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SEXUAL CHARACTERISTICS OF THELIA 563 
jointed near their bases. The melanin is very irregularly dis- 
tributed, always being absent about the bases of the spines and 
also in larger irregular areas, which produces a mottled appear- 
ance over the whole nymph (figs. 15 and 16). Parasitized adults 
possess none of these juvenile characteristics, but males affected 
by Aphelopus assume female coloration through the loss of male 
characteristics and the addition of those of the adult female 
integument. 
Female Thelia are larger than males. Thus the pronota of 
111 normal females, measured with a micrometer caliper from 
the tip of the horn to the end of the posterior process, averaged 
TABLE 1 
VOMBER OF| AVERAGE AVERAGE 
INDIVID- LENGTH OF} WIDTH OF 
UALS PRONOTUM | PRONOTUM 
mm, mm, 
Normal males.......... th ge fa 11.55 4.73 
Parasitized males shards. craaiiia or F complete 
change to female coloration........ 98 12.24 5.03 
Parasitized males with male eu loncinon still pre- 
dominating. . ay, es a Ror aa cee leucine aon ise 29 11.68 4.85 
Total senesced ales shore aS ay See Sees et 127 patil 4.98 
Normal females. . Soetins itt 13.39 5.41 
Parasitized femelle with pecdediy Rodieae - Ovi- 
J OXSISITLHON ES se ence maaeehis Ciao aNd Bec amanactor Rares 100 Se wel 5.33 
13.389 mm., and the average width across the humeral angles 
was 5.41 mm. (table 1). Corresponding measurements on 114 
normal males gave 11.55 mm. as average length and 4.73 mm. 
as the width. This shows that the pronota of normal females 
are about 15 per cent longer and broader than those of normal 
males. If, now, we examine parasitized males with a well- 
defined change in color (medium to complete), we see that they 
are both longer and wider than normal males, the increase being 
about 6 per cent. That this is due to the action of the parasites 
is shown by the fact that in males parasitized late in their on- 
togeny (those with male coloration still predominating) we find 
but a slight increase in size. Only when large parasites are 
JOURNAL OF MORPHOLOGY, VOL. 32, NO. 3 
