PELTOCEPHALA. 241 



their head, in the form of a buckler, furnished anteriorly 

 with frontal plates and short antennae consisting of two 

 flattened joints. In the Pachycephales, on the contrary, 

 the head is not shield-shaped ; there are no frontal plates, 

 and the antennae are of considerable length, composed of 

 five or six articulations. 



TRIBE 1PELTOCEPHAL4* 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 antennae are small, and are only one pair, com- 

 posed of two or three short, simple articulations. 



The mouth-apparatus consists of a large well-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. 



* From Trt\Tr), a short shield ; and /c^aXov, head. 



f Vide the more full description of these parts in Caligida. 



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