EXTERNAL STRUCTURE. 



5 



as in the Hymenoptera. In some cases, e. g. Homalium 

 (Staphylitstidye), ocelli, or small complementary eyes, consisting ^ 

 of single lenses, are present. The existence of these ocelli is 

 usually considered to indicate that the form is primitive and to show 

 that it hears a close relation to its remote ancestor, the purely 

 hypothetical and probably mythical Protocoleopteron. 



The antennas, are appendages of very varied length and shape, 

 which are inserted in front of, or, more rarely, between the eyes ; 

 in the Rhynchophora they arise from the rostrum either further 

 from, or nearer to, the base ; very rarely they consist of a single 

 joint (Articerus); in a considerable number of the Paussid/E and 



Fig. 4. — Forms of antennae, a, filiform (Cicindela); b, clavate 

 {Colon) ; c, irregularly serrate (l)orcatoma) ; d, flabellate (Acneus) ; 

 e, sen-ate (Ludius) ; f, moniliform (Rhi/sodes) ; g, irregular 

 (Dineutes) ; h, abnormally clavate {Adranus) ; i, lamellate 

 (Lachnosterna) ; j, lamellate {Lucanus). , (Mostly after Leconte 

 anrl Horn.) 



in Adranus they are 2-jointed, but in the great majority of the 

 Coleoptera they are 11-jointed. The different forms of the 

 antennae have been largely used in classification, but although 

 valuable in this respect, they are not in all groups (e. g. the Clayi- 

 cortstia) to be entirely relied upon ; roughly speaking they may be 

 classed under four heads : — ■ 



1. Filiform: where the joints are more or less elongate and not, 

 or scarcely, enlarged towards the apex ; if they taper they are called 

 setaceous. If the joints do not differ much in size and are more or 

 less rounded, like beads on a necklace, the antennas are called 

 moniliform. 



