DESCRIPTIONS OF NEW TAXA IN THE THORONINI (HYMENOPTERA, PROCTOTRUPOIDEA, SCELIONIDAE)

Abstract A generic diagnosis of Microthoron Masner is completed, and the male antenna is figured. Data on distribution and variability of M. baeoides Masner are presented. M. miricornis n. sp. ♀ is described from South India. A key to the known species of Microthoron is given. Thoronidea taino n. gen., n. sp. ♀ is described from the Dominican Republic. Thoron longicornis n. sp. ♀ is described from Arizona, and a key to the known species of Thoron Haliday is given.

The members of the tribe Thoronini, egg parasites of aquatic Heteroptera, are generally poorly represented in collections. However, we are inclined to believe that this is largely due to the cryptic niches in which the adult wasps are encountered and also to lack of adequate collecting techniques in such situations. Yellow pan traps situated close to fresh waters have proved to be successful in collecting Thoronini (Masner 1972(Masner , 1976b. Similarly, the pitfall traps used for trapping various terrestrial arthropods often contain high numbers of miscellaneous proctotrupoid wasps (unpublished data). The use of ethylene glycolwater mixture (1:l) with small amounts of unscented detergent as a surface breaker in both pan traps and pitfall traps cuts considerably the frequency of servicing the traps (10 days to 2 weeks). Glycol prevents decomposition and inflation of specimens. Pan traps must be roofed with sheets of clear plastic and the scooped contents carefully rinsed in water before dumping in alcohol. Students of proctotrupoid wasps are hereby strongly encouraged to use this simple yet highly rewarding method of collecting. Masner 1972, Microthoron Masner, Can. Ent. 104: 847. 1976a The generic diagnosis by Masner (1972) is amplified by the following:

Microthoron baeoides Masner
This species has a surprisingly wide distribution. In addition to the type series from Malaya, we examined specimens from E. and S. India (the holotype of Acolomorpha indica Mukerjee), Rhodesia, and the Cap Verde Islands (W. Africa). All specimens seem to be conspecific but there are some differences, which may be correlated to variations in length of body. The Cap Verde specimens are slightly larger and have A3 somewhat longer than in other specimens. The length of the postmarginal vein is variable as well as the colour of antennae and legs. The cephalic proportions are also subject to variation e.g. total lengthlwidth ratio and the shortest width of frons compared with width of eyes. There are two (8 ? ) specimens from The Gambia (Abuko Nature Reserve, Lamin, 25 Jan. -1 Feb. 1978, pan traps, L. Huggert) which we prefer not to assign to M. baeoides. They differ from the latter by having vertex slightly carinate and female scape and flagellum light yellow in contrast with the black clava. The antenna of the male is discussed in the generic diagnosis (Fig. 6).
BIONOMICS. Although the hosts are unknown it is likely that species of Microthoron attack eggs of some semiaquatic Heteroptera (e.g. Gelastocoridae, the toad bugs). This is assumed from the known host relations of other Thoronini, as well as from the circumstances under which the specimens of Microthoron were collected. The Gambian and the South Indian specimens were collected in pan traps (along with specimens of the genus Tiphodytes Bradley, egg parasites of the Gerridae) on muddy ground close to fresh waters. The type series of M . baeoides was collected in Malaise trap set near a stream; two species of Tiphodytes were also present. Female. Length 0.8 mm. Black; legs including coxae bright yellow, tibiae and tarsi yellowish brown; radicle and proximal 2/3 of scape yellowish, apical third of scape and A2-A6 brownish; mandibles and palpi yellow; prosternum light brown; wings only slightly infuscate.
Metasoma distinctly more elongate ( BIONOMICS. The unique female was caught in a pan trap with a specimen of Tiphodytes (known egg parasites of Gerridae). The host, however, remains unknown. DISCUSSION. This is certainly a very unusual species. We prefer to classify it in Microthoron, despite the strange antenna and relatively slender metasoma.
ETYMOLOGY. The name refers to the admirable shape of the antennae.

