152 



INTRODUCTJON. 



others consider the Throscid.e, Eucnemidte, Elaterid^e, Cero- 

 phytiDjE, and Cebrioniile as distinct families ; while others prefer 

 to range them all as subfamilies under the Elaterid^e. The 

 Thboscid^e ought perhaps to be separated from the rest by 

 reason of the formation of the anterior coxal cavities and by the 

 close articulation of the prothorax and mesothorax, but the others 

 run very much into each other and may be classed together. If 

 the larvae are considered, however, there are further difficulties 

 in the way, that of Cebrio especially differing from the others, 

 although the larvae of the Etjcnemik".^ are hardly less peculiar in 

 some cases. The table given by Leconte and Horn ('Classi- 

 fication of the Coleoptera of North America,' p. 176) is perhaps as 

 good as any other, and it is the one quoted by Dr. Sharp 

 (' Cambridge Natural History,' vol. vi. p. 260), but it deals only 

 with the perfect insects and is not altogether satisfactory : — 



I. Posterior coxae laminate ; trochanters small. 



i. Labrum concealed ; antennae somewhat distant 



from the eyes, their insertion narrowing the 



front , Eucneminje. 



ii. Labrum visible, free ; antennae arising near the 



eyes under the frontal margins Elaterin^. 



iii. Labrum transverse, connate with the front. 



1. Six ventral segments ; claws simple ; tibial 



spurs well developed Cebrionesls:. 



2. Five ventral segments ; claws serrate ; tibial 



spurs moderate Perothopinje. 



II. Posterior coxae not laminate ; trochanters of 



middle and posterior legs very long Cerophytinje. 



These subfamilies are very uneven in point of numbers, two 

 of them, the Perothopin^e and the Cerophytinje, consisting of 

 only one genus each. Peroihops has usually been included under 

 the EucNEMiNyE and might perhaps still be left in that position, but 

 Oerophytum is distinct by reason of the non-laminate hind coxse 

 and the long trochanters of the middle and posterior pairs of legs. 

 The former of these genera appears to be a link between the 

 Eucnemlnje and the Cebrioninje, while the latter has been con- 

 sidered to have some affinities towards the DASCiLLiDiE, which 

 perhaps are more apparent than real. 



Most of the Elaterin,e and some of the Eucnemin^: possess 

 the power of jerkiug themselves into the air with a sharp click 

 if placed on their backs ; hence the term " click-beetles " and the 

 generic name Elater or " springer." This movement is brought 

 about by raising the presternum until the end of the posterior 

 process rests against the edge of the mesosternum ; on being 

 suddenly released the process slips forcibly into the mesosternal 

 cavity and by the sudden jerk the base of the elytra is made to 

 strike the surface on which the insect is resting, and this, with 

 the elasticity of the body, causes it to fly upwards. 



