ANNULOSA JAVANICA. 33 



froy. Still, however, the Bytisci and Hydrophili were kept close to each other as neighbouring 

 groupes by Linnaeus, Geoffroy, Fabricius, and Olivier, until M. Latreille thought proper to 

 separate them. 



Olivier seems to have well remarked that Degeer's opinion as to the number of joints in the an- 

 tenna? of Hydrophilus piceits being only nine, is founded rather on appearance than on truth, and 

 that the real number corresponds with that of the Bytisci, namely eleven, the only difference 

 being that the eighth and tenth joints are here very minute. Their place is marked by the dis- 

 tances which intervene between what are commonly considered the second and third, and the 

 third and last joints of the clava. The fact however is, that the number of joints in the antennae 

 is in these two stirpes subject to some variation from the typical number, which in Coleoptera 

 is eleven. 



I have already alluded to those two divisions of the maxilla in Hydrophilus of which one cor- 

 responds with what is usually termed the internal maxillary palpus in Adephaga, although it now 

 ceases to be palpiform. In some genera however, such as Spercheus, which come nearest to 

 the Hydradephaga, the outer process of the maxilla is long, slender, and truly palpiform. Fabri- 

 cius accordingly, when he instituted the genus Spercheus assigned six palpi to it, as well as to 

 Bytiscus. The feet, indeed, of the Philhydrida, as well as other points of their external anatomy, 

 their larvae and their habits, all prove their affinity to the Hydradephaga. 



The larva of Hydrophilus piceus is long and somewhat conical, and bears great resemblance to 

 that of a Bytiscus, the body being terminated in both by two filiform processes, which seem useful 

 for the respiration of the insect. One grand difference between them, as Lyonnet has shown in 

 contravention of a curious fancy of M. Frisch, is that the head of the larva of Hydrophilus being 

 adapted to its habit of preying on small mollusca as they float in the water, is inclined towards 

 its back, whereas in the other it has its usual inclination towards the belly. Both larvae are thus 

 carnivorous, quit the water when full-grown, and having made an oval cocoon, undergo meta- 

 morphosis in the earth. 



The Philhydrida appear, when arrived at their perfect state, to be in some degree herbivorous, 

 or at least to lose in a great measure the carnivorous habits of the Hydradephaga ; they seem 

 therefore to indicate an approach towards insects truly herbivorous. Perhaps Hydrophilus piceus 

 is as voracious an animal as belongs to the stirps ; yet we may learn how inferior it is in voracity 

 to an Adephagous insect, from the anecdote recorded by Clairville, on the authority of Dr. Es- 

 per, who having confined an insect of this species in a glass of water with a Bytiscus marginalis, 

 not more than half its size, soon found it yield itself an easy prey to the latter, which having 

 detected a vulnerable part between the head and thorax, greedily devoured it. M. Miger, also, 

 who observed so well the singular manners of this family, and who has given so detailed an ac- 

 count of them in the fourteenth volume of the Annates du Museum, ascertained that the greatest 

 part of the food of the perfect insects is derived from aquatic plants. 



I shall offer the following arrangement of the Philhydrida as an approximation to the natural 



one : 



p Philhydrida 



