Hymenoptera 273 



sessile. The joint between the first and second 

 abdominal segments is very complex and allows great 

 mobility, so that the hind-body with its ovipositor or 

 sting can be readily turned in any required direction. 

 The larvs of all the Petiolata are white, legless 

 maggots, provided in some way with food by their 

 parents. 



Cynipidae. — The CynlpiJa or Gall-flies are very small Hymenop- 

 tera usually black or dark in colour. The feelers with twelve to 

 fifteen segments are thread-like and straight. The pronotum is small 

 dorsally, but embraces the mesonotum on either side as far back as 

 the base of the forewing; the mesonotum has a large convex scutellum 

 which partly covers the metanotum and propodeum. The wings have 

 no stigma and only two or three longitudinal nervures and a single 

 cubital cell. The trochanters are two-segmented. The abdomen is 

 very complex in structure; the third and fourth tergites are large and 

 convex, and overlap those behind them to a great extent. The slender 

 ovipositor of the female with toothed tips to its borers can be with- 

 drawn into the abdomen and partly coiled. The majority of the 

 larvje of the Cynipida; live in galls on plants, due to the irritation set 

 up by the act of egg-laying, or by their own presence in the plant- 

 tissues (see below, pp. 303-4) ; the gall of each species is of 

 characteristic form — the " oak-apple " is a well-known example. But 

 some Cynipid larvje live as inquilines or " cuckoo-parasites " in the 

 galls due to the activity of other species. Others again are parasitic 

 on the larvae of other insects. The Cynipidse are universally distributed 



(157)- 



Kvaniidse. — The Evaniida are a small family of Hymenoptera 

 distinguished by the insertion of the second abdominal segment 

 (" stalk ") of the hind-body on the dorsal aspect of the first (pro- 

 podeum). The feelers are straight and thread-like, with thirteen or 

 fourteen segments. The wings have few nervures and the trochanters 

 of the legs are two-segmented. The larvs live parasitically on other 

 insects ; the females of the genus Evania lay their eggs in the egg- 

 cases of Cockroaciies (3). 



Ichneumonidse. — The IchneumonidiE or Ichneumon-flies are an 

 exceedingly large family. The feelers are long, straight and many- 

 jointed, tapering towards the tip ; three ocelli are always present on 

 the crown. The wings have for the Hymenoptera a complex 

 neuration ; a distinguishing character is the presence of tw^o cells 

 between the cubitals and the second posterior cell (at the anal angle of 

 the fore-wingj (fig. 149/"), Rarely wings are quite absent. The stalk 

 of the elongate hind-body is attached to the lower or hinder aspect of 

 the first abdominal segment, which is very large, while the metathorax 

 is relatively short, so that the middle and hind pairs of legs are inserted 



S 



