THE GRAIN BUG. 11 
RELATION OF TEMPERATURE TO INCUBATION. 
In laboratory experiments and in the field it was observed that 
variations in temperature had a pronounced influence in determin- 
ing the length of the egg period. In one experiment half of a newly 
deposited egg cluster hatched in 4 days when exposed to a maxi- 
mum. daily temperature of 90° F. while the remaining half of the 
same ege cluster which was exposed to a maximum daily tempera- 
ture of 70° F. required 7 days to complete its period of incubation. 
(See Table I.) 
TABLE I.—felation of temperature to incubation and nymphal development in 
Chlorochroa sayi. 
eee a bins 
period. 
Second 
instar. instar. 
Days. Days. Days. 
7 14 
Maximumydatlyitemperaturerofi70? Wi. 2 i 5042 geese 9 
Maximum daily temperature of 90° F......-..-....------.2------ es ee 4 4 7 
Ditkerence for 20° HA of temperature...) !2252.2522 2. Geek Pele 3 | 5 7 
DETAILS OF HATCHING. 
When nearly ready to hatch, the eggs assume a darker color than 
during the earlier stages of their development. Upon dissecting one 
of these eggs it is found that the fully developed nymph is inclosed 
within a delicate transparent membrane. On the outside of this 
membrane just under the lid of the egg, and at a point opposite the 
vertex of the head of the inclosed nymph, is a black, chitinized 
T-shaped structure which functions as a shell burster. The curved 
top of the T, or shell burster, follows a curved line running from eye 
to eye of the nymph over the vertex of the head. The shank of the 
T follows the median dorsal line of the nymph posteriorly. <A short, 
stout spine occupies about one-third of the median portion of the T 
at the point where the lines intersect. This spine is directed at the 
suture between the lid and the neck of the egg at a point opposite 
its hinge. During the process of hatching the struggles of the 
nymph against the shell burster exert a strong lifting pressure on 
this spine and the lid of the egg is partially raised. At the same 
time the inclosing membrane splits just back of the shell burster 
and slips forward over the head of the nymph. As the integument 
of the nymph is very soft, the emergence is by slow periodic move- 
ments apparently exerted from within the body of the nymph. The 
first portion of the nymph to be free is the first pair of legs, followed 
by the antenne, rostrum, second pair of legs, third pair of legs, head, 
thorax, and abdomen in the order named. 
