I\TI{ODUCTIOX, 



Fig. 4. 



Small portion of 

 ej'e bisl'ly niag- 

 nitied. 



Fit 



The eyes are very variable ; rarely as in Anillus, and in many cave 

 insects, they are wanting ; they are made up of a large 

 number of small lenses, which vary very much in 

 number and size : in some groups, as for instance 

 Languria, their formation affords good specific cha- 

 racters, the eyes being said to be finely or coarsely 

 granulated, accordingly as the number and so the indi- 

 vidual size of the lenses is greater or smaller : in some 

 families additional eyes are found consisting of one or 

 two simple lenses ; these are termed ocelli, and are 

 situated on the vertex behind the true eyes ; they occur in the Homa- 

 liina, &c. Occasionally the eyes are partially or almost entirely divided 

 by a corneous ridge as in Dorcus and Th7'oscus, or they may be entirely 

 divided, so that there are two eyes on the upper surface of the head and 

 two on the under surface as in Gyrinus and 

 AmpTiio2)s. The head is often furnished with 

 long erect setai arising from pores or special 

 punctures ; their function is probably the same 

 as the whiskers of the feline tribe of animals, 

 as they seem especially developed in those 

 beetles that are carnivorous and nocturnal in 

 their habits, e.g. the Carabidaj. Dr. Horn in 

 his valuable paper on this family has made 

 great use of those that are found on the 

 surface of the head near the eyes in the 

 classification of the Harpalinte, those genera that possess one such seta 

 being classed under his group H. unisetosoi, and those that possess two 

 under his other great group H. lmetoi>ie. 



In some families the head is furnished with largo horns and other 

 appendages, which are especially found in the male, and arise chieliy 

 from the clypeus : these are particularly noticeal)le in the Lamellicornia ; 

 with the exception, however, of Copris and one or two other species none 

 of our indigenous beetles possess them in a marked degree. 



Tlie antennce are joiiited appendages which are usually inserted in 

 fi'ont of, more rarely between, the eyes : in the Ithynchophora they arise 

 from the rostrum either further from or nearer to the base; they are 

 extremely variable in shape ; a very full description of the various forms 

 which they present is to be found in Leconte and Horn's " Classification 

 of the Coleoptera of North America," Preface, pp. xii and xiii ; those 

 forms that chiefly require notice are as follows : — 



1. Filiform or thread-like, in which the joints are elongate and cylin- 

 drical^ and the apical ones not or scarcely enlarged ; if they become more 

 slender toAvards the tip they are called setaceous : such antenmc are one 

 of the chief characteristics of the Carahichu and Dytlscida'. 



2. C/avifonn or clavale, in which the apical joints are enlarged and 

 form a more or less distinct knobbed club ; sometimes the club is 

 gnulual, in other cases sudden and abrupt : in tlic latter case the 

 antenn;e are said to be capilate. 



Side view of head of Gyrinus. 



