456 FRUIT INSECTS 



There may be six generations of the root-inhabiting form 

 annually, and experimental rearing has shown that reproduction 

 may continue in this way for several years without appreciable 

 loss of vigor or of proHficness. Normally, however, during 

 the latter half of the season some of the hce infesting the roots 

 become more elongate than the others and have longer legs 

 and antennae. These forms do not become mature at the third 

 molt and begin to lay eggs, but continue their development; 

 at the fourth molt, wing pads become visible on the thorax ; and 

 at the fifth and last molt, which takes place after the nymph 

 has crawled to the surface, functional wings are acquired. 

 After waiting a few hours for the wings to dry and the body to 

 harden, they take flight and, if a wind is blowing, may be trans- 

 ported a considerable distance. After feeding about a day on 

 the under side of one of the tender leaves at the end of the shoots 

 they are ready to deposit their yellowish-white eggs of two 

 distinct sizes; from the larger eggs are developed the true 

 females and from the smaller ones the true males. Both sexes 

 are wingless, and the female after fertilization deposits a single 

 so-called winter egg on the bark of tlu^ older canes. These 

 sexual forms are much smaller than the others, and functional 

 mouth parts are lacking. The insect does not pass the winter 

 exclusively in the egg state, ])ut many of the younger individuals 

 of the root-inhabiting form, as W(41 as many of the later migrants 

 from the leaves, hi])(Tnate in small groups on the larger roots. 



The winter eggs hatch in the spring soon after the first grape 

 leaves have become well expanded, and the young hce normally 

 crawl up the canes to the leaves, where th(\y settle on the upper 

 surface and Ix^gin sucking out th(^ juices of the leaf. The 

 puncture ma(l(^ in feeding stinuilatc^s the growth of the leaf 

 cells so that a hollow gall is fornKul, i)rojecting from the under 

 side of the leaf and opening by a narrow slit on the upper 

 surface (Fig. 390). The opening is guarded by a dense growth 

 of down. Within this cavity the insect continues its develop- 



