192 THE THEORY OF EVOLUTION 



Club Beetles (Clavigeridae) on account of the peculiar 

 form of their antennae. These differ from their nearest 

 relatives, the ' Feeler Beetles ' (Pselaphiden) by a series 

 of adaptive characters fitted for the true guest conditions ; 

 by the marked development of the first upper rear 

 segments, which bear a broad and deep exudation groove; 

 by the yellow hair bunches on the hinder parts at the 

 sides, or on the wing cover points ; by the shortened, 

 thickened, and very variedly formed antennae, as also 

 by the retrogression of the feelers which, as organs of 

 independent search for nutrition, have become useless. 

 Classic examples of Club Beetles are our small yellow 

 ones (Claviger testaceus) as are the great Madagascar Club 

 Beetles with stag-horn feelers (Mirodaviger cervicornis). 

 We know already at present forty-two systematic genera 

 of Clavigeridse with 124 species, whose generic and family 

 characters are plainly myrmecophil adaptive characters. 

 There is, furthermore, one particular beetle family 

 the Paussidse or Feeler Beetles which are all Ant guests 

 but nevertheless belong to different biological classes. 

 By far the most of them are true guests which are 

 provided with multiform reddish yellow hair bundles, 

 exudation grooves, and exudation pores which are licked 

 by their hosts. Their very thick and only two-limbed 

 feelers present the most varied and grotesque forms, 

 which, however, all like the exudatory organs just 

 mentioned stand in the most intimate connection 

 with their true guest relationship. The species and 

 genera of the Paussidse and the whole family itself are 

 what they are by virtue of their myrmecophil character. 



