66 



BULLETIN 903, U. S. DEPARTMENT OF AGRICULTURE. 



Table XVI gives measurements for four individuals of the second- 

 instar radicicole. 



Table XVI. — Measurements of seeond-instar radicicoles of the grape phylloxera, 



Walnut Creek, Calif. 



Individual No. 



Length 

 of body. 



Maxi- 

 mum 

 width 

 of body. 



Length 

 of beak. 



Length 

 of hind 

 femur. 



Length 



of hind 



tibia. 



Length of antennal joints. 



Length 



of sen- 



sorium. 



1 



2 



3 



1 



Mm. 



0.419 

 .448 

 .439 



.499 



Mm. 

 0.234 



Mm. 

 0.154 



Mm. 



0. 0625 



.0624 



Mm. 



0. 0526 



.0518 



Mm. 



0.0190 



.0205 



Mm. 



0. 0204 



.0205 



Mm. 



0. 0586 



.0589 



Mm. 



2 





3 



.257 

 .270 



i .113 



.168 





4 













0. 0171 









\" 









i Telescoped. 



The roughened tubercular areas on the dorsal surface are more 

 conspicuous after the first molt, and a rapid increase in bulk is 

 apparent during the second instar. 



The second, third, and fourth molts occur at practically equidistant 

 periods. Under highest temperatures and optimum food conditions, 

 these instars are passed in about two days apiece. Under a tempera- 

 ture of 58° F. from three to eight days elapse between molts, the 

 average being about five and one-half days. 



Table XVII gives the measurements of five individuals of the 

 third instar. 



Table XVII. — Measurements of third-instar radicicoles of the (jrape phylloxera, 



Walnut Creek. Calif. 



Individual No. 1 



Length 

 of body. 



Maxi- 

 mum 

 width 

 of body. 



Length 

 of beak. 



Length 

 of hind 

 femur. 



Length 



of hind 



tibia. 



Length of antennal joints. 



Length 

 of sen- 

 sorium. 



1 



2 



3 



1.. 



Mm. 



0.592 

 .524 

 .522 

 .649 



Mm. 



0.303 

 .312 

 .332 

 .355 



Mm. 



0.178 

 .164 

 .179 



.155 



Mm. 

 0. 0699 



Mm. 

 0. 0607 



Mm. 



0. 0202 



.0252 



Mm. 



0. 0321 



.0207 



Mm. 



0. 0616 



.0568 



Mm. 

 0.0 



2. .. 



.0144 



3 



.0739 

 .0732 

 .0758 

 .0741 



.0622 

 .0687 

 .0660 

 .0692 





4... 



.0241 

 .0197 

 .0206 



. 0205 

 .0187 

 .0194 



.0634 

 .0589 

 .0598 







.0177 



5... 



.648 



.371 



.145 



.0186 



6 



.0190 























1 Individuals 1-3, newly molted; 4, two days after molt; 5, three days after molt. 



During the third instar (PL X, a, b, c) the increase in bulk con- 

 tinues rapidly. The dorsal tubercular areas are larger than in the 

 previous instar, but in color and shape no differences appear. 



Table XVIII indicates the measurements of seven individuals of 

 the fourth (penultimate) instar. 



