292 
Journal o f Agricultural Research 
Vol. XXIX, No. 6 
Table I. — Life-history data on Polyscelis modestus a 
Host 
pupa¬ 
rium 
No. 
Date of 
oviposition 
Date of meconial 
discharge 
Date of pupation 
Length 
of 
larval 
stage 
Length 
of pre¬ 
pupal 
stage 
Date of 
emergence 
Length 
of 
pupal 
stage 
Period 
from 
egg to 
adult 
Days 
Hours 
Days 
Days 
14 
July 18_ 
July 26, 11.45 a. m. 
July 27, 2 p. m_ 
b 7 
26M 
Aug. l.__ 
5 
14 
15 
18_ 
July 27, 2 p. m_ 
7 
2___ 
6 
15 
27 
19- 
July 26,3.30 p.m., 
July 27, 2 p. m_ 
6 
22J4 
2_ 
6 
14 
at dissection. 
28 
19_ 
July 26, 3.30 p.m., 
July 27, 2 p. m_ 
6 
22M 
2_ 
6 
14 
at dissection. 
29 
19--_. 
July 26, 3.30 p. m., 
July 27, 2 p. m_ 
6 
22^ 
2_ 
6 
14 
at dissection. 
42 
22_ 
July 31, 2.30 p. m__ 
7 
43 
22_ 
July 31, 2.30 p. m 
7 
7. _ 
7 
16 
47 
22.... 
July 27, 2.30 p. m., 
July 28, 9.30 a. m.. 
4 
19 
2_ 
5 
11 
at dissection. 
54 
22.... 
July 27, 2.30 p.m., 
July 28, 9.30 a. m._ 
4 
19 
2_ 
5 
11 
at dissection. 
79 
24_ 
July 31, 2.30 p. m . 
5 
6_ 
6 
la 
80 
24_ 
July 3lj 2.30 p. m_. 
5 
6. _ 
6 
la 
81 
24.... 
July 31, 3 p. m., 
Aug. 1, 9.30 a*. m.._ 
6 
18 Yt 
7... 
6 
14 
at dissection. 
82 
24.... 
Aug. 1, 9.30 a. m.__ 
6 
83 
24.... 
Aug. 1, 9.30 a. m... 
Aug. 2, 9.30 a. m... 
7 
24 
Aug. 8... 
6 
15 
84 
24_ 
July 31, at dissec- 
5 
tion. ’ 
93 
25.... 
Aug. 1, 9.30 a. m... 
Aug. 2, 9.30 a. m... 
6 
24 
Aug. 8— 
6 
14 
94 
25.... 
Aug. 1, 9.30 a. m... 
Aug. 2, 9.30 a. m... 
6 
24 
8— 
6 
14 
95 
25.... 
Aug. 1, 9.30 a. m... 
Aug. 2, 9.30 a. m... 
6 
24 
8— 
6 
14 
97 
25.... 
Aug. 1, 9.30 a. m.__ 
Aug. 2, 9.30 a. m... 
6 
24 
8.__ 
6 
14 
101 
26.... 
Aug. 2, 9 a. m. 
Aug. 3, 10.30 a. m. 
6 
25^ 
9... 
6 
14 
109 
26.... 
Aug. 4, 2 p. m. 
Aug. 6, 10 a. m_ 
9 
44 
13„_ 
7 
18 
110 
26 
Aug. 2,9.30 a. m 
9. _ 
14 
111 
27.... 
Aug. 4, 9 a. m. 
Aug. 5, 12 m. 
7 
27 
12._ . 
7 
16 
116 
27.... 
Aug. 3, 6 p. m... _ 
Aug. 4, 2 p. m. 
6 
20 
11 — 
7 
15 
123 
27.... 
Aug. 4, 9 a. m. 
Aug. 5,12 m.. 
7 
27 
13— 
8 
17 
124 
27.... 
Aug. 3, 10.30 a. m._ 
Aug. 4, 9 a. m. 
6 
22M 
11— 
7 
15 
125 
27.... 
Aug. 3, 6 p. m. 
Aug. 4, 9 a. m- 
6 
15 
11 — 
7 
15 
132 
28.... 
Aug. 3, 6 p. m. 
Aug. 4, 9 a. m. 
5 
15 
11— 
7 
14 
137 
28.... 
Aug. 4,9 a. m. 
Aug. 4, 2 p. m_ 
5 
5 
12— 
8 
15 
138 
28-.. 
Aug. 6, 10 a. m_ 
Aug. 10, 10 a. m... 
11 
96 
15-_ 
5 
18 
149 
30—. 
Aug. 6, 10 a. m_ 
Aug. 6, 5.30 p. m_. 
5 
7 Vi 
13— 
7 
14 
° The data in the foregoing table may be summarized as follows: Average length of larval period for 30 
larvae, 6.17 days; variation in length of larval period, 4 to 11 days; average for 23 prepupae, 24.99 hours; 
variation of prepupal period, 5 to 96 hours; average for 27 pupae. 6.3 days; variation for pupal period, 5 
to 8 days; average for 28 adults, 14.46 days; variation period from egg to adult, 11 to 18 days. 
b Larval stage obtained by subtracting an incubation period of two days from time elapsing between 
date of oviposition and date of pupation. 
PREPUPA 
When the larva becomes full grown 
and is ready to pupate it voids the 
meconium and reverses itself within 
the puparium. Turning its head in 
the opposite direction from the host 
remains and the meconial substance, 
it then transforms to the prepupal 
stage. In this stage a constriction 
appears between the thoracic and the 
abdominal segments. 
The length of the prepupal stage 
was from 5 to 96 hours, the average 
being about 25 hours for 23 prepupae 
(Table I). 
PUPA 
The pupa (fig. 1, e) when first 
formed is pure white. As the pupa 
ages the eyes become red and the 
mandibles brown. After this the 
whole pupa very rapidly assumes a 
light-brown color. The pupa is from 
1.5 to 1.95 mm. in length and from 
0.5 to 0.65 mm. in width. The aver¬ 
age length of 10 pupae was 1.8 mm. 
and the average width was 0.6 mm. 
The pupal stage lasts for a period of 
from 5 to 8 days. The average length 
of the pupal stage for 27 pupae was 
6.3 days (Table I). All the data on 
this stage are based on observations 
confined to pupae of the male sex. 
The total period from oviposition to 
the emergence of the adult was from 
11 to 18 days in length. The average 
for 28 adults was about 14J^ days 
(Table I). 
ADULT 
The adult female (fig. 2, a) is about 
2 mm. long. It may be readily distin¬ 
guished from the other Hessian fly para¬ 
sites by a large, faint, subcircular, 
fuscous spot in the middle of the fore- 
