Insects, etc., of Caledonia Creek. 81 



object with its jaws, and immediately drags it under water ; if it still struggles, 

 the larva endeavors to despatch it by repeated jerkings of the lead. When in 

 the water they may constantly be seen jerking themselves in every direction, 

 probably for the purpose of seizing upon other minute insects." (Westwood, 

 loc. cit., I, p. 102.) 



Another species of this genus — Acilius mediatus of Say — will probably be 

 found at Caledonia, as it is quite a common species. 



Of the genus Hydroporus, of which two species were taken at Caledonia, 

 seventy-seven species are described from the United States.* The individuals 

 of the several species are also usually quite abundant. 



The family of Hydrophilidce is named from the principal genus, Hydrophilus 

 — the name from the Greek, meaning a lover of water. The larvae are preda- 

 ceous, eagerly catching and devouring other insects. In their perfect form, as 

 beetles, they live almost wholly on vegetable food, and are, therefore, valuable 

 agents in the purification of our waters, from their feeding on refuse and decay- 

 ing vegetable matter. Their legs are similar to those of the preceding family, 

 but they do not swim with the same facility. 



An interesting feature of some of the species of Hydrophilidce is the cocoon- 

 like envelop which the female spins for her eggs — fifty or sixty in number. It 

 is composed of silk, proceeding from two large silk glands, like those of many of 

 the Lepidoptera, through a pair of external spinnarets. The cocoon has been 

 compared in shape with a turnip, having a horny projection which serves as a 

 respiratory channel for the young larvae after they are hatched. In some spe- 

 cies, the cocoon is attached to aquatic plants, and in others it is borne about by 

 the beetle, upon the under surface of the abdomen. In fig. 5, plate 4, the form 

 of the cocoon or egg-envelop of Hydrophilus piceus Linn., a European species, 

 is shown : figure (j is the same cut open to show the arrangement of the eggs 

 contained within. The figures are copied from drawings by Riley, given in Le 

 Baron's Fourth Annual Report on the Insects of Illinois. 



Hydrophilus triangularis Say — one of our common species and of frequent 

 occurrence in ponds, is represented in figure 9, of plate 4, in illustration of this 

 family. The figure is from the same source as above cited. 



While all the species of these two families, in both their larval and perfect 

 stages, furnish desirable food for fishes, it is proper to state that many of their 

 larvae also prey upon very young fishes. It is not probable, however, that in 

 pisciculture serious evil need be apprehended from the presence, unless in very 

 unusual number, of predaceous larvae. From the rule of general antagonism 

 prevailing throughout nature — of devouring and being devoured in turn — final 

 good undoubtedly results, in the succumbing of the weaker forms, and the sur- 

 vival of those best fitted to accomplish the objects of their creation. 



DIPTERA. 



The larvae of two species of small flies, allied to the musquitos and gnats, were 

 abundant in the plants collected at Caledonia in March, 1877, and very abun- 

 dant in a package containing additional material, from the same source, received 

 in February, lo78. They are, to all appearance, congeneric with the larvae 

 figured by Packard, Smith, Grlover and others, as those of Chironornus. 



The perfect insects of this genus are musquito-like in appearance, having 

 beautifully feathered, usually triangular, antennae, a large thorax, small abdo- 

 men and wings, and long, delicate legs. A large number of North American 

 species are embraced in the genus, so that it would not be proper, with our 



♦Crotch : Revision of the Dytiscidae of the United States. Trans. Amer. Ent. Soc., iv, p. 383. 

 6 



