12 
BULLETIN 436, U. S. DEPARTMENT OF AGRICULTURE. 
was ascertained by taking larvae that had already constructed their 
pupal cells, placing them in a vial, and alio whig them to go through 
these various changes in plain sight. 
Table IV. — Duration of pre pupal and pupal stagesofihe desert corn flea-beetle (Chaetoc- 
nema ectypa) at Tempe, Ariz.. 1915. 
Pupa Xo. 
Date 
prepupa 
formed 
-r, Length 
Date ! Le ^ th 
aeu 1 stage. 
i 
Aver- 
age 
mean 
tem- 
pera- 
ture. 
1 
2 
Z.W ..... 
4 
5 
6 
S 
9 
Apr. 30 
...do 
Mav S 
May lo 
...do 
...do 
Apr. 27 
...do 
Days. 
Mav 6 6 
...do 6 
Mav 10 2 
Mav 12 2 
...do 2 
...do 2 
Apr. 29 2 
Mav 5 S 
Mav 7 
...do 
Mav S 
...do 
...do i 
Mav 10 
MayKHo) 
Mav 11 > 
...do : 
Julv 17 ! 2 
...do 2 
pso n 
Days. 
Mav 13 '7 
...do ! 7 
Mav 14 4 
May 17 5 
...do 5 
...do 5 
Mav 11 , 12 
May 13 ] 8 
°F. 
70 
70 
76 
75 
75 
75 
63 
70 
70 
70 
73 
73 
73 
76 
75 
75 
S6 
S6 
10 
11 
...do 
Mav 14 
...do 
...do 
...do 
Mayl5(5) 
Mav 17 
...do 
Julv 20 
...do 
6 
6 
6 
6 
4 
5 
6 
6 
3 
3^ 
12 
13 
14 
15 
16 
17 
18 
19 
Julv 15 
...do 
sje of 23 pu 
The duration of the pupal stage, which was determined in the same 
way, was found to vary from 3 to 12 days, with an average of of days 
(Table IV). In a dry soil the larvae pupate at as great a depth as 4 
inches below the surface, while in an extremely moist soil the pupal 
cell is often formed within one-fourth to one-half inch of the top of 
the ground, and in one rare instance it was found at the surface of the 
ground just beneath some decaying vegetable matter. It can thus 
be readily understood that a pupa near the surface of the ground 
would receive more heat from the sun's rays, and consequently would 
develop more rapidly than one at a greater depth. This fact doubt- 
less explains some of the variations in the combined lengths of the 
egg, larval, and pupal stages hi some cages, the records of which ap- 
pear in Table I. For instance, hi cage T-136 the combined lengths 
of stages are shown to vary from 43 to 63 days, and in cage T-117, with 
a mean temperature 5 degrees lower, adults were secured in 34 days It 
is obvious that this presents a vulnerable point for attack in the life 
of this pest, for if corn is well irrigated the pupae will be formed near 
the surface of the ground, and then if each irrigation is followed by a 
careful, close but shallow cultivation, a goodly percentage of the 
pupae are exposed to the sun and the drying effects of the air, and 
hence killed. 
