APHIS CRATiEGI. 35 



sometimes, weight for weight, there is more animal 

 than vegetable substance present. The leaves then 

 become putrid, offensive in odour, and quite disgusting 

 to the eye. 



Several species of Syrphldce and Ichneiimonidm act 

 effectively as checks upon the increase of A. hras- 

 sicce. The larvae of the former dipterous flies, living in 

 the midst of such plenty, soon gorge themselves and 

 become of great size. Amongst the latter hymeno- 

 pterous parasites may be mentioned several genera of 

 Aphidivorous ichneumons, as Ceraphroii, Trionyx, and 

 Coruna. 



A common form is a fly which appears to be Trionyx 

 rapce^* Curt. In September often nine tenths of a 

 a colony will be struck by this parasite, and the 

 Aphides, instead of passing from their pupa state into 

 the imago, will turn brown and hard from the deadly 

 action of the grub, which solitarily inhabits each indi- 

 vidual. 



The ichneumon which finally emerges is pitchy brown, 

 with four or five yellowish abdominal rings. The 

 antennse are 16-jointed, including the basal member. 

 There are 5 joints in the tarsi, the fifth of which is 

 more than twice the length of the fourth. 



A figure of this insect (PL XLVI, fig. 7) is added to 

 those oi Aphis hrassicce, from which the simple character 

 of the wing- venation can be most easily seen. 



Aphis crat^gi, Kalt. Plate XLVII, figs. 1 — 3. Kalt. ?, 

 Walk., Koch ?, Pass. ? 



Apterous viviparous female. 



* Vide Curtis, ' Farm Insects,' p. 73, and Curtis, ' Guide to Gen. 

 Ent.,' p. 547. 



