64 BULLETIN 903, U. S. DEPARTMENT OF AGRICULTURE. 
In the cellar and incubator during 1913 the phylloxeras developed, 
on the average, more slowly than in the cellar during 1911 and 1912. 
notwithstanding higher temperatures in 1913. This resulted from the 
fact that the food supply was much more succulent in 1911 and 1912. 
Likewise the phylloxeras deyeloped much more rapidly in the cages 
in 1913-1915 than in the cellar and incubator combined in 1913, 
when the temperatures differed slightly (the difference in favor of 
the cages being about 1° daily). This also was due to the superior 
food of the liying yines. In comparing the phylloxera development 
in the cellar in 1911-12 with that in the cages in 1913-1915, it would 
appear that both temperature and food influenced the more rapid 
development observed in the cages. For 1911 alone the average grow- 
ing period was 29.37 days. This growth took place on succulent roots, 
to all appearances as succulent as the living roots upon which were 
reared the 1913-1915 phylloxeras, which averaged about a 25-day 
period, under a temperature averaging 4J° in excess of that obtain- 
ing in the cellar in 1911. It would be natural to ascribe the faster 
growth in the cages to the higher temperatures, but in view of the 
discrepancies noted above in connection with the 1913 cellar and 
incubator observations, the writers are inclined to believe that the 
living roots afforded better nourishment to the phylloxeras than did 
the severed roots of 1911 and that the higher temperatures of 1913 
had less influence than might appear in bringing about such a dif- 
ference in the growing periods. 
Excepting for a few isolated instances, the phylloxeras on living 
roots developed more rapidly on nodosities and tuberosities than on 
the normal surface of the root. On nodosities development was the 
most rapid, noticeably more rapid than on tuberosities, and the more 
fleshy the swelling the more rapid was the aphid's growth, 
DESCRIPTION OF STAGES. 
The egg. — TYlien first laid, the radicicole egg (Pis. VIII. g: IX, 
L\ 1) is lemon yellow, about twice as long as wide, oval, both ends 
rather bluntly rounded, the micropylar end a little more abruptly 
so. Thirty-six eggs laid by newly matured adults August 30 and 
September 6, 1911, averaged 0.348 mm. in length and 0.173 mm. in 
width, with maxima, respectively, of 0.36 and 0.18 mm., and minima, 
respectively, of 0.34 and 0.17 mm. Of 25 eggs laid by overwintered 
radicicoles near the end of their laying period, the maximum length 
was 0.32 mm., the maximum width 0.18 mm., the minimum length 0.20 
mm., and the minimum width 0.12 mm., the average length 0.26 mm., 
and the average width 0.14 mm. Thus it appears that the size of the 
eggs laid by individuals decreases toward the end of their egg-laying 
