212 
IOWA ACADEMY OF SCIENCE 
To take a concrete example of this kind 50 Apanteles cocoons collected 
October 10 gave the following parasites in the spring of 1911. From April 1 
to 10, 11 Hypopteromalus emerged; from April 22 to 29, 3 Mesochorus emerged; 
from May 3 to 16, 25 Apanteles emerged. 
While the several parasites emerged in separate groups, there was a difference 
in the order in which they emerged. In the fall Apanteles preceded Hypop- 
teromalus in emerging, but in the spring this order was reversed. With Meso- 
chorus, however, the order in relation to Hypopteromalus varied; sometimes 
emerging before that species, again after it, but always maintaining a separate 
time in emerging. From Apanteles cocoons collected October 5 and 12, 14 Meso- 
chorus emerged, all preceding Hypopteromalus, while from cocoons collected 
October 10 and 18, 13 Mesochorus emerged, following the emergence of Hypop- 
teromalus. No difference, then, was noted in the precedence of one species 
over the other that could be correlated with the time of collection of the 
cocoons. 
It may be noticed that in the lot of cocoons collected September 30 only a 
very few Hypopteromalus were reared, and no Mesochorus. The reason for this 
is not apparent, but it is possible that these cocoons had not been formed 
long enough to have become very much parasitized. The age of the cocoons 
at the time of collection would determine to a great extent the degree of 
parasitism by Mesochorus and Hypopteromalus. 
In the case of Hypopteromalus viridescens the males preceded the females 
in emerging. Out of 730 of this species where the sex was distinguished there 
were only five cases where the males issued after the females had begun to 
come out. 
The females of Hypopteromalus were much more abundant than the males, 
there being nearly twice as many. Out of 730 Hypopteromalus where the sex 
was noted, 475, or 65% were females, while only 255, or 34.9% were males. 
The sexes are easy to distinguish, the males being light green in color, 
while the females are blue green, much darker than the males. In fact 
the two sexes might easily be taken for two different species. The sharp 
pointed abdomen of the female distinguishes it from the blunt ending abdomen 
of the male. 
In leaving the cocoon Apanteles always cuts out a tiny cap from one end 
of the cocoon, in order to make a way out. This cap then fits down nicely 
over the exit hole, sometimes closing over after the adult has emerged, but 
usually remaining open. The secondary parasites, however, both make a jagged 
hole in the Apanteles cocoon, usually at the side of the end, through which 
they emerge. So by examining the exit hole in the cocoon one can easily 
determine whether Apanteles or an enemy of the Apanteles has emerged. 
The excessive abundance of the primary parasite, Apanteles congregatus, at 
Ames in the fall of 1910 had its effect on the tomato-worms. During 1911, 
both on potato and tomato plants at Ames, not a single larVa of this species 
could be found, although a search was made time and again. A few larvae 
of the northern species, Phlegethontius quinquemaculata, were found, but even 
these were not at all common. The tomato-worm, however, was not at all in 
evidence at Ames in 1911, and its absence is no doubt due to the great abundance 
of the parasite, Apanteles congregatus, in 1910. 
