52 POMONA JOURNAL OF ENTOMOLOGY 



by digitules, these digitules also cover the entire body in great numbers, as is 

 shown in the cut, but disappear with age, as there are none on the adults. 

 Antennae (Figure 36 D) five-jointed and short, being 0.58 mm. long. The com- 

 parative lengths of the various articles are: I .05 mm., II .05 mm.. Ill 1.18 mm., 

 IV 0.2 mm., V 0.1 mm. The margins of the abdomen are deeply serrulated 

 between the many digitules. Rostrum very short, scarcely reaching beyond the 

 pro-thorax. Legs as in the adult, only the hind tibia are marked, but in many 

 cases the middle tibia, and in some cases, all the tibia are marked at the distal 

 end with a conspicuous black blotch. 



Of all the Southern California Aphids this form, commonly known as the 

 Walnut Aphid, is of the greatest economic importance because of the damage it 

 does to the Walnut trees. Introduced from Europe on nursery stock, it is 

 attacking the walnut, Jitglans regiae, so vigorously as to threaten the out-put 

 greatly. Its appearance is so sudden and it often occurs in such countless num- 

 bers that the damage is done before the orchardist is aware of its presence. Last 

 year it threatened to ruin the entire crop on the Limoneira Ranch. It appears 

 to infest walnut trees throughout Southern California, settling on the under side 

 of the leaves, in numbers which at times entirely hide the whole surface. 



