THE DESEET CORN FLEA-BEETLE. 
13 
THE ADULT. 
The change from pupa to adult takes place rather quickly, but 
often a day or two passes before the adult entirely assumes the char- 
acteristic shining black. When the adults first emerge from the 
pupal state they are almost white, but after a short time gradually 
become darker, beginning with the legs, then the elytra, and finally 
the whole body is enveloped. 
The adults are very soon able to jump nimbly and it is this habit 
which has given this group their name of " flea-beetles." They are 
quite easily alarmed, leap quickly from a plant, and, falling to the 
ground, often feign death in order to escape their enemies. 
To the ordinary observer the males and females are very much 
alike, the difference being largely one of size, the male averaging 
slightly smaller than the female. A gravid female can be distin- 
guished by the size of her abdomen, but large males are often larger 
than small females, so that the distinction is not very reliable. 
ADULT DEVELOPMENT. 
After the adults emerge several days must elapse before their 
sexual development is completed. Numerous records on this point 
were made by the writer as well as by J. H. Newton, assistant in the 
bureau at Tempo, and it was found that copulation usually takes 
place from 4 to 6 days after emergence and oviposition from 4 to 5 
days thereafter. Table V shows the length of the period elapsing 
from issuance to oviposition as observed in live females. This varied 
from 7 to 14 days, the average being 9.8 days. 
Table V. — Length of life of the desert corn flea-beetle (Chaetocnema ectypa) at Tempe, 
Ariz. -1915. 
Date adult issued. 
On or before Apr. 25. 
On or before Apr. 20. 
May 7 (3) 
May 17 
Do 
July 16 
Do 
On or before Apr. 28. 
Average. 
Date ovi- 
position 
began. 
Age at 
begin- 
ning of 
ovipo- 
sition. 
Apr. 29 
Apr. 28 
May 22 
May 26 
May 29 
July 23 
July 25 
May 7 
Days. 
Adult 
died. 
June 1 
May 31 
May 27 
June 15 
..do.... 
July 31 
..do.... 
July 20 
Length 
of life. 
Days. 
38+ 
41+ 
20 
29 
29 
15 
15 
83 
33.6 
NUMBER OP EGGS DEPOSITED BY ONE FEMALE. 
The females usually lay their eggs in stages, there being from one 
to two, and sometimes three, different egg-laying stages, often extend- 
ing over half a month. As shown in Table VI, a female may deposit 
