THE GRAPE PHYLLOXERA IN CALIFORNIA. 



85 



Fig. 8. — Phylloxera vitifoliae: Types of antenna of 

 intermediates. Greatly enlarged. 



eyes were absent, and in no case were ocelli discernible. In most in- 

 dividuals there were two sensoria on the last antennal joint, and in 

 one antenna there were two small basal sensoria and the usual 

 apical sensorium, making 

 three in all. The basal sen- 

 soria were not in any case 

 as large as those of the 

 winged migrant. The an- 

 tennae and legs were about 

 as long as those of the 

 nymph, noticeably longer 

 on the average than those of 

 the individuals of group 2, 

 which in turn were longer 

 than those of the two indi- 

 viduals of group l. 10 It would appear, therefore, that greater devel- 

 opment of wing pads and compound eyes is complemented with a 

 lengthening of legs and antennae and a tendency to bear the extra 

 sensorium of the winged forms. The femora exceed the tibia? in 

 length. 



There is among the intermediates a tendency toward asymmetry. 

 This was remarked in Italy and has also appeared in California. 



One eye may have more facets than the 

 other ; the lengths of antennae and legs 

 may differ in individuals, those of one 

 side being longer than their counter- 

 parts, and one antenna may possess 

 more sensoria than the other. 



In two instances the fourth stage of 

 intermediates was observed in Califor- 

 nia. In one case an individual of group 

 3 molted from what appeared, under 

 the lenses of the binocular microscope, 

 to be a true nymph. In the other case 

 an example of the same group molted 

 from an insect which itself resem- 

 bled a nymphical; in fact, after the 

 molt the individual did not appear 

 to have changed its structure at all. 

 In both fourth and fifth instars the 

 wing pads were large and "fleshy." 

 From three individuals, all of group 3, eggs were obtained. These 

 eggs could not be differentiated from eggs laid by wingless radici- 

 coles. One nymphical deposited two eggs, which were lost. An- 



10 The insect depicted in figure 7 is considerably less enlarged than that represented in 

 figure 6. 



Fig. 9. — Phylloxera vitifoliae: Nymph 

 and antenna of newly molted in- 

 sect, for comparison with interme- 

 diates. 



