i6o INJURIOUS AND USEFUL INSECTS 



grapes do not fill out, and their skin is wrinkled. When the 

 roots of a vine which exhibits these symptoms are closely 

 examined, very numerous swellings are found upon them, 

 and small grains, like yellow dust, are seen adhering to them. 

 A lens shows that the yellow grains are Aphis-like insects, 

 which pierce the bark of the root by their long beaks, and 

 suck up the juices. The outline of the body is oval, and the 

 back rounded. The head is not easily distinguished, for it 

 conforms to the general outline ; but closer inspection enables 

 us to recognise it by the small, reddish eyes, the three-jointed 

 antennae, and the long suctorial beak. The legs are short, 

 and the tarsus has at first one, afterwards two, joints. No 

 waxy or sugary exudations are produced. The insects in 

 this stage are active for two or three days, but then drive 

 their beaks into the roots, and move no more. They moult 

 thrice, and attain maturity in about three weeks, when each 

 lays about thirty unfertilised eggs, from which, as a rule, 

 young are hatched which altogether- resemble their parents. 

 Thus the generations succeed one another rapidly during 

 the summer months, and the number of individuals increases 

 at a portentous rate. As summer declines, the root-feeding 

 insects die, but a few survive in a torpid condition till spring, 

 when they swell, burst along the back, and emit a number 

 of young individuals of the same form as themselves. It is 

 in the root-infesting stage that the Phylloxera causes most 

 injury to the vines. 



In late summer a second form appears in vast numbers, 

 which is distinguished from the first by gradually acquiring 

 wings, and also by minor changes of form. The compound 

 eyes become much larger, the legs longer, the body more 

 elongate, and numerous, regularly-arranged tubercles appear 

 on the dorsal surface. Both the wingless and the winged 

 form proceed from precisely similar eggs, and it is probable 

 that when fresh hatched, they do not differ perceptibly. The 

 second form is apparently related to the first as a pupa or 

 late larva, with more or less developed wings, is related 

 to the larva fresh from the egg. It has a beak or suctorial 

 proboscis as in the earlier stage, the transition from one to the 

 other being apparently effected by additional moults and 

 intervening periods of growth. The wings, which are the 

 distinctive additions, first appear as minute external rudiments, 



