cxlii FAUNA HAWAIIENSIS 



I believe, have only arboreal habits. The fourteen species of Mesothriscus and twenty- 

 six of Metromenus in general resemble Atelothrus in their habits, some being arboreal 

 either living beneath bark or in moss or in cavities in rotten wood or in tree-ferns, or on 

 the ground, in or beneath logs of wood, and but rarely under stones. A few species in 

 both genera are found in wet forests by day on the flowers of Astelia, and some, like 

 Metromenus mutabilis, hide in numbers at the bases of the leaves of this plant or (like 

 M . palmae) o{ Ffeycinetia. Occasionally at night we have seen some of the Anchomenine 

 Carabidae devouring caterpillars, and it is probable that these form a large part of their 

 tabulum. Their fondness for Acacia koa, which so generally is attacked by caterpillars 

 of Scotorythra, leads me to suspect that this genus supplies many of them with food. 

 The beetles themselves are in some cases very long-lived, even under unnatural conditions 

 in captivity, and I have been struck with the fact that while the larvae of many of them 

 are found in the same situation as the adults, the latter generally are much more 

 common. The species of Mecostomus and Mecomenus are not well known, but they are 

 apparently terrestrial species. 



That the Oahuan bird Oreomyza maculata apparently hunts specially for the 

 Carabidae of the genus Derobroscus has been mentioned above, and I have found 

 remains of Colpocaccus hatvaiiensis in dissecting the rarer bird Viridonia on Hawaii, 

 and this latter genus of beetles and some allied genera in other birds. Metromenus, 

 Colpocaccus and other of the genera emit an unpleasant odour, and when a colony 

 of C. tantalus is disturbed, under certain conditions of weather, the vapour given off 

 becomes easily visible, and in ammonia gas produces dense white fumes. 



Generally speaking one may say that of these Carabidae those species with the 

 most diverse habits are the most abundant, but a few that are more constant in habits, 

 e.g. Metromenus palmae and M. mutabilis, are also very common. It seems clear that 

 the scarcity of some species is due to the fact, that they are very particular as to the 

 condition of their habitat, and that these conditions can rarely be found. Such species 

 cannot but be individually weak, even though they are generally present, when the 

 right conditions occur. Others like M. paltnae and mutabilis above mentioned, though 

 restricted to certain environments, find the right conditions commonly. Yet other species, 

 which apparently are rare, and yet, so far as one can judge, affect conditions that are 

 commonly met with, may be thus rare because the conditions which are really suitable 

 are not common, but we are not able to distinguish between the suitable and unsuitable. 



The four genera of Pterostichini cannot at all be distinguished from one another by 

 their habits, but there is much difference between some of the species in this respect. 

 Generally speaking they agree in these with the Anchomenini. Many are arboreal 

 being found only under bark, or moss, or in dead branches of growing trees, and usually 

 those of terrestrial and arboreal habits are quite constant in these habits. Some of the 

 ground-frequenting species are not uncommonly found in decayed stems of tree-ferns, 

 and a few, like Metrothorax deverilli, are found beneath bark or moss on trees, in hollow 



