A STUDY IN HYPERPARASITISM 33 
decided advantage, for they are able to maintain themselves in large 
numbers irrespective of the periodic fluctuations of particular pri- 
maries. The difficulty of establishing primary parasites in new 
localities is greatly increased because of this, for the secondaries 
native to the country in which it is desired to establish the primaries 
will attack the latter as readily as they do native species. 
The larvae of hyperparasites, for the most part, feed exter- 
nally upon their hosts, which are usually protected within cocoons 
or puparia. There are some interesting exceptions, however, in- 
eluding such widely different forms as Mesochorus, Charips, and 
Pleurotropis, representing respectively the Ichneumonoidea, the 
Cynipoidea, and the Chalcidoidea. 
The habit of adult secondaries of feeding at the puncture holes 
made by the ovipositor is very general and is doubtless responsible 
for much destruction of primary parasites. Eggs are not always 
deposited, indicating that insertion of the ovipositor is often for the 
sole purpose of making an opening at which the secondary can feed. 
Probably without exception hyperparasites can reproduce without 
fertilization, and in the case of nearly all species males are the result 
of such reproduction. With a relatively small number of forms, 
however, females are produced in parthenogenesis. Four species, 
Hemateles tenellus Say, Anastatus pearsall, Ashm., Eupelminus sal- 
tator (Lindm.), and Pleurotropis nawai (Ashm.) among the parasites 
attacking Apanteles melanoscelus were found to be thelyotokous. 
About 35 species of hyperparasites have been reared from cocoons 
of A. melanoscelus. Fourteen of these are responsible for more than 
90 per cent of the total parasitism, and four species, Hurytoma 
appendigaster (Swed.), Dibrachys boucheanus (Ratz.), Hemiteles tenel- 
lus (Say), and Dimmockia incongruus (Ashm.), destroy many more 
Apanteles than all the other species combined. 
Extensive collections of Apanteles melanoscelus cocoons, which have 
been held for the issuance of primaries and secondaries, indicate that 
from 25 to 30 per cent of the first-generation cocoons produce adult 
Apanteles, while less than 1 per cent of the second-generation cocoons, 
which are formed in July and must carry the species over the winter, 
produce adults of the primary the following spring. Fifty per cent 
or more of these cocoons yield neither primaries nor secondaries, as a 
result of the extensive feeding of the adult hyperparasites and the 
very strenuous competition between the secondaries for the same 
individual hosts. 
Individuals of several species of secondaries were carried through 
their entire development from egg to adult in glass cells to determine 
the number of larval stages, the rapidity of larval growth, and the 
length of the periods spent in the egg, as larva, and as pupa. In 
the case of all the species observed, which included the ichneumonids 
Hemiteles tenellus and Gelis bucculatricis Ashm.: ;aeurytomid, Hurytoma 
appendigaster; two eupelmids, Hupelmus spongipartus Foerst., and 
-Anastatus pearsalli; apteromalid, Dibrachys boucheanus; and aeulophid, 
Dimmockia wncongruus, there were five larval stages. The feeding 
period is nearly always very short, rarely more than 36 hours being 
spent in any of the larval stages except the last; in the last stage, 
too, feeding ends after from 24 to 48 hours, but several days are usually 
spent as a resting larva before pupation. 
All the hyperparasites obtained from Apanteles melanoscelus, with 
the exception of the two species of Pleurotropis, were found to be 
