SEXUAL CHARACTERISTICS OF THELIA 533 
a time when the males should be at their maximum. Exami- 
nation of the gray individuals showed that some were altered 
males, each of which, when dissected, revealed the presence of 
thirty-five to fifty larvae in its abdomen. A great deal more 
material was observed and collected in the summers of 1914-17, 
and it is upon this material that the present paper is based. 
We are first concerned with the external changes which the 
parasites bring about in their host, and to this I shall attempt 
to confine the present study; secondly, with the internal changes 
produced, to which I shall at times refer and upon which it is 
hoped more data can soon be procured; and, thirdly, to the 
nature of the parasites themselves, about which a number of 
facts are now known and are briefly given in part 5. 
2. SYNOPSIS OF PREVIOUS PAPERS ON THE SEX OF ARTHROPODS 
- Experimental observation on the relation between germ gland 
and soma in insects goes back to Oudemans (’98), who castrated 
both male and female caterpillars of gypsy-moths. Although 
the objection may be raised that the majority of the larvae were 
castrated only on one side, yet neither these nor the more 
important, completely castrated individuals showed in their 
adult form any deviations from the normal structure or instincts. 
Morphological and psychological sexual characteristics were not 
in the least altered by the absence of the gonads. Oudemans 
reviewed in his paper many of the striking cases of gynandro- 
morphism then known and used these as additional evidence to 
prove that in insects the soma is independent of the germ plasm 
in its development. Cramptons’ paper (’99), while not dealing 
with the castration of Lepidoptera, has an interesting bearing 
on the question of sex in the insects. He grafted the pupae of a 
number of our common moths in pairs arranged in tandem and 
side by side. The members of a pair were often opposite sexes 
of the same species, others were opposite sexes of different spe- 
cles. In some cases the ovaries of the female component grew 
into the male portion of the graft, and yet in none of the cases 
in which the imaginal stage was successfully reached were the 
colors of the components in the least altered from the normal. 
