580 
Journal of Agricultural Research 
Vol. XXIX, No. 12 
months at Quincy, Fla., incubation re¬ 
quires about 11 days, whereas in sum¬ 
mer the eggs usually hatch in about 5 
days. The period may, however, vary 
considerably within the same range of 
temperatures. Eggs deposited the same 
day sometimes vary as much as 4 days 
in the date of hatching. 
Table I. —Summarized deposition rec¬ 
ords of the tobacco flea-beetle obtained 
June 1 and 2, 1923, at Quincy, Fla., 
showing time of day at which eggs are 
deposited 
Time interval 
Eggs de¬ 
posited 
Percent¬ 
age 
5 a. m. to 7 a. m_ 
130 
9.0 
7 a. m. to 12 m. 
211 
14.5 
12 m. to 6.30 p. m. 
366 
25.2 
6.30 p. m. to 8 p. m_ 
208 
14.3 
8 p. in. to 10.30" p. m_ 
10.30 p. m. to 5 a. m.. 
244 
294 
16.8 
20.2 
Total_ 
1, 453 
100.0 
other hand, gave as high a per cent 
hatch as in the case of soils of medium 
moisture content. 
The greatest difficulty in life-history 
studies was encountered in the larval 
stage, owing primarily to the fact that 
the moisture requirements for this stage 
are so exacting. A certain amount of 
soil moisture is absolutely essential for 
larval development, but excessive mois¬ 
ture may prove to be very detrimental. 
On the other hand, the larvae seem to 
be able to develop successfully under a 
considerable range of temperature. 
When maturity is reached the larva 
forms a small ovoid-shaped cell about 
an inch below the soil surface, and be¬ 
gins to shorten preparatory to pupa¬ 
tion. 
THE LARVA 
Description of larva emerging 
from egg. —An egg under observation 
beneath the binocular microscope began 
hatching at 12.41 p. m. The larger 
end of the egg burst open as though 
This effect of temperature upon the 
incubation of the tobacco flea-beetle 
egg is very marked. In one case, eggs 
deposited on February 12 required 26 
to 27 days for hatching, whereas several 
records giving an incubation period as 
short as 3 days have been obtained in 
midsummer. The relationship be¬ 
tween mean temperature and the 
length of the egg period is shown in 
Figure 7. 
Influence of moisture on in¬ 
cubation. —The eggs of E. parvula re¬ 
quire a certain amount of moisture for 
hatching, and the incubation period 
probably varies to a certain extent 
with the moisture conditions. Eggs 
placed by the beetles upon air-dry soil 
all failed to hatch, and eggs deposited 
on only slightly moistened soil gave a 
comparatively low hatch. Eggs de¬ 
posited on water-saturated soil, on the 
the larva had gnawed through from 
the inside. The head shield of the 
larva could be plainly seen. The 
head moved rapidly in a rotary manner, 
enlarging the opening, and was soon 
thrust out of the shell. After the head 
was free, movement ceased, except for 
a slow rhythmic movement of the body 
which could be plainly seen through the 
shell, and the larva rested for nearly 
a minute. Then the movement of the 
body quickened, the head moved 
rapidly from side to side, and in the 
course of about two minutes of un¬ 
ceasing exertion all of the prolegs were 
liberated. As soon as each proleg was 
freed it was brought into play. The 
larva twisted and pulled almost con¬ 
tinuously, pausing for a second now 
and then, only to begin again with 
renewed efforts. At the end of exactly 
eight and one-half minutes from the 
