PARASITES HIBERNATING IN BROWN-TAIL WEBS. 
275 
a very little as a rule, and the least motion was sufficient to dislodge 
the egg or young larva of the parasite. 
Oviposition upon any other host was equally unsuccessful, provided 
that the host was free to move about to any extent, but whenever 
it was confined within the limits of a cocoon, and was not too large, 
it usually fell a victim to the parasite. Especially was this true of 
the hibernating larvae of hymenopterous parasites within their 
cocoons, and from these the largest and finest Pteromalus were 
reared. 
If the parasite or h\ nienopterous larva w as very small, as in the 
instance of the larva of Apanteles. it was very likely to be killed bv 
the Pteromalus in the process of oviposition and. as a common result, 
her progeny would perish also. 
Evidence to indicate that the female parasite possesses discrimi- 
native powers which enable her intelligently to select suitable hosts 
for her young is wholly lacking, and in consequence, when several 
individuals are given access to a single nest of the brown-tail moth, 
the chances are that all of them will concentrate their at lack upon 
the few caterpillars which chance to be most readily accessible, to 
the exclusion of all others. The outcome is one of the manifold 
phases of superparasitism. The larva* hatching from the superabun- 
dance of eggs are unable to reach their full development. They ma 
complete their transformations but the adults produced are small, 
weak, and in extreme instances w holly unfit for further reproduction. 
In the work of rearing the parasite for colonization purposes, no 
matter how many parent Pteromalus were used, the number of cater- 
pillars which were parasitized by them would be a small percentage 
of those in the nests exposed to their attack, and invariably when 
more than a few females were used as parents the nests had to be 
torn open, so as to expose a large number of caterpillars equally. 
Otherwise the progeny would be so small as to be practically worth- 
less for further reproduction, colonization, or anything else. This 
in itself was sufficient to render Pteromalus of very much less value 
from an economic standpoint, and the extraordinary avidity with 
which it attacked the cocoons of other hymenopterous parasites was 
anything but a point in its favor. Most especially was this true 
when the life and habits of Apanteles lacteicolor Yier. were taken into 
consideration. It soon became evident that Pteromalus w as pecul- 
iarly fitted to act as its most dangerous enemy, and since, between 
the two, Apanteles was much the more promising parasite, it was 
decided to abandon all further effort toward the introduction of 
Pteromalus, and the work of rearing was discontinued. 
Some 250,000 larvae and pupae were on hand at the time when this 
decision was reached, and these were placed in cold storage. It was 
considered probable that the species was already introduced, if it 
