80 Thirty-second Report on the State Museum. 



LaccopTiilus maculosus Germ Trans. Am. Ent. Soc, IV, p. 399. 



Acilius semisulcatus Aube" lb. p. 401. 



Hydryporus ? oppositus Say lb. p. 393. 



Hydroporus affinis Say lb. p. 391. 



Dytiscus Harrisii Kirby lb. p. 407. 



Laccobias agilis Randell Bost. Journ. Nat. Sci., II, p. 19. 



Philhydrus nebulosus Say Trans. Am. Ent. Soc, II, p. 250. 



Philhydms refiexipeunis Zimm Trans. Am. Ent. Soc, II, p. 250. 



Hydrobius sidicupreus (Say) , Journ. Acad. N. S. Ph., V, p. 189. 



Hydrobius despectus l>ec New Sp. N. A. Coleop., p. 25. 



Hydrobius globosus Say Long-'s Expedition, II, p. 276. 



They are all strictly aquatic species, belonging to the families of DytiscidcB 

 (the first five mentioned) and Hydrophilidce (the last six). For their deter- 

 mination, I am indebted to the kind services of Dr. Le Conte, of Philadelphia. 



The Dytiscidce have an extensive distribution, being found in all quarters of 

 the globe. The peculiar structure of their posterior and middle pair of legs, 

 which are flattened and edged with a row of dense cilia, permit of their swim- 

 ming with great agility, readily ascending to the surface of the water for air, 

 and again diving to the bottom (whence the derivation of their name, meaning a 

 diver), with the greatest ease. In swimming, their hind legs move together, 

 like those of a frog, and by observing this motion, they may be distinguished 

 from the Hydrophilidce, in which they act alternately. They are carnivorous 

 in their habits in both their larval and perfect states, like the mature forms of 

 the predaceous land-beetles — the Carabidce, which they closely resemble in 

 structure, except in their legs. Occasionally they leave the water, climbing up 

 the stem of a water-plant in the evening, whence they take wing, rising almost 

 perpendicularly in the air, ami dropping after their flight upon the surface of 

 water, and at times upon sashes of glass, as glazed garden frames, etc., which 

 they mistake for water. Their locomotion on land is quite limited, from their 

 hincl legs being capable only of a horizontal movement. The species of Lac- 

 cophilus, however, are able to spring a considerable distance. The hybernation 

 of many of the species is beneath moss and lichens, from which they occasionally 

 venture forth, being sometimes seen swimming under the ice ; others maintain 

 a torpid state, buried in the mud. 



In illustration of this family, two of the species mentioned above as occurring 

 in Caledonia creek, are figured, viz., Dytiscus Harrisii Kirby (fig. 2, plate 4), 

 one of the largest of our species, and of common occurrence, and .-I cilius semi- 

 sulcatus (fig. 7, plate 4), a more unusual form. Figure 1, plate 4, represents a 

 larva belonging to this family, believed by Dr. Le Conte, from an inspection of 

 the original drawing, to belong to the genus Gaurodytes. Several examples of 

 it occurred in the Caledonia collections. 



The larvae of these beetles have been called water-tigers, from their preda- 

 ceous habits. They are long, cylindrical, usually with contracted necks, and a 

 flat head, armed with powerful jaws, which they use expertly in seizing and 

 devouring other insects. Comparatively few of the larvae of our species are 

 known. The larva of Acilius semisulcatus may be presumed to resemble that 

 of the European A. sulcatus, shown in fig. 4, plate 4, from an outline figure by 

 Westwood. Of this larva, it is said : " It is extremely insidious in its attacks ; 

 the downward bending of its neck, and the upward turning of its head, inducing 

 it to seize objects above rather than in front of it ; so that when an object is 

 perceived floating on the surface of the water, the larva rises very cautiously 

 until it has nearly reached it, when, by a sudden jerk of the neck, it seizes the 



