XXIII GALL-FLIES 523 



After what we have said as to the mode of nutrition of parasites 

 it will be understood that the physiological conditions of life 

 may not be so different in a gall-dweller and a parasite as would 

 at first be supposed ; and it is perhaps not a matter for much 

 surprise that good characters cannot be found to separate the 

 gallicolous from the parasitic forms. 



Fam. I. Cynipidae Gall-flies. 



Wings tvith very fevj cells, ivith no dark patch {stigma) on the 

 anterior margin ; pronotum fixed to the mesonotum, and at 

 each side extending hack to the point of insertion of the 

 front tving. Antennae not elhoived hut straight, composed of 

 a moderate number {1^2-15) of joints. Early stages passed 

 either in galls or as parasites in the hodies of other Lisects. 



The Cynipidae are always small, frequently minute. Insects ; 

 usually black or pitchy in 

 colour. The simple struc- 

 ture of the antennae and 

 the number of their joints are 

 of importance as an aid in 

 identifying a Cynipid. The 

 mesonotum is usually re- 

 markably convex, and has, 

 behind, a prominent scutel- 

 lum, which more or less over- 

 hangs the small metanotum 

 and the median segment ; 

 these are perpendicular in their direction ; the sculpture of these 

 posterior parts of the alitrunk is usually deep and remarkable. 

 The abdomen has usually only a short petiole, so as to be pseudo- 

 sessile ; but there are some genera in which this part is rather 

 long. The abdomen is generally so very much changed in outer 

 form that its structure is not easily understood. The visible por- 

 tion is frequently in larger part made up of the greatly enlarged 

 dorsal plate of the second or third segment, or of both. These 

 large plates are really chiefly composed of free flaps, and on lift- 

 ing them up the large ventral plates are disclosed, although these 

 appeared previously to be nearly or quite absent. In the female 



Fia. 346. Neuroterus lenticularis. Britain. 



