232 Mr. G. Lewis on 



where guiding-lines are not wanted, and the striae are again 

 almost obsolete ; it lives in ants' nests under stones, and while 

 the insect is in the nest it wanders about within the limit of 

 the burrows in any direction without forcing a cavity for 

 itself. When the stone is raised Eretmotus moves as fast as 

 possible to the edge of a gallery deeper down in the nest, and 

 then, drawing the legs into the sternal grooves, voluntarily 

 tumbles into it and often feigns death at the bottom. Both 

 classes of insects fly to the places where they congregate, and 

 during flight it does not seem that striation can serve a purpose. 

 The habits of Sternocoeh's, also a genus without striae, corre- 

 spond in many ways to those of Eretmotus ; but it is much 

 more dependent on the ants than the other, and, being so, 

 it is to a greater extent unfettered by the external influences 

 which seem to mould into a monotonous similarity the species 

 in the extensive genera Hister and Saprimts. During its 

 dependency on the ants Sternocodis seems to have been free 

 to develop into strange forms, or, at any rate, forms which 

 appear to us fantastic, almost at random, like Paussus ; but 

 both Sternocoeh's and Eretmotus are limited in their distribu- 

 tion to the area inhabited by their host Aphanogaster, while 

 Paussus, associating with ants of various kinds, some arboreal, 

 some terrestrial, has been found in every continent. 



In the Stercoraceous Histeridaj striae are useful provided my 

 estimate of their value is correct, as they all burrow more or 

 less in the ground, and a large number of the Coprophaga 

 are also provided with somewhat similar strige. Amongst the 

 Geodephaga Abax is an instance of an insect with guiding- 

 lines, and Oodes, like so many aquatic species, is without 

 them. In the Dytiscus ^ there is a resemblance to Oodes, 

 and in the female there is a similarity to Abax, and perhaps 

 the striation, if there is any analogous use for it in such appa- 

 rently different insects, is useful to the female when burrowing 

 in the banks of ponds at the time she arranges for the lodg- 

 ment of her eggs. The Hololeptini are flat and formed for 

 working in all directions under loosened bark, and in several 

 species, such as IJololepta procera, Er., and elongata, Er., the 

 striae are as obsolete as in Eretmotus, whose movements are 

 similarly free. In the genus Lioderma (scarcely separable from 

 HololejJta) the species are not all subcortical, but are found in 

 the rotting limbs of the Opuntia and similar vegetals, and they 

 have frequently one complete stria, and those which are inter- 

 rupted are deep. Finally, reference may be made to Abrceus 

 and Acritus, insects without strise, and whose habits lead them 

 to roam freely in Cossus-burrows or under seaweeds on the 

 shore. The Saprini have a different dorsal sculpture, but, as 



