- 11 - 
Table 2. — Approximate duration of the incubation period of eggs of 
H vpera bru n n eipennis under insectary conditions, Yuma, 
Ariz., January to May 1940 
Date deposited 
In cubation period (day s) 
Range Average 
Dec. 
30 - 
Jan. 
2 
Jan. 
6 - 
Jan. 
8 
Jan. 
8 - 
Jan. 
10 
Jan. 
12 - 
Jan. 
14 
Jan. 
20 - 
Jan. 
22 
Jan. 
26 - 
Jan. 
29 
Feb. 
2 - 
Feb. 
5 
Feb. 
5 - 
Feb. 
7 
Feb. 
7 - 
Feb. 
9 
Feb. 
10 - 
Feb. 
12 
Feb. 
12 - 
Feb. 
14 
Feb. 
16 - 
Feb. 
17 
Feb. 
19 - 
Feb. 
21 
Feb. 
24 - 
Feb. 
26 
Feb. 
26 - 
Feb. 
28 
Mar. 
2 - 
Mar. 
4 
Mar. 
6 - 
Mar. 
8 
Mar. 
8 - 
Do 
Do 
Mar. 
11 
Mar. 
15 - 
Do 
Do 
Mar. 
18 
Apr. 
10 - 
Apr. 
12 
21 - 24 
21 - 23 
20 - 21 
22 
18 - 19 
14 - 19 
19 - 22 
17 - 21 
17 - 21 
16 - 17 
15 - 21 
13 - 16 
11 - 15 
10 - 14 
11 - 13 
11 - 15 
11 - 13 
9-12 
9-12 
9-12 
8-9 
8-9 
8-9 
4-7 
21.2 
21.5 
20.1 
22.0 
18.2 
15.8 
19.4 
18.2 
18.3 
16.2 
15.9 
14.1 
11.9 
11.8 
11.5 
11.7 
11.4 
10.5 
10.0 
10.3 
8.8 
8.8 
8.9 
5.1 
larval instars . Larvae of each stage vary greatly in body size and there is 
an overlapping between successive stages which renders classification on 
this basis uncertain. Results of head measurements of 100 specimens of each 
instar are shown in table 3. 
Tab.le 3 .—Measurement of larval head sizes to determine number of 
instars, of Hypera brun neipennis , Yuma, Ariz. , 1940 
Number measured 
Larval 
instar 
Width of head caps ul es (mm.) 
Range Average 
100 
100 
100 
100 
First 
Second 
Third 
Fourth 
0.195 - .210 
.260 - .300 
.395 - .445 
.565 - .650 
0.203 
.285 
.418 
607 
