PELTOCEPHALA. 
241 
their head, in the form of a buckler, furnished anteriorly 
with frontal plates and short antennse consisting of two 
flattened joints. In the Pachycephales, on the contrary, 
the head is not shield-shaped ; there are no frontal plates, 
and the antennse are of considerable length, composed of 
five or six articulations. 
Tribe 1 — PELTOCEPHAL4 * M. Edwards. 
In all the genera belonging to this section we distin- 
guish a head, a thorax, and an abdomen. 
The head is generally larger than both thorax and 
abdomen together, is of a rounded form, somewhat trun- 
cated posteriorly, and having in the front part two small 
plates stretching across transversely. 
The thorax varies in the different families, sometimes 
consisting of only two articulations, at others of three ; 
and, in some instances, even of four. In some it is com- 
posed of articulations, which present nothing remarkable 
in their structure, whilst in others these are covered with 
plates, or broad flat scales, which resemble very much 
the parts of some insects called the Elytra. 
The abdomen is always very small, and is terminated 
either by two small ciliated plates, or by a body consisting 
of three leaflets. 
The antennse are small, and are only one pair, com- 
posed of two or three short, simple articulations. 
The mouth-apparatus consists of a large w'ell-developed 
sucking-tube and appendages, adapted for puncturing 
the skin of the animals upon which they live as parasites, 
and for sucking the juices of their bodies ; and three pairs 
of foot-jaws, constructed for enabling them to fix them- 
selves upon their prey.f 
Their feet are four pairs, the greater number in general 
being adapted for swimming. 
* Erom Trt\Tr), a short shield ; and ice<pct\ov, head, 
f Vide the more full description of these parts in Caligidce. 
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