CLICK-BEETLES 



257 



FIG. 13-1. Athous rhombeus. New 

 Forest. A, Larva ; B, female 

 imago. 



J/ i /if? nn riles more or less prolonged backwards; with a prosternal 

 process that can he received in, and usually can move in, a 

 mesosternal cavity. Hind coxa with a plate, above which the femur 

 can lie received. Visible ventral segments 'usually Jive, only the 

 if i- initial one being mobile. Tarsi Jive-jointed. This large family 

 of Coleoptera comprises about 7000 

 species. Most of them are readily 

 known by their peculiar shape, and 

 by their faculty of resting on the 

 back, stretching themselves out 

 flat, and then suddenly o-oing off 



t/ O O 



with a click, and thus jerking 

 themselves into the air. Some, 

 however, do not possess this faculty, 

 and certain of these are extremely 

 difficult to recognise from a defi- 

 nition of the family. According 

 to Bertkau 1 our British Lacon 

 murinus is provided near the 

 tip of the upper side of the ab- 

 domen with a pair of eversible 



glands, comparable with those that are better known in Lepi- 

 dopterous larvae. He states that this Insect does not try 

 to escape by leaping, but shams death and " stinks away ' its 

 enemy. The glands, it would appear, become exhausted after the 

 operation has been repeated many times. The extent of the leap 

 executed by click -beetles differs greatly ; in some species it is 

 very slight, and only just sufficient to turn the Insect right side 

 up when it has been placed on its back. In some cases the 

 Insects go through the clicking movements with little or no 

 appreciable result in the way of consequent propulsion. Although 

 it is difficult to look on this clicking power as of very great value 

 to the Elateridae, yet their organisation is profoundly modified so 

 us to permit its accomplishment. The junction of the prothorax 

 with the after-body involves a large number of pieces which an- 

 all more or less changed, so that the joint is endowed with greater 

 mobility than usual; while in the position of repose, on the other 

 hand, the two parts are firmly locked together.' The thoracic 

 stigma is of a highly remarkable nature, and the extensive 



1 Arch. Naturgesch. xlviii. 1, 1882, p. 371. 

 VOL. VI S 



