26 Psyche [February 
N. Effective Parasitism. 
What may be included under this term is an interesting phenomenon 
in those relations which a parasite sustains to its host. Under natural 
conditions it may never occur, and here it was observed accidentally. 
Whether or not a parasite can overcome the effects of development in 
a host at the time just preceding an ecdysis, when development is 
liable to be very rapid, is not a very important question, excepting 
when it is concerned with a host stage of very short duration such as is 
not present here. Nasonia, so far as we know, confines its attacks 
exclusively to the puparia of its various hosts; this stage is usually 
of short duration, but not exceptionally short as is the egg stage, 
so that the period of rapid development immediately preceding the 
final ecdysis, being short, would not materially prolong the period 
open to parasitism — that is, the pupal stage —if it in turn were 
likewise open. ‘The following cases are, therefore, of interest mostly 
from the scientific standpoint. The host was Cynomyia cadaverina 
in the stage just preceding the final eclosion, though this fact was 
unknown when the hosts were exposed to the parasites in confinement 
in order to insure a second generation. ‘The parasites were those 
from hibernated larvae, or parents of the first generation. ‘The host 
puparia were formed on April 23, and were thus six or more days old. 
Case I. 'Vhree virgin females of the parasite emerging at 1:30 P. M., 
April 29, 1909, were at once confined separately in vials, each with 
four of the host puparia. Oviposition was not observed. The hosts 
were then six days old; by 9 A. M., May 1, eight of the host puparia 
had excluded adults which were at once released; another adult 
excluded at 11:20 A. M., May Ist, and two more at 8:30 A. M., May 
2d; the single remaining puparium was apparently successfully para- 
sitized by one of the females but upon examination on May 15, 1909, 
no traces of parasites could be found. 
Case II. A pair of adults of the parasite which had mated for the 
first time at 9:45 A. M., April 29, were confined in a vial with eight 
of the host puparia; the female noticed the hosts at once but left them 
and was engaged with the male for a short while. During the after- 
noon, however, she commenced to deposit eggs; at 10:08 P. M., 
April 30, a host fly emerged and again at 10:25 P. M., the same day, 
when the mother parasite was engaged in depositing into another host. 
At 9 A. M., and 7 and 9 P. M., May 1, three host flies emerged, and 
again on May 2, at 11 A. M., and 5 P. M. ‘The remaining host was 
