VARIATION, AND ITS CAUSE. 57 



green, and a very few purple, while one or two are marked with 

 a black cross on the elytra, like that of Eudema. 



A most conspicuous example of an exception to a general 

 rule is found in the strange Beetle which is shown below, and 

 which seems quite out of its place, looking, in fact, as if it 

 ought to have been among the Scaritides. Still, if the reader 

 will compare the structure of the legs of the Scaritides with 

 those of the present insect, he will see that they must belong 

 to two widely different groups. The front legs of the Scari- 

 tides are powerful, palmated, notched, and spiky, while those 

 of the Dioctes are comparatively feeble, slender, without any 

 palmations, and entirely spikeless. There are many other 

 distinctions, but this is the principal. 



Fig. 22. — Dioctes Lehmannii. 

 (Black.) 



The chief points in the shape of this insect are the enormous 

 development of the head and thorax, and the very small size ot 

 the rounded abdomen. The jaws are absolutely gigantic, and 

 look as large in proportion as the bill of the Toucan or Hornbill 

 does to the body of the bird. Then, in order to supply attach- 

 ment to the large muscles which move these jaws, the head must 

 necessarily be increased in size, and that in its turn requires a 

 strong thorax to support it. 



The legs of this insect are very long in proportion to its 

 body, and are liberally supplied with hair. The colour is uni- 

 formly black, and the elytra are only marked by rows of very 

 faint punctures. This Beetle is a native of Central Asia, and 



