74 



BULLETIN 903, U. S. DEPARTMENT OF AGRICULTURE. 



eyes show their red pigment and soon become prominent. Legs and 

 antennas are relatively long, and the femora exceed the tibiae in 

 length. At all times the rows of tubercular areas on the dorsum are 

 well marked. During the nymphal instar the insect shows a very 

 considerable growth; the newly molted individuals are quite flat, 

 but full-grown nymphs are roughly cylindrical. 



DESCRIPTION OF STAGES. 



The nymph or pupa, full grown. 

 PI. XI ; text fig. 9, p. 85. 



General color orange or orange yellow ; anterior part of mesothorax and 

 inesosternuni whitish, or at least always noticeably paler than the rest of body. 

 Antennse pale yellow, extended but little beyond anterior margin of prothorax. 

 Compound eyes and ocelli dark red ; former composed of large number of facets. 

 Head and abdomen bearing 4, thorax 6 longitudinal rows of dark tubercular 

 areas (coarse roughening of epidermis), each surmounted by a spine; wing pads 

 dark gray, grayish black, or rarely jet black; legs pale yellow, often with a 

 dusky cast ; abdomen with 7 visible segments, mesothorax apparently bisected by 

 a transverse fold ; beak very pale yellow, reaching to posterior coxae. 



Measurements of 6 individuals are given in Table XXV. 



Table XXV. 



-Measurements of nymph of the grape phylloxera, 

 Creek, Calif. 



Walnut 



Individual No. J 



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. 

 1.102 



Mm. 



Mm. 

 0. 3295 



Mm. 



0. 1500 

 .1464 

 .1419 

 .1438 

 .1089 



Mm. 



0. 1366 

 .1384 

 .1321 

 .1304 

 .1071 



Mm. 



Mm. 



0. 0402 

 .0350 

 .0331 

 .0332 

 .0339 

 .0295 



Mm. 



0. 1536 

 .1545 

 .1455 

 .1455 

 .1179 

 .1184 



Mm. 

 0. 0223 







0. 0339 



.0224 



2 



.889 





.3600 



.0230 









.0254 



3 



.957 



.507 



.3339 



.0321 

 .0304 



.0223 





.0232 



4 



.851 



.798 



.725 



1.121 



1.197 













5 



.511 



.2695 



.1389 



.1252 



.0315 



.0309 



.1577 



.0198 



6 





7 



.558 

 .569 















8 





























1 Individuals 1,7, and 8 at end of stage; 4, 5, and 6 at beginning of stage; 2 and 3 about middle of stage 



Newly molted nymphs average about 0.78 mm. in length and ma- 

 ture nymphs about 1.1 nun. The nymphs are always more active 

 than the immature wingless forms, wandering larvae excepted. Their 

 eyes are well developed, as in the winged insect, and they have the 

 ocelli found in that form. The third joint of the antennse bears a 

 single sensorium corresponding to the apical one of the migrant, and 

 as the last molt approaches the migrant antennse show through the 

 nymphal skin, and thus the nymphal antennae appear to bear two 

 sensoria. 



