Feb. 91, 19x6 
Green Apple Aphis 
967 
plished by means of a bladelike egg burster, which extends from the 
region of the trophic tubercle over the vertex and backward on the 
crown as far as the posterior margin of the eyes (PI. LXXIII). This egg 
burster is often armed with one or two toothlike projections on its cut¬ 
ting edge. After the shell has been ruptured, the young, still within 
the membrane, protrudes for almost its entire length before the mem¬ 
brane ruptures. It is not uncommon to find insects which have reached 
this stage and died. They stand upward almost out of the shell, but 
still within the membrane. After the membrane has become ruptured 
and the insect has emerged, the former position of the egg burster is 
indicated by a suture-like marking extending over the vertex and crown 
and separating the two halves of the dark-colored cap met with in the 
stem mother of this species. 
PLAN OF DESCRIPTIONS 
It has been found by the study of the different instars that the easiest 
method for separating them is by the character of the antennae. By 
measurements of these organs it is possible to determine immediately the 
instar of the form examined. In describing the different stages, there¬ 
fore, in the earlier instars, measurements of the antennae only are given, 
and these are followed by a complete description of the adult form. In 
the third instar of the summer forms those insects destined to become 
pupae can be distinguished from those destined to become wingless only 
by the presence of the beginning of the wing pads. The measurements 
for both are the same. For the first two instars, therefore, only one 
description is given. The pupae of the intermediate and that of the 
winged form are the same in every respect, and, therefore, only one 
description is given for these forms. 
It is often important to know, immediately on their hatching from 
the egg, to what species apple aphides belong. We give here, therefore, 
measurements of the antennae of the first-stage stem mothers of the more 
common apple-infesting species which are likely to be confused—viz, 
pomi, the green apple aphis, avenae (PI. LXXIV, fig. 15, 18), the apple- 
grain aphis, and malifoliae (PI. LXXIV, fig. 17), the rosy apple aphis. 
The adult stem mothers of these species could hardly be confused, on 
account of their different color characters, but the newly hatched insects 
are most easily and definitely separated by an examination of the 
antennae. 
The relative lengths of the proximal and distal portions of the fourth 
antennal segment in the different species are given in Table I, and an 
examination of these figures will enable one to separate the species 
easily. 
