HVDROPIIILIDiE. 



129 



in Gyrinus) which appear to aid respiration ; in the case of Berosus 

 the larva is broad, fusiform, and furnished at the sides with very 

 long and slender branchial appendages, some of which are almost 

 as long as the whole abdomen ; the larva of Helophorus is parallel- 

 sided, with the prothoracic segments chitinous and with chitinous 

 plates on the abdomen, without lateral processes, but with two 

 very long 3-jointed cerci at the apex ; the larva of Sphceridium is 

 grub-shaped, considerably narrowed in front, with an extremely 

 small head, and a broad anal segment, with four short teeth at the 

 apex, and two conical appendages on each side ; it is practically 

 legless ; that of Cercyon differs little but in minor particulars. 

 jSpercheus possesses a very distinct larva, broad and more or less 

 ovate, with a very large head and powerful jaws, with hairy pro- 

 tuberances at the sides of the abdominal segments, no distinct 

 anal appendage or cerci, and with very different mouth-parts to 

 those found in the allied genera. In Octhebius the larva possesses 

 a developed extra mouth-segment, and short 2-jointed cerci. 



From these very brief descriptions it will be seen that there is 

 no other family that possesses such heterogeneous larva?, and it is 

 a question whether the family ought not to be subdivided on their 

 characters ; in any case it might be of advantage to consider the 

 Spercheen^e as separate. Ganglbauer (Die Kafer von Mittel- 

 europa, iv, 1, p. 152) divides the family into subfamilies largely 

 on these larval characters, and his table is well worth consulting 

 as so many of the European genera are found in the tropics. 



The young larva of Spercheus and its habits are described by 

 myself (with figures by the Rev. A. Matthews, in Ent. Monthly 

 Magazine, xix, p. 79). The female carries her eggs in a bag 

 attached to the abdomen until they are hatched, and she can 

 produce several batches of eggs in succession without the inter- 

 vention of the male. The larvae are carnivorous and in confinement 

 prey upon one another ; they walk upon the surface of the water, 

 back downwards, like the perfect insect. The latter possesses a 

 rather strong stridulatory organ. 



In the perfect state the members of the family feed on de- 

 composing vegetable matter, but the larvee of the Hydrophilitoe 

 appear to be essentially carnivorous and predaceous ; their habits 

 are, in some cases, very interesting, but we have no space here to 

 discuss them. 



I. Posterior tarsi with the first joint very short, 

 often not visible from above, 

 i. Second joint of posterior tarsi elongate, longer 

 than third; first joint very short ; pronotum 

 at base as wide as elytra. 



1, Posterior tarsi oar -shaped ; metasternum 



prolonged into a sharp elongate spine .... Hydrophilinje. 



2. Posterior tarsi not oar-shaped ; metasternum 



not prolonged into a spine Hydrobiin^e. 



K 



