330 
Psyche 
[December 
ing male parasites. At first sight, this sex ratio seems contradicted by 
the higher maximum number of male parasites per host. I account for 
this discrepancy by postulating a short emergence season for the male 
pallidus. If, in a host with several male parasites, all the males 
emerged in rapid sequence before the host could die from the effects 
of desiccation, a situation would exist in which relatively fewer of the 
hosts that had carried males would be alive at any one time, but some 
of them could show high numbers of males per host. Other data from 
table 1 agree with this explanation of the sex ratio in that there were 
325 hosts with just females and 244 with just males or with both males 
and females present. Antagonistic to this explanation is the probabil¬ 
ity that over 6 female pallidus kill the host outright so that we do not 
see these in the sample at all. 
Location of Xenos pallidus in the host: 
The Xenos exserted themselves under the edges of the sclerites of 
the second to the sixth abdominal segments posterior to the waist. 
The parasites showed a strong preference for a dorsal position on the 
abdomen, for several probable reasons. First, the parasite could force 
its way out more easily dorsally because the tergites separate when the 
wasp flexes its abdomen, while the sternites are compressed. Second, 
the tergites cover more of the surface of the abdomen than the 
sternites. Third, it would seem that natural selection would select for 
females to locate dorsally because they would be easier for males to 
fly to and mate with, especially if the female were located posteriorly. 
How mature stylopids penetrate the intersegmental membranes of 
the host has not been described. 
No pallidus were located in segment 1 of the host in this study. 
However, Pierce (1909) did find one male protruding between the 
first and second tergites. As seen throughout the following discussion 
male pallidus are characteristically located more anteriorly than 
females. Only 1 female was found in segment 2 and only 1 male in 
segment 6. The maximum number of males under tergites 2, 3,4, and 
5 was 3, 4, 3, and 1 respectively, for males under sternites 2-5 the 
maximum numbers were 1, 2, 2, and 1 respectively. The maximum 
numbers of females under tergites 3, 4, 5, and 6 were 1, 3, 3, and 2 
respectively, for females under sternites 3-6 the maximum numbers 
were 2, 2, 2, and 1 respectively. 
