84 



BULLETIN 803, U. S. DEPARTMENT OF AGRICULTURE. 



Fig. 



6. — Phylloxera vitifoliae: Intermediate of 

 type 2, ventral view. Much enlarged. 



fore visible from above. In group 1 were two individuals collected 

 on young vinifera vines. One of them greatly resembled an adult 



wingless radicicole, but be- 



sides the larval eyes it had 

 two to three extra facets, and 

 the antennae and legs were 

 longer than in the radicicole. 

 The other was slender, re- 

 sembling a prenymph in 

 shape, and had about six ex- 

 tra eye facets, and one an- 

 tenna showed two sensoria. 

 Group 2 (fig. 6) had six rep- 

 resentatives, all with small to 

 very small rudimentary wing 

 pads invisible from above. 

 In all cases the antennae (fig. 

 8) and legs were long, and 

 one insect had two sensoria 

 on antennal segment III. In shape the individuals resembled wing- 

 less radicicoles. One specimen (from Wyoming Red) had no extra 

 eye facets, and the others from young viniferae had a varying number, 

 usually 10, although one had about 15. The remaining 9 individuals 

 came under group 3 (fig. 7), 

 and, because of their more pro- 

 nounced nymphlike characters, 

 these are more easily observed 

 in life upon roots than are 

 those of the other two groups, 

 and 4 of the 6 individuals rec- 

 ognized alive on roots were of 

 this type. 



It is probable, judging from 

 random collections, that the 

 insects of groups 2 and 3 are 

 about equally abundant and 

 each somewhat more so than 

 those of group 1. All the in- 

 dividuals of group 3 had rudi- 

 mentary wing pads, in many 

 cases almost as large as the wing 

 pads of the nymphs. They bulged out from the sides of the insects, 

 and were soft and appeared coiled (fig. 7) or curled. The com- 

 pound eyes were well developed, there being from 66 to 100 per cent 

 as many facets as in the nymphal eyes. In some cases the larval 



Fig. 7. — Phylloxera vitifoliae: Intermediate of 

 type 3, ventral view, much enlarged ; an- 

 tenna at right, more enlarged. 



