8 DEPARTMENT BULLETIN 1267, U. S. DEPT. OF AGRICULTURE 
occurs in nature. The experience of the writers, however, both in 
the field and in experiments, indicates that an excess of moisture 
is almost as unfavorable for the eggs as a deficiency. The places 
in which the species normally occurs and in which it breeds most 
abundantly are so situated with reference to local drainage condi- 
tions that, although the ground retains a constant supply of avail- 
able moisture, it is never saturated with water for any considerable 
period of time during summer. It is doubtless these moisture re- 
quirements which underlie the marked tendency of the species to 
congregate in the lowlands bordering marshes and drainways and 
to be limited on the higher ground to local sunken areas in which 
the soil is rather slowly drained. 
INCUBATION 
Experiments on the duration of the period of incubation were 
conducted at Charlottesville. Owing to conditions attending the 
work, it was rarely possible to determine the precise time at which 
an egg had been deposited, and, for this reason, the results obtained 
are at best but approximations. On one occasion (July 26) a female 
was found in the act of depositing an egg. On August 9 this egg 
hatched, giving an incubation period of 14 days. 
There may be considerable variation in the time required for in- 
cubation. This may be accounted for by variations of temperatures, 
high temperatures accelerating and low ones retarding development. 
As a rule, the period of incubation under favorable midsummer con- 
ditions varies from two to three weeks. In the fall this time is 
greatly extended, extremes of from 35 to 50 days being reached in 
October and November. All eggs which had failed to hatch by 
the middle of November were buried in their containers in the ground 
and there kept over winter. In early April they were dug up and 
examined, but in all instances the eggs were dead. 
HATCHING 
The chitinized larval jaws may be seen through the translucent 
egg membrane (PI. II, D) several days before hatching takes place. 
When hatching occurs, the egg membrane appears to collapse and. 
to split at a point close to the dorsal surface of the larva. In one 
instance the rupture of the membrane occurred in the vicinity of the ~ 
thoracic region; in another at about the level of the third abdominal 
seoment. It evidently results from the contortions of the inclosed 
larva in an effort to free itself. After the membrane has split the 
larva continues its efforts, bending and extending its body at fre- 
quent intervals until it has finally managed to extricate itself, though 
occasionally portions of the membrane may adhere to the larva for 
a considerable time after hatching. In no instance did the larve 
make any attempt to devour the egg membrane. 
The time consumed in the process of hatching was in one instance 
7 minutes, in another 35 minutes. Plate II, /, shows the newly 
hatched larva and Figure 3 shows the relative size of the head and 
body immediately after hatching. 
