BEETLES. 389 



fields during the night. The insects of this family respire under water from a supply 

 of air which they carry about attached to the pubescence of the under surface of their 

 bodies ; and this air, which appears like a sheet of silver beneath the beetle when in the 

 water, is often renewed by the insect coming to the surface. 



The life history and habits of some of the Hydro philida? are interesting in the 

 extreme because of the nest which the females construct and in which they deposit 

 their eggs. This cocoon-like nest is produced by the hardening of a gelatinous secre- 

 tion from accessory glands of the sexual organs of the females, and in it are deposited 

 from twenty to over one hundred eggs, according to the species. The cocoon is fast- 

 ened by some of these beetles to submerged vegetation, by others it is left to float on 

 the surface of the water, and the females of still other species carry their cocoon about 

 beneath them, fastened between the posterior coxae and steadied by the hind legs, until 

 the young larva? have hatched. The larvae are recognized, according to Professor 

 J. C. Schiodte, by their " claw-formed tarsi, which are sometimes wanting, the ter- 

 minal pair of stigmata, the free projecting mouth-parts, the very short joint membrane 

 of the maxilla?, the connate clypeus and absence of the labrum, the sharp, sickle-formed, 

 imperforate mandibles, the absent or sharp ligula, the want of a neck on the extended 

 head, and the very short, unarmed anal segment." The larvae when first hatched often 

 prey upon one another in the same cocoon ; later they feed upon insects which fall 

 into the water, and upon snails. In the case of the larvae of Hydropliilus piceus, which 

 eat common house-flies with avidity, the mode of feeding is curious. Seizing the fly 

 in its jaws, the swiftly swimming larva seeks some place where it can eat it in quiet 

 and security. Having found a suitable place, it rests upon a piece of grass or leaf and 

 projects the head above the surface of the water, holding it perpendicularly. In this 

 position it chews the fly into a pulp, using the antennae as mouth-parts during the pro- 

 cess, and sucking the juices of the fly down its throat, which, during the mastication, 

 acts as a tunnel to catch the juices crushed from the fly. The head is apparently held 

 above the surface of the water in order that the juices of the prey shall not be diluted 

 by the water. After the juices have been sucked from the fly its chitinous parts are 

 rejected, at least by young Hydrophilus larva?, in the same way as like innutritions 

 parts of its prey are rejected by scorpions after they have drawn the 

 juices from it. Pupation takes place in the ground. 



Among the small species of Hydrophilidae are a number of very 

 convex form, terrestrial habits, and having the middle and hind tarsi 

 with the first joint elongated. Of these small forms species of Sphceri- 

 dium have a narrow mesosternum and elongated scutellum. 8. scara- 

 bceoides is black, with yellow legs, a yellow spot on the tip of each 

 elytron, and just in front of this yellow spot a larger blood-red one. FIG. 462. 



_ . . . .-,-, T-i i dium scarabtEoidcs. 



It lives in cow-dung in Jiurope, and a single specimen, perhaps acci- 

 dental in occurrence, has been reported from Canada. The larvae of Sphceridium 

 and of Cercyon, related genera, live 'in moist earth and in dung, and prey upon 

 dipterous larvae. 



Hydrobius and Phylhydrus include closely related aquatic species which have the 

 middle and hind tarsi not compressed and with the first joint short, and in which the 

 pro thorax at the base is as wide as are the elytra. The last of the five exposed ventral 

 segments is entire, and the antenna? are nine-jointed. In Hydrobius the last joint of 

 the maxillary palpi is longer than the third joint. In Phylhydrus the last joint is 

 shorter than the third. H. ylobosus and P. rotundatus are similar appearing, smooth, 



