286 



BULLETIN OF THE BUREAU OF FISHERIES. 



lamellae; those in the terminal row are large and broadly ovate, in the second row much smaller and 

 narrlowy obovate, and in the third row triangular with all three margins concave. The sides of the ros- 

 trum are indented about one-third of the distance from the tip to the base, and the broader basal portion 

 is fringed with setse along its lateral margins and several transverse rows across the top. The epicranial 

 suture is about one-fourth the length of the head, and each fronto-antennal suture is curved like the letter 

 S, joining the lateral margin of the rostrum in front of the antennae. 



The prothorax is one-half wider than long, the mesothorax three times, and the metathorax four 

 times as wide as long. The abdominal segments decrease regularly in width and the last one takes the 

 form of a triangle with a bluntly rounded tip, its length more than three times its width. To its center 

 on the ventral surface are hinged the cerci close together on the median line. Each is two-jointed, 

 slender, tapering, and about one-third as long as the body. 



The antennae are four-jointed, the second and third joints the same length and much longer than the 

 first and fourth. The mandibles are curved and deeply grooved along the inner margin ^ They are 

 attached not to the corners of the frontal margin as usual, but to the ventral surface of the head posterior 

 to the bases of the antennae, and their bases are not visible in dorsal view. Furthermore, they are attached 

 at an angle, so that instead of shutting past each other like a pair of scissor blades they shut in diagonally, 

 their tips just meeting against the ventral surface of the rostrum inside the fringe. Each maxilla con- 

 sists of a stout basal joint armed with three large setae on its ventral surface and a three-jointed palp, 

 whose second joint is three-fourths as long as the first, and the third half the length of the second and 

 tipped with two minute setae. The labium is wider than long, the palpiger heavily armed with stout 

 setae on its ventral surface; there is no ligula. The labial palps are two-jointed, the terminal joint a 

 little shorter and more slender than the basal and tipped with two tiny setae. These palps are nearly as 

 long as the maxillae and are sparingly armed with setae. The tarsal claws are alike, very long, slender 

 and acuminate. 



Pupation. — The species reared by Needham and Williamson (1907) pupated without making any 

 chamber, while another species (septentrionalis) found by Matheson (1914) in the Salmon River near 

 Truro, Nova Scotia, constructed a pupal chamber out of pellets of sand under flat rocks on the river 

 bank. 



Description of the pupa. — None of the larvae of the present species could be induced to pupate, and 

 we have to be satisfied with a general description applying to the genus as a whole. The pupa is white 

 in color, except the eyes, which are pigmented. The head is withdrawn into the prothorax and is well 

 provided with short and strong styli. The anterior margin of the pronotum is also armed with a row of 

 short styli, and others are scattered over the dorsal surface of all the thoracic segments. In the abdomen 

 the posterior margin of each segment is raised into a transverse ridge, which is armed with a row of styli. 

 The abdomen ends in a pair of large and long spines or cerci, which help to support the pupa inside the 

 chamber. Matheson (1914) said that the species he studied rested upon its back in the pupal chamber, 

 but the row of stout styli along the front of the pronotum and the strong cerci would indicate that they 

 are used to support the pupa at least a part of the time. If this be true, then it rests also upon its ventral 

 surface with the body arched strongly upward like the other pupae. 



Habits of the adult. — The hind legs are rather weak, but are heavily fringed with swimming setae, 

 so that the beetle moves through the water quite rapidly and shows considerable agility. On the land 

 it is not as clumsy as many of the dytiscids but walks farily well and can jump a short distance. These 

 beetles are rather difficult to watch, because they stay among the filaments of the algae most of the time. 

 The only thing they were seen to eat was Chironomus pupae. 



Description of the adult. — General form an elongate oval, slightly narrowed posteriorly; width 

 considerably more than half the length; length 4 mm., width 2.5 mm. The dorsal surface is uniformly 

 black, with the head and legs reddish-brown; antennae dark brown, the base lighter in color. Thorax 

 and elytra finely and evenly punctured and covered with scattered soft hairs. Both the adults and the 

 larvae of these beetles furnish excellent fish food. 



Genus LACCOPHILUS Leach. 



Laccophilus (Leach, 1817, p. 69). 



These are small but very active beetles whose bodies are considerably depressed 

 and usually spotted in color. The hind legs are well developed, and they are strong 