KEY TO SPECIES OF Microthoron (females)
(1) A3 lanceolate with obtuse apex, 4 times as long as A2, longer than either scape or clava; clava spindle-like (Fig. 4); metasoma distinctly elongate, more than twice as long as broad (Fig. 1); legs including coxae yellow; S. India A3 only slightly elongate, at most twice as long as wide, subequal to A2, much shorter than either scape or clava; clava ovoid (  Female. General habitus as in Microthoron, i.e. short and plump; body almost entirely smooth and shiny, with only small areas sculptured.
Head strongly transverse, wider than mesosoma; occipital carina complete and strong; ocelli in very low triangle, lateral ocelli almost contiguous with inner orbits; eyes rather large, densely hairy; subocular suture deep, percurrent, flanked by fans of striae both below and above, i.e. cheeks heavily striate; clypeus small, truncate at apex, with anterolateral corners subacute; mandibles short, strong, tridentate, with teeth equal; radicle not conspicuously elongate; antennae 7-segmented, clava massive and not distinctly segmented.
Mesosoma short, strongly arched dorsally, gibbose; skaphion present, flexed and almost vertical if viewed laterally; notauli absent; scutellum almost semicircular; metanotum medially with distinct bulge overlapping middle part of propodeum; in dorsal view only posterolateral corners of propodeum visible; pleura with chains of crenulae; mesopleura with sharp carina extending from middle coxa to merge with suture connecting tegula with fore coxa; wings rather narrow, with long marginal cilia; fore wing with submarginal vein running very close to fore margin in basal 3/4, remote from the latter only in front of marginalis; stigmalis longer than either postmarginalis or marginalis; hind margin of fore wing in basal l/3 with strong frenal gutter; legs slender; spurs 1,1,1; tarsi 5-segmented.

TYPE-SPECIES. Thoronidea taino n. sp. (described below).
ETYMOLOGY. The generic name stresses the placement of the new genus in the tribe Thoronini (Scelioninae).
REMARKS. Thoronidea most closely resembles Microthoron (see key below). The well defined carina on mesepisternum extending from middle coxa in Thoronidea is similar to those in Thoron and Neothoron; however, the structure of the metasoma in Thoronidea is identical with that in Microthoron and similar to those in Tiphodytes and Tanaodytes. Thoronidea is also convergent with Idris but can be easily distinguished from the latter by presence of skaphion, glossy sculpture of the body as well as the structure of metasoma (broad laterotergites, etc.).
Mesosoma with notauli wider and deeper than in metallicus, distinctly crenulated at bottom; posterolateral corners of propodeum not prominent, posteromedian part of propodeum less reduced and thus more visible than in rnetallicus; in lateral view anterior part of mesoscutum less arched (Fig. 9c); metanotum with distinct erect sharp spine (Fig. 9b); lower part of pronotum above fore coxa roughly rugulose-foveolate; metapleura and propodeum less hairy than in rnetallicus, part of metapleuron above hind coxa virtually glabrous; marginal vein in fore wing narrower than in metallicus, i.e. pseudostigma almost wanting, postmarginalis very fine, shorter than stigmalis (15:20); area of basal vein with angular pigmented streak; coxae rather elongate, hind coxae distinctly twice as long as wide, hairy dorsally on apical half.

August 1979
FIGS. 8-9. 8 , Thoron metallicus Hal. 9 (8a, apex of metasoma in lateral view; 8b, profile of mesosoma and TI; 8c, head and antenna). 9, Thoron longicornis n. sp. 9 (9a, apex of metasoma in lateral view; 9b, profile of mesosoma and TI; 9c, head and antenna). BIONOMICS. It is reasonable to assume that this new species is parasitic in eggs of Curicta S t 3 (Heteroptera, Nepidae). The latter genus replaces the genus Nepa L. in the South and South-west of USA (Hungerford 1922). Curicta sp. was collected by R. Sternitzky (specimen in CNC) in the summer of 1967 at the type locality of Thoron longicornis. On the other hand, Thoron metallicus was reared from eggs of Nepa cinerea L. in Europe (Ferrikre 1916;Henriksen 1918) and its probable host in the eastern Nearctic is the only North American species, Nepa apiculata Uhler (Brooks and Kelton 1967).
DISCUSSION. The two known species are compared in the description of T . longicornis and distinguished in the key. The rather long postmarginal vein as well as angular pigmented spot in the fore wing of T . longicornis are superficially reminiscent of the Neotropical genus Neothoron Masner. The latter genus, however, is distinct from Thoron primarily in the different structure of the propodeum, the unarmed metanotum, and the position of the lateral ocelli.
KEY TO SPECIES OF Thoron (The European T . gibbus Ruthe is not included, as it is probably identical with T . metallicus (cf. Masner 1972) .) (1) Apex of scape extending well above vertex (Fig. 9c); in dorsal view temples about half as long as an eye, rather straight; A4 twice as long as wide; postocciput smooth, with no arched ridges; hind coxa hairy dorsally on apical half; metapleura with a glabrous spot above hind coxa, coxae yellowish; metanotal spine semierect, sharp, without pilosity (Fig. 9c); TI not humped dorsally, costate all over; apex of T7 in female not upcurved (Fig. 9a) Apex of scape extending at most to level of vertex (Fig. 8c); in dorsal view temples subequal in length to an eye, rather arched; A4 about 1.5 times as long as wide; postocciput with about 4 distinct arched ridges on each side; hind coxa without hairs dorsally; metapleura and propodeum uniformly hairy, coxae blackish; metanotal spine less erect, blunt, concealed with pilosity (Fig. 8b); T I distinctly humped dorsally, more or less smooth at top; apex of T7 in female distinctly upcurved (Fig. 8a)