BULLETIN 100, U, S. DEPARTMENT OF AGRICULTURE. 



LIFE HISTORY AND TECHNICAL DESCRIPTIONS. 



The Viviparous or Asexual Forms. 



When, the young stem-mother is ready to emerge in the spring she 

 causes the shell of the winter egg to burst with a longitudinal slit on 

 the dorsal surface from the micropylar end. (See fig. 1.) Egress is 

 performed head first, and antennae and legs are requisitioned by the 

 young larva in worming its way out of the shell. While the process 

 of emerging, which occupies half an hour or more, is taking place, the 

 aphis assumes an erect position at right angles to the long axis of the 

 egg. After the exit of the young the eggshell has a large triangular 

 hole at the micropylar end. 



As soon as the buds begin to swell in early spring these stem-mothers 

 hatch and continue hatching until the leaves have fully opened out, at 

 which time all will have issued from the egg. The earliest plant-lice 

 to emerge may be seen wandering over the bare twigs and buds, 

 apparently feeding a little upon the scales protecting the unopened 

 buds, but not showing much growth until the buds 

 have opened and can afford nourishment. 



Undoubtedly many of the aphides that hatch 

 early die of ill nourishment, and some of these do 

 not attain their full development for six or seven 

 weeks, while those hatching later and finding 

 ¥iG.i.—chromaphusjugiandi- tender food in abundance become full grown at 



I'otif^ched^^went'y tne eild of five weeks - Certain it is that on a 

 times natural size. (Orfgi- particular tree the stem-mothers all became 

 winged almost simultaneously. On trees which 

 leaf early the stem-mothers will begin emerging {from the egg as 

 early as February 15, but on the Franquette and such late varie- 

 ties no aphides will be found until in April. Immediately after 

 hatching the lice seek the buds-or young leaves. In the former case 

 the aphides crawl in between the scales, but on the leaves they 

 appear on the lower or exposed side, notwithstanding the fact that 

 much better protection is afforded by the upper, as yet unfolded, sur- 

 face which at that time is almost entirely hidden from view. Possibly 

 the sticky character of the upper surface of the leaves repels them. 

 Table I indicates the life cycle of four stem-mothers which hatched 

 after the buds had opened. 



Table I. — Period of development of the stem-mother of Chromaphis juglandieola, San 



Jose, Cal., 1912. 



No. of individual. 



Date of 

 hatching. 



Date of Period from 



acquiring hatching to 



wings. maturity. 



1 



Mar. 24 

 24 

 24 

 24 



Apr. 28 

 28 

 28 

 29 



Days. 

 35 

 35 

 35 

 36 



2 



3 



4 



Average period . 



35.25 







