23,6 Schultze: Pachyrrhynchus 613 



tionless for some time. In the dense undergrowth it is very- 

 difficult to rediscover the beetle, since the coloration of this 

 species, as well as that of most of its allies, blends well with the 

 surrounding underbrush. 



In its food habits as described above Pachyrrhynchus confusus 

 may represent an exception and, therefore, no definite conclu- 

 sions should be drawn with reference to other species of 

 pachyrrhynchids and their food plants, since I suspect, from cir- 

 cumstantial evidences, that some species are root feeders. The 

 beetles of this group are found mostly crawling about on the 

 leaves and twigs of plants and their legs are especially adapted 

 for climbing and obtaining a good grip. The appearance of 

 the beetles in walking is spiderlike, particularly so on account 

 of their peculiar markings. The whole structure of the body 

 of all pachyrrhynchids is extremely hard and solid, in fact so 

 solid that one may step on such a beetle lying on the ground in 

 the forest without injuring it. The unusual hardness of the 

 body of these insects seems to be intended as a protection against 

 injury from falls, or from other accidents which may occur 

 during the usual heavy and violent seasonal rains and storms. 

 During such torrential rains many small and swift brooklets 

 are formed, particularly in mountainous districts. Since these 

 beetles are usually exposed and do not seem to hide during rains, 

 they are knocked to the ground or into the water at such times. 

 When this occurs the hard body of the insect with the united 

 and inflated elytra seemsi to act as a float, since the abdomen 

 only partially fills the strongly convex and connate elytra. In 

 order to inform myself in this respect I performed an experiment 

 by placing four living specimens of Pachyrrhynchus confusus and 

 one of P. moniliferus in separate glass jars containing water. 

 All of them floated on the surface and it was plainly evident that 

 the specimens were drawing air under the elytra by raising the 

 apical termination of the abdomen above the surface of the 

 water. Up to six hours after being placed in the water all 

 were still alive and floating about. After twelve hours, one 

 specimen of P. confusus was still afloat and very lively, another 

 was afloat but dead; still another, which was on the bottom, 

 showed slight signs of life and recovered very soon after being 

 taken out. The other specimens were dead on the bottom. 

 Under natural conditions the time of floating would not need 

 to be anywhere near as long as this because the beetle would 

 surely meet some object to cling to in less time than that utilized 

 in the experiment. 



