SEXUAL CHARACTERISTICS OF THELIA 607 
any of the qualitative changes previously described. Female 
secondary sexual characteristics are stimulated to development 
in male Thelia containing Aphelopus larvae, and these charac- 
teristics are not only those of size, coloration, and pattern, but 
metabolic characteristics also. The change of male metabolism, 
I believe, is necessitated by the demand for food by the parasites. 
The metabolic differences between male and female tissues are 
known in many groups of the animal kingdom. These differ- 
ences are associated primarily with gamete production, the act 
of fertilization, and the rearing of the young. ‘The female must 
not only provide material for her somatic needs, but she must 
often store up a large quantity of food in the formation of ova or 
furnish it to the growing embryo. The male produces micro- 
gametes generally in immense numbers and actively seeks the 
female, and, with the fertilization of the eggs, often his function 
is performed. The sexes of Thelia exhibit many differences 
associated with gamete production. The female develops less 
rapidly than the male, but the resulting adult is of greater size. 
Upon reaching the imaginal stage only minute ova are present 
in the gonads, but the tissues have the capacity for the storage 
of reserve food, and this storage continues for several weeks, 
during which time a large amount of yolk and fat is accumulated 
due to steady feeding and low oxidation of the ingested food. 
Male Thelia develop more rapidly and appear in July, generally 
before any females are to be seen. They are already sexually 
mature at molting and are much more active than females, 
flying or jumping more easily upon being disturbed. This 
activity is doubtlessly associated with seeking the females in 
mating. The males are also less long-lived than the females, 
disappearing in late summer, whereas the females are still abun- 
dant in the fall. The more rapid development of the male, the 
rapid division of the spermatogonia, the short growth period of 
the spermatocytes, early sexual maturity, great activity, and 
earlier death indicate high'’metabolism and high oxidation. As 
the season progresses, the gonads of the male become smaller, 
many cysts of germ cells undergo degeneration, and the stored 
adipose tissue surrounding the testes decreases in amount. 
