PABASITE, APHIDIUS TESTACEIPES. 
113 
emerge as an adult after the first movements of the pupa begin, and 
when ready to issue the pupa expands and contracts the abdomen, 
moving the feet and antennae until these are freed from their gum- 
like covering. Upon studying the pupae (jig. 27) 
closely, we find that the prothorax bears two rows 
of distinct elevations or tubercles, but we have 
been unable thus far to ascribe any particular 
function to them and they disappear with the 
gum-like covering. The junior author finds that 
the adult gradually works itself about until it gets 
in a position with its back to the ventrum of the 
old aphidid shell, when it cuts a circular hole, as 
described by Mr. Kelly, and crawls out, always 
with its head pointing toward the head of the old 
aphidid. Figure 28 represents an old dead body of 
a " green bug" after the parasite has issued. 
FECUNDITY. 
Fig. 27. — Pupa of 
Aphidius testaceipes 
immediately after 
pupation. Much 
enlarged. (Origi- 
nal.) 
From the prompt manner in which Aphidius, under favorable 
weather conditions, overcomes Toxoptera it will readily be seen that 
the former must be a very prolific breeder. The 
average adult female contains from 4 to 450 
eggs. These eggs are lemon-shaped (see fig. 
19), very pale, and translucent. 
Messrs. Kelly and Urbahns conducted a 
number of experiments at Wellington, Kans., 
in 1908, to determine the number of offspring 
produced by one individual. They found that 
one Aphidius would parasitize as many as 206 
Toxoptera. In their experiments, however, 
they used only a few more than 200 Toxoptera 
to each individual. Mr. Parks, at the same 
place in 1909, conducted 16 experiments, using 
from 300 to 500 Toxoptera and he had a maxi- 
mum, in one case, of 301 aphidids parasitized 
from one individual Aphidius. His minimum 
was 3; his next highest number was 33, and 
his next was 44. Of the sixteen, 12 fell below 
100; his average was 94.6. 
Mr. Parks also conducted experiments at the 
same time as the above to ascertain what the ef- 
fects of continuous mating of one male to differ- 
ent females would have on the offspring. In 
this experiment 1 male was mated to 12 unfertilized females within a 
period of two hours, after which each female was placed in a separate 
cage with about 100 Toxoptera that had not been exposed to Aphidius. 
26675°— Bull. 110—12 8 
Fig. 28.— Dead "green bugs" 
(Toxoptera graminum), 
showing holes from which 
the matured parasites of 
A phidius testaceipes emerge. 
The top figure shows the lid 
still attached, but pushed 
back; the bottom figure 
shows the parasite emerg- 
ing. Enlarged. (From 
Webster.) 
