WALNUT APHIDES IN" CALIFORNIA. 



21 



individuals of this generation of which the date of deposition had 

 been ascertained. Individuals of the fourth generation probably 

 mature in an average of 16 days. The leaves of the Eastern black 

 walnut fall earlier than those of the European or Calif ornia black 

 types, and consequently the viviparous aphides are not found so late 

 on the trees. There are probably not more than nine generations of 

 these in a year. 



Immediately after passing the final molt the aphides begin depos- 

 iting young. These are entirely pale lemon-yellow with red eyes 

 and four longitudinal rows of capitate hairs and do not exceed 0.70 

 mm. in length. From 10 to 20 young are produced by a single female, 

 dependent on the season of the year. The earlier generations are 

 more prolific. After midsummer the progeny becomes smaller and 

 smaller with successive broods. 



THE PUPA OP THE WINGED VIVrPAKOTJS FEMALE (FIG. 9). 



After the second molt the pupal wing pads are apparent as small 

 emarginations on the sides of 

 the thorax, but after the fol- 

 lowing molt they are much 

 more readily seen. The pupa 

 of the winged viviparous female 

 may be described as follows.: , 



Color generally pale lemon-yellow, 

 sometimes white; head often with a 

 reddish tinge. Antennae on small 

 frontal tubercles, pale yellow, with 

 the filament and articulations of joints 

 3 to' 6 dusky black. Eyes bright red. 

 Thoracic segments and wing pads 

 light yellow, wing pads projecting 

 out from the body at a very acute 

 angle. Legs pale, tarsal apices dusky. 

 Body beset with long capitate spines 

 in four rows. Cornicles on segment 6 

 of the abdomen, hardly perceptible, 

 broader than long. Cauda blunt, 

 conical, and short. Cornicles and cauda concolorous with the abdomen. Beak 

 pale, reaching to the middle coxae. Measurements: Length of body (average), 1.87 

 mm.; width of body (average), 0.71 mm.; antenna, joint I, 0.058 mm.; joint II, 0.050 

 mm.; joint III, 0.287 mm.; joint IV, 0.207 mm.; joint V, 0.201 mm.; joint VI, 0.128 

 mm.; filament, 0.136 mm. 



This pupa is distinguishable from that of Chromaphis by the pres- 

 ence of the dorsal rows of spines and by the absence of the black 

 femoral spots. The penultimate instar occupies on the average four 

 or five days. At its termination the final molt occurs, and after this 

 the insect has acquired its full development. 



Fig. 9. 



Monellia caryx: Pupa of winged viviparous 

 female. (Original.) 



