CERTAIN PARASITIC INSECTS. 97 
what pointed. The third segment of the thorax is as wide 
as the head, and the legs are thick, the femora being broad. 
It is allied to C. piceum Denny, which in Europe lives on 
the Sandwich Tern. 
The most degraded genus is Gyropus, of which Mr. C. 
Cook has found G. ovalis of Europe abundant on the Guinea 
pig. A species is also found on the porpoise ; an interesting 
fact, as this is the only insect we know of that lives parasit- 
ically on any marine animal. 
The genus Goniodes is of great interest from a morpho- 
logical and developmental point of view, as the antenne are 
described and figured by Denny as being "in Fig. 29. 
the males cheliform (Fig. 29, a, male; b, fe- / 
male); the first joint being very large and 
thick, the third considerably smaller, recurved 
towards the first, and forming a claw, the 
fourth and fifth very small, arising from the 
back of the third.” He farther remarks, “the 
males of this [ G. stylifer, which lives on the 
Turkey] and all the other species of Goniodes, 
use the first and third joints of the antenne 
with great facility, acting the part of a finger 
and thumb" (Denny's Monographia Anoplu- Antenne of Goniodes. 
rorum Britannie, 1842, p. 155 and 157). The antenne of 
the females are of the ordinary form. This hand-like struc- 
ture, is so far as we know, without a parallel among insects, 
the antennz of the Hemiptera being uniformly filiform,* and 
from two to nine-jointed. The design of this structure is 
probably to enable the male to grasp its consort and also . 
perhaps to cling to the feathers and hairs, and thus give it a 
superiority over the weaker sex in its advances during court- 
ship. Why is this advantage possessed by the males of this 
genus alone? The world of insects, and of animals generally 
abounds in such instances, though existing in other organs, 
* Except in Ranatra and Belostoma where they are disposed to be flabellate, 7.4. 
rudely pectinated on one side 
AMER. NATURALIST, VOL. IV. 18 
