A STUDY IN HYPERPARASITISM 29 
The period from egg to adult requires only 13 to 18 days and there 
are several generations annually. Like the other pteromalids dis- 
cussed above, this species is ectoparasitic within the host cocoon 
and hibernates as mature larvae, the adults of the overwintering 
generation appearing in May. 
ELASMIDAE 
ELASMUS ATRATUS HOWARD 
This species has been one of the rarest among the hyperparasites 
of Apanteles melanoscelus, having been obtained from only a very 
few cocoons. It has been recorded by Howard (15) as an abundant 
parasite of A. hyphantriae, and (16) as an occasional parasite of A. 
delicatus Howard, the tussock moth parasite. In the former paper 
other species of Elasmus are mentioned as sometimes primary on Lepi- 
doptera, such as Tischeria and Aspidisca; and it is probable that 
atratus will also attack hosts of that type. A. melanoscelus cocoons 
appear to be too thick and tough to be readily pierced by the oviposi- 
tor of this species. Females of /. atratus were very often observed in 
the laboratory attempting oviposition in these cocoons, but very 
rarely were they successful. 
In hibernating as a pupa within the host cocoon, Elasmus differs 
from most hyperparasites and agrees with the two species of 
Dimmockia mentioned below. 
EULOPHIDAE 
DIMMOCKIA INCONGRUUS (ASHMEAD) 
(Fig. 9) 
Reared regularly from nearly all collections of Apanteles melan- 
oscelus cocoons of both generations, Dimmockia incongruus is often 
obtained from this host in enormous numbers; it has also been reared 
from various Braconidae and Ichneumonidae, and more rarely from 
Tachinidae. A large number of adults may be obtained from a 
relatively small number of cocoons, for this species is gregarious in 
the larval stage, sometimes as many as a dozen, or even more, indi- 
viduals maturing within a single host cocoon. Counts covering 
several hundred parasitized cocoons gave an average of six adults 
per cocoon. A gregarious parasite of this character is able to maintain 
itself in considerable abundance on a relatively small number of hosts. 
Observations over several years have shown that D. incongruus 
passes through not more than two generations annually, and that 
often there is but one. This is in rather marked contrast with the 
habit of Dibrachys boucheanus, the other very common gregarious 
parasite of Apanteles melanoscelus. Progeny of the same individual 
Sometimes issue in part the same season and in part the following 
year, the same irregularity in the number of generations existing 
which has been observed with most other hyperparasites. When 
there are two generations the first requires only 11 to 23 days for 
development from egg to adult, with an average of 16 days, whereas 
the second covers 10 months or more. The female usually deposits 
several eges at one insertion of the ovipositor; this was determined 
by dissecting cocoons which had been closely observed and had been 
allowed to be attacked only once. The eggs, which are placed any- 
