13 
pupa skin from which the end of another Pimpla cocoon slightly extruded. 
In all such cases the removal of the perfect pupa skin showed its con- 
tents to be a very closely packed mass of Pimpla cocoons. In one case 
of this kind the pupa skin was found to contain six large female cocoous 
of the Pimpla and one larva which had died while engaged in spinning 
and had only succeeded in spinning a thin web, while attached to the 
outside of the pupa skin were four large perfect Pimpla cocoons. 
With this species, as with so many other parasitic Hymenoptera, and 
indeed as with so many other insects in general, there was a marked 
priority in the issuing of the males. The proportions of the sexes were 
carefully noted among those issuing in March. 1890, with the following 
rather striking results: 
March 3 2 A March 17 
2 A 
1 A 
2 A 
6 A 
11 $ 
9 A 
18 A 
7 3 
1 5 
8 A 
1 9 
1 A 
18. 
19 
20. 
21 
23 
24 
26 
1 A 
x 9 
A 
3 9 
9 A 
14 9 
1 A 
20 9 
1 A 
5 9 
2 A 
99 
1 A 
1 9 
8 A 
6 9 
1 i 
1 9 
The pair issuing March U7 were placed in the same vial and watched. 
They at once copulated and repeated the act seventeen times during 
the first ten minutes and six times during the next ten minutes. They 
then rested for a time. During the next hour, however, they copulated 
live times and during the succeeding two hours six times. On March 
28 both were still alive, but on the 30th both were dead. 
It is worthy of remark that these spring individuals from overwinter- 
ing cocoons are smaller in size than those which issued the previous 
September. 
It happened on several occasions that the adult Pimpla was observed 
to oviposit in tussock-moth caterpillars which were already infested 
with Tachinid larvae. Several such caterpillars were isolated for obser- 
vation, and in every case but one there was no development to maturity 
of either the dipterous or the hymenopterous parasite. In one case, 
however, an adult of the Tachinid Euplwrocera chiripennis issued from 
such a caterpillar. The probabilities are that its larva was already 
well grown when its host was stung by the Pimpla and that the larvae 
of the latter failed to find sufficient nourishment for development. 
Such instances would seem to show that the maternal instinct is not 
so prescient as has been supposed, and that all the preliminary investi- 
gation of the host insect by the mother parasite and all the apparently 
anxious soundings and tappings Avith her antennae, while appearing to 
satisfy her that everything is all right, do not always result in the 
depositing of the eggs under just the proper conditions. It is alto- 
gether likely that other parasitic Hymenoptera occasionally, and per- 
haps frequently, make similar mistakes, and that many parasites suffer 
