318 REPORT OF TILE COMMISSIONER OF AGRICULTURE. 



eyes and ears. The weather had been very warm previously, and as 

 late as the middle of November the plants in the turnip -fields around 

 the city were swarming with the lice. 



LIFE HISTORY. 



Common as the insect is, its life history has not been fully worked 

 out. But two forms have been observed by Buckton and Thomas — the 

 winged and the wingless viviparous females. Curtis described what he 

 took to be the winged male, but from his description it is evident that 

 he mistook all winged females for males. Fitch follows him in this 

 error, in that he uses the following sentence taken almost word for word 

 from Curtis without credit to that author: " In August, September, and 

 October the old wingless females are seen, resting stationary, with their 

 bills inserted into the leaf, pumping out its juices, surrounded by their 

 young brood all similarly employed, with here and there a winged male 

 walking lazily about over the backs of his kindred." After this state- 

 ment Fitch recognized Curtis's mistake, and says : " The winged individ- 

 uals, Mr. Curtis takes it for granted, are males; but they certainly are, 

 at least for the most part, females, and show the tip of the ovipositor 

 slightly projecting, like a tail, from the end of the body. So we may 

 safely say that neither the male nor the oviparous female is known. 



The wingless viviparous female has a rather long oval body, covered 

 with a whitish mealy coat. When this coat has been removed by im- 

 mersion in alcohol or otherwise, the body is seen to be of a grayish- 

 green color, with eight black spots down each side of the back, increas- 

 ing in size towards the posterior end. The antennae are green, with 

 black tips, and are shorter than the body, and the eyes, legs, and tail 

 are black. (PI. VII, Fig. 4, b.) 



The young when first hatched are oval, shining, bright yellow in color, 

 and lack the mealy coat. 



The winged viviparous female is yellowish-green, with the eyes, head, 

 neck, and thoracic lobes black, and the antenna} and nectaries dark 

 brown. The legs are dusky-brown and hairy ; the tail is dark-green or 

 brown and also hairy ; the wings are rather short, with stout, coarse veins 

 and dark stigma. (PI. VII, Fig. 4, a.) 



NATURAL ENEMIES. 



Concerning the European natural enemies of the Cabbage Aphis, 

 Buckton says (ibid.): "Several species of Syrphida? and Ichneuniouidse 

 act effectively as checks upon the increase of A. brasakec. The larva) 

 of the former Dipterous dies, living in the midst of such plenty, soon 

 gorge themselves and become of great size. Amongst the latter Hy- 

 menopterous parasites may be mentioned several genera of aphidi- 

 vorous Ichneumons, as Ceraphron, Trionyx, and Coruna. A common form 

 is a fly, which appears to be Trionyx rupee Curtis. In September, often 

 nine-tenths of a colony will be struck by this parasite, the aphides, in- 

 stead 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 individual." 



Similarly in this country we have many natural enemies of this aphis, 

 and among them an Ichneumouid, which is very closety allied to and 

 almost identical in appearance with the Trionyx rupee just mentioned. 



