CO 
A STUDY IN HYPERPARASITISM 7 
made in the cocoons by the ovipositor. This feeding has sometimes 
been so extensive, in the case of particular individuals, that practi- 
cally the entire fluid content of the host parasite has been consumed. 
In these instances the young hyperparasitic larvae, on hatching from 
the eggs that had been unwisely deposited in the cocoons, found 
themselves without a supply of food upon which to develop, and 
necessarily died of starvation. Not infrequently the hyperparasite, 
after having punctured a cocoon several times and fed at the openings, 
was observed to leave without depositing an egg. As the primary 
parasites thus fed upon by the adult hyperparasites were always 
unable to complete their transformations, this habit of the secondaries 
must be regarded as increasing their power of destruction. To what 
extent adult hyperparasites depend upon this manner of feeding for 
obtaining their nourishment it is impossible to say. A large part of 
the Apanteles melanoscelus cocoons collected in the field and held at 
the laboratory for the emergence of parasites yielded neither primaries 
nor secondaries. With a few of the collections the proportion of such 
cocoons was more than 80 per cent of the number collected. In view 
of the feeding habit just discussed it appears likely that some of 
these Apanteles had been so heavily fed upon by adult secondaries 
that they not only had been killed, but no longer contained sufficient 
food to nourish hyperparasitic larvae to maturity. However, the 
failure of the cocoons of primary parasites to produce either primary 
or secondary adults can not be attributed to this cause alone; for the 
vigorous competition between hyperparasites for the same hosts very 
often results in the failure of any of the competing individuals to 
mature; and this competition is usually very extensive. 
Doubtless adult hyperparasites are also nourished by other sub- 
stances than the fluid content of the larvae of their host species. 
The readiness with which they feed upon a honey or sugar solution 
in the laboratory leads to the assumption that honeydew and other 
sweet juices, including sap and nectar, must form a considerable 
part of their diet. Certainly this must be the case when hosts are 
scarce. 
PARTHENOGENESIS 
Parthenogenesis, or reproduction without fertilization, has been 
so often noted with the parasitic Hymenoptera that it may be regarded 
as of general occurrence in these groups. All the hyperparasitic 
species attacking Apanteles melanoscelus were found capable of 
reproducing without previous fertilization, as would be expected. 
But of particular interest in this connection was the observation 
that different species of a given genus may differ with regard to the 
sex of the progeny resulting from parthenogenetic reproduction. 
One of the two common species of Hemiteles reared from Apanteles 
was found to be arrhenotokous, whereas the other is always thelyo- 
tokous. The two species of Pleurotropis and those of Anastatus 
obtained from the Apanteles cocoons differ in the same way, one 
species in each genus always producing males, the other females. 
Males of the thelyotokous species have not been encountered, or 
at least have not been recognized. It was rather surprising to find 
as many as four of the species handled in these studies producing 
females in parthenogenesis, for the parasitic Hymenoptera are 
considered to be very generally arrhenotokous. 
