SUB-FAMILY ALLOTRINA. 233 



longitudinal furrow on the mesosternum. The scutel- 

 lum is separated from the mesonotum by a transverse 

 furrow, and it may also have one or two fovese at its 

 base. The abdomen is sessile or subsessile, short, 

 ovoid, not much if at all compressed, and shorter or 

 at least not much longer than the thorax. 



They are small species (from 1 to 2 mm. in length), 

 with short ovoid bodies, seldom pilose except on the 

 median segment and base of abdomen. So far as we 

 know, all the species live parasitic ally on Aphidae, or 

 on the parasites (Aphidius) of aphides. It is true 

 that Hartig records having bred several species from 

 Nematus gallicola ; but from my own observations I 

 can say positively that this is an error : they really 

 came from aphides which had crept into the galls. 

 When an aphis has been attacked by an Allotria it be- 

 comes fastened to the leaf, turns brown or cream- 

 coloured, the Allotria remaining inside of it until it 

 reaches the perfect state. No cocoon is spun, the 

 skin of the aphis serving for one. It is possible that, 

 as suggested by Mr. Gr. 0. Bignell, some of the species 

 may be hyperparasites, feeding not on the aphides, 

 but on their parasites (Aphidius). In that case the 

 Allotrina must be regarded as injurious insects. 



Undernoted is a list of the hosts of those Allotrids 

 which have been bred. 



Allotria castanea, Htg., aphis on Papaver somni- 



ferum. 



circumscripta, Htg., aphis on Raphanus ; 

 also on Aphis pini on 

 Chaerophyllum sylvestre, 

 and from Aphis ribis 

 (Kirchner). 



erythrothorax, Htg., aphis on Prunus, and on 

 Aspidiotus rosas, Be. 



flavicornis, Htg., aphis on Cinthamus tine- 

 torius. 



forticornis, Gir., aphis on Pinus pumilio. 



