Mississippi. Remarks. The individuals of this species are the most robust of the Nearctic species of Trichacis. Trichacis celticola may be also recognized by the fore wings not exceeding the tip of metasoma in female, furthermore by A7-A10 in female with deeply sunken sensilla, and by the remarkably patterned wings in both sexes. The name of this new species refers to its presumed association with hackbeny (Celtis). Fig. 2 1893, Synopeas cornicola Ashmead, Bull. U.S. natn. Mus. 45: 286, 288. 1924, Trichacis cornicola: Fouts, Proc. U.S. natn. Mus. 63: 17, 18. 1979 Female. Length 1.50 mm. Black; legs brown, trochanters, fore femora and all tibiae brown, mandibles, radicle and base of scape yellowish brown, distal part of scape and A2-A10 uniformly brown; wings clear.
Anterior parallel lines delicate; notauli abbreviate in anterior third; scutellum rather low, with specialized area almost heart-shaped, moderately elevated, with short tuft; fore wings slightly surpassing apex of metasoma.
Male. Similar to female except for antennal structure and metasoma; legs considerably lighter than in female, yellowish brown, with coxae and hind femora darker.  Variability. Legs considerably lighter in individuals from qorida. Also in the type series appendages much lighter due to age of the material.

Remarks.
Individuals of T. cornicola can be distinguishecl from those of T. rujipes by considerably shorter metasoma, unpunctured frons as well 8s by T3-T6 with only very delicate punctures. Female. Length 1.40 rnrn. Black; A1-A6 and legs in greater part brown, antennal clava, coxae and femora darker; wings clear.
Anterior parallel lines delicate but distinct; notauli short, better indicated only in posterior third of scutum; scutellum moderately arched, with specialized area very small, almost heart-shaped, moderately elevated, with short tuft; fore wings slightly surpassing apex of metasoma.

Distribution. Texas.
Remarks. Trichacis cornuta can be conveniently recognized among all Nearctic species of Trichacis by the points on temples situated below the level of upper orbit of the eyes.
Male. Differs from female in structure of antennae and metasoma; combined length of T3-T7 only slightly shorter than width of T2 (4651). Variability. The combined length of T3-T6 in females may vary, also the length of T6; consequently, wings may reach the apex of metasoma in individuals with shorter metasoma. Remarks. Individuals of T. elongata are the longest among all Nearctic species of Trichacis. Trichacis elongata is closely related to T. ruJipes but differs from the latter by more elongate metasoma in both sexes; the transverse striae above antennal process are much more developed in elongata than in rujipes, and so is also the hyperoccipital carina. The name of this new species refers to its remarkably elongate shape of body. 9. T. huberi n. sp. Female. Length 1.7 mm. Black; legs and antennae predominantly dark brown, knees, apices of fore tibiae and all tarsi light brown; wings clear.
Male. Unknown. Female. Length 1.4 mm. Black; legs and antennae dark brown, fore tibiae, all trochanters and tarsi light brown; wings clear.
Male. Similar to female, differs in antennal structure (Fig. 17) and metasoma; legs distinctly lighter than in female, fore and mid legs predominantly yellowish brown.

Distribution. Illinois.
Biology. Unknown. Variability. Fore and mid legs lighter brown in some female paratypes. Remarks. Trichacis mandibulata shares the same type of mandibles with T. texana and T. pyramidalis, however, differs from both in structure of female antenna, structure of metasoma in both sexes, as well as in colour of antennae. The name of this new species refers to its remarkable mandibles. 11. Trichacis pyramidalis n. sp.
Anterior parallel lines delicate but distinct; notauli abbreviate in anterior fifth; scutellum in lateral view cone-shaped pointed, with specialized area pointed prominent, partly obscured by thin tuft (Fig. 33); wings surpassing apex of metasoma.
Male. Similar to female except for structure of antenna (Fig. 16) and metasoma; antennae uniformly bright yellow throughout.
Type material. Holotype Q (CNC No. 17678), Canada, Ontario, Point Pelee National Park, June 9 1968, Malaise trap; allotype 13, with same data as in holotype but caught May 19; paratypes: 109 Q 8 6 , with same data as holotype, caught in May or June 1968 (CNC); 1 Q paratype, same locality as above but caught May 29 1979, L. Masner (CNC). Distribution. Ontario. Biology. Unknown. Variability. The occiput may be more coarsely rugulose in some individuals; the specialized area of scutellum is less elevated in some paratypes. Remarks. Trichacis pyramidalis is undoubtedly closely related to T. texana because of the similarity in antennal structure and in the shape of the mandibles. These two species may be distinguished by the shape of the scutellum, which is sharply pointed apically in pyramidalis and only slightly elevated in texana. The name of the new species refers to the pyramidal shape of its scutellum (in lateral view).

Figs. 9 , 21
Material examined. Lectotype P (USNM No. 2277), VIRGINIA, Arlington; allolectotype 8, and 2 9 P paralectotypes with same data as on lectotype (USNM); numerous individuals examined from following provinces and states: New Brunswick, Ontario, Quebec; Arkansas, Arizona, Florida, Georgia, Louisiana, Maryland, Missouri, North Carolina, Tennessee, Virginia. Distribution. Widespread common species ranging from Florida to Maritime Canada, also Arkansas and Arizona in southwestern USA. Biology. Host unknown; a vernal species flying from April in the lower austral zone and May-June in more northern regions; rarely individuals encountered in late summer and fall indicating a possible second generation. Variability. A highly variable species. Total body length varies considerably, from 1.30 to 2.40 mm. Variability of several character states seems to be correlated to length of the body; in smaller individuals the sculpture of the occiput is finer, the transverse striae above the toruli are less developed, punctation of T3-T6 is finer, and antennomeres in both sexes are shorter, e.g. the clavomeres in female are more transverse. Metasoma may be longer or shorter in some individuals, thus determining the degree by which it is surpassed by fore wings. Coloration of antennae and legs may vary in females from bright orangeyellow to predominantly light brown. Remarks. Trichacis rufipes appears to be related to T. elongata, T. striata, and T. huberi. It is closest to T. elongata from which it may be distinguished by shorter metasoma, finer striae on frons, sculpturing and shape of anteromedian area of T2 as well as by weaker hyperoccipital carina.
Mesosoma longer than high (70:45), with very distinct patch of yellowish dense pilosity in anterolateral comer of pronotum, and a smaller patch in ventral comer of pronotum (above fore coxa); anterior parallel lines delicate; notauli deep, almost percurrent, abbreviate only in extreme anterior comers; scutellum rather flattened, with specialized area small, almost heart-shaped, moderately elevated, with short tuft; fore wings barely covering tip of metasoma; mesopleura with distinct, dense, (predominantly) horizontal striations over all.