CABBAGE APHIS. 



175 



is that of the Aphides, or Plant-lice. We know their 

 general appearance well on Roses and Hops, Beans or 

 Cabbage ; and there seems to be hardly a forest, or 

 fruit tree, or crop plant in this country, of which we 

 can say that it is not infested by one or more kinds of 

 Ai^hides, either above or under ground. 



We know Aphides, in a general way, as small soft 

 insects, having a head furnished with a beak, which 



^ 

 ^ 



lA^^'J 



Fig. 136. — Cabbage Aphis : 1 and 2, male ; 3 and 4, wingless female ; 

 nat. size and magnified. 



is often half as long as the body, sometimes quite as 

 long, or longer ; the horns are commonly long and 

 thread-like. The abdomen ends in a sharp, or curved, 

 or variously formed tip, and often, but not always, 

 bears on its upper part, near the end, a pair of horn- 

 like tubercles, long or short, as the case may be. 

 These tubercles are really hollow tubes, known as 

 cornicles ; what their use may be is not clearly known. 

 Some have considered them part of the breathing 

 apparatus ; but, from the most recent and careful 

 observations published, they appear to be additional 

 means of excreting fluid. 



The Aphis larvae, sometimes known as lice, are 

 much like their parent, only wingless; the pupas have 

 the beginnings of wings. In the perfect state — that is, 

 where there is the fullest amount of development — 

 there are males, and winged and also wingless females; 



