Dec. 15,1924 Tobacco Flea-Beetle in Southern Cigar- IT rapper District 579 
which touch the ground, but older 
beetles feed on all portions of the 
foliage. 
The tobacco crop is attacked by the 
overwintered generation and by two 
later generations of flea-beetles. ~ After 
the crop is harvested there may be two 
and possibly three additional genera¬ 
tions, which so overlap that it is im¬ 
possible to tell them apart. 
The winter is passed in the adult 
stage in a more or less incomplete state 
of hibernation. 
THE EGG 
How AND WHERE DEPOSITED. -The 
egg is deposited on or near the surface 
of the soil in cracks and crevices; 
usually with the point downward so 
that only the top of the larger end can 
be seen. It may be deposited, however, 
in almost any position; on end, lying on 
its side, or at an angle, depending more 
or less on the nature of the crevice in 
which it is placed. When tobacco is set 
out in the fields the eggs are usually 
laid in the moist depression about the 
base of the stalks where the plant is 
watered at setting time. Later in the 
season, when the plants are larger, most 
of the eggs seem to be deposited some 
little distance away from the stalk, 
beneath the lower leaves resting on the 
ground, where the beetles find more 
moisture and protection. 
Number of eggs deposited. —The 
number of eggs deposited by a single 
female appears to vary greatly; this 
variation doubtless is due to many 
factors. Under cage conditions, one lot 
of overwintered females confined with 
males laid an average of 164.47 eggs. ■ 
Since the average longevity of the 
females in this cage was 44.8 days, an 
average of 3.67 eggs was deposited 
daily by each female. In this experi¬ 
ment, however, the beetles were not 
collected until the middle of April, and 
since oviposition in this locality fre¬ 
quently commences at a much earlier 
date, it is probable that a number of 
eggs were deposited before the flea- 
beetles were obtained. It can, there¬ 
fore, be assumed that at least 200 eggs 
may be deposited by a female of this 
generation. 
Two similar experiments with adults 
of the spring generation, in which a 
total of 9,257 eggs was deposited, gave 
an average deposition per female of 
100.73 eggs. In both of these experi¬ 
ments the beetles used were collected 
within two or three days after emer¬ 
gence, so that these records may be 
taken as fairly indicative of the number 
of eggs deposited by the spring genera¬ 
tion. 
All records so far obtained indicate 
that the overwintered females deposit 
a much larger number of eggs than the 
females of the later generations. If 
this is correct, it is perhaps a provision 
of nature to counterbalance the heavy 
winter mortality. 
Very few deposition records of indi¬ 
vidual females have been obtained by 
the authors. In one case, however, a 
single female deposited 12 eggs within 
24 hours. Other records have been ob¬ 
tained of as high as 21 eggs deposited 
in a mass, more or less adhering together, 
all apparently having been deposited by 
one female. 
Time of day when oviposition 
occurs. —Eggs may be deposited at 
almost any hour of the day or night. 
The summarized deposition records 
shown in Table I indicate that the 
flea-beetles have no special time at 
which they deposit their eggs. In 
obtaining these records, which cover a 
period of 11 days, the deposition cage 
was placed throughout the day on 
the ground under a tobacco plant in 
the field, where a nearly normal con¬ 
dition of sunlight prevailed. During 
the night the cage was kept on the 
laboratory porch. 
Influence of soil moisture on 
deposition of eggs. —Soil moisture 
appears to have a considerable influence 
upon the deposition of eggs. Moist 
soil, when available, is always selected 
in preference to dry soil. In one case 
350 flea-beetles, confined in a lantern- 
globe cage, were given an equal choice 
of either moist or air-dry soil upon 
which to oviposit. Over a 60-day 
period only 9 eggs were deposited on 
the dry soil as against 3,146 eggs 
deposited on the moist soil. 
Where moist soil is unavailable upon 
which to oviposit the beetles deposit eggs 
very sparingly, even over long periods 
of time. Two deposition cages, each 
containing 150 flea-beetles, were started 
at the same time, the first being supplied 
with air-dry soil, the other with moist 
soil. Over a 60-day period 287 eggs 
were deposited on the dry soil as against 
5,324 eggs deposited on the moist soil. 
Influence of temperature upon 
egg deposition. —Deposition records 
of the tobacco flea-beetle indicate that 
no eggs are deposited when the daily 
mean temperature is below 50° F. 
No relationship between the number 
of eggs deposited and prevailing higher 
temperatures could be observed. 
Influence of temperature on 
LENGTH OF INCUBATION PERIOD.- 
Temperature seems to be the deciding 
factor in regulating the length of the 
incubation period. In the early spring 
