266 M. W. R. de V. GRAHAM 



MELANCISTRUS gen. n. 



Derivation : Greek ayxicrrpov, hook ; [i.eXacr, black. Gender : masculine. 

 Type-species : Tridymus mucronatus Thomson, 1876a : 194. 



Occiput not margined. Clypeus marked off from the face by a weak groove, its anterior 

 margin strongly curved. Both mandibles with four teeth. Antennae inserted below the 

 middle of the face but above the level of the ventral edges of the eyes, 12-segmented (11262 in 

 male, 11 253 in female) ; first funicular segment longer than the pedicellus. 



Pronotum short, without a collar. Mesoscutum and scutellum having their surface uneven, 

 reticulate and also with numerous small piliferous tubercles, hence appearing almost rugulose. 

 Notauli complete, deep. The scutello-axillar sutures are straight and converge strongly to- 

 wards the mesoscutum, so that the base of the scutellum is only about one fifth the breadth of 

 the mesoscutum. Scutellum hairy, except its sides and the frenum ; frenum marked off by a 

 weak grooved line. Axillae hairy, except laterally. Propodeum with a median carina which 

 is crossed at about the middle of its length by a transverse crest or ridge which in profile appears 

 like a tooth ; plicae and nucha absent ; callus hairy all over right to the edge of the meta- 

 pleuron, the bases of the hairs giving it a roughened appearance, convex, with a raised tubercle 

 in the middle ; spiracles small, nearly circular, close to the hind margin of the metanotum. 

 Postspiracular sclerite broad, sometimes with indications of an oblique carina. 



Dorsal surface of hind coxae roughened, with indications of a longitudinal crest, hairy along its 

 whole length. Hind tibiae each with two spurs, the second weaker and about half the length of 

 the first. Fore wing with no hyaline break between parastigma and marginal vein ; marginal 

 vein longer than the curved stigmal vein ; postmarginal vein variable, from slightly shorter 

 than to slightly longer than, the marginal. 



Gaster compressed laterally, strongly so in female and strongly carinate ventrally ; hypopy- 

 gium of female very long, its tip situated at about three quarters the length of the gaster, and 

 provided with a membranous process or mucro (Text-fig. 201). 



Melancistrus is close to Gastrancistrus Westwood, from which it differs by the 

 following combination of characters. 



Propodeal callus hairy all over as far as the edge of the metapleuron, convex and 

 with a raised tubercle in its middle ; median carina of propodeum strongly raised, 

 crossed at about the middle of its length by a transverse crest which in profile 

 appears tooth-like. Dorsal surface of hind coxae with indications of a longitudinal 

 crest, and hairy along their entire length. Gaster of female with the hypopygium 

 extending far caudad, with a membranous mucro. Body black, or black with a 

 very weak bluish tinge. 



In females of Gastrancistrus species, the hypopygium is shorter, reaching at most 

 about half way along the gaster and lacks a mucro. 



Gastrancistrus coxalis Thomson approaches Melancistrus in the structure of the 

 propodeum and has the hind coxae hairy dorsally ; but in coxalis the propodeal 

 callus has only a weak tubercle, the median carina of the propodeum is not raised 

 and is not trans versed by a crest, the dorsal surface of the hind coxae has no 

 longitudinal crest, whilst the body is metallic green. 



In facies Melancistrus much resembles Oxyglypta Forster ; but in that genus the 

 sculpture of the mesoscutum is composed of transverse ripples or striae, both 

 mandibles have 3 teeth, the median carina of the propodeum is neither raised into a 

 tooth medially nor traversed by a crest, whilst the hypopygium of the female gaster 

 lacks an apical mucro. 



