WATER BEETLES IN RELATION TO PONDFISH CULTURE. 



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with dark brown along the anterior and lateral margins and much lighter brown along the posterior 

 margin. On the lateral margins of all except the prothorax there is a second narrow dark line above the 

 one along the edge, and on the first six abdominal segments a third much wider line and a fourth very- 

 narrow line. On the prothorax a narrow brown band runs from the anterior margin nearly to the poste- 

 rior margin on either side of the mid line. These bands widen and diverge slightly posteriorly. Begin- 

 ing again in the mesotharax and a little wider, they extend to the posterior margin of the seventh, 

 abdominal segment, being interrupted by narrow yellow transverse lines near the posterior margin of 

 each abdominal segment. Outside of these bands and separated from them by a longitudinal yellow 

 stripe is a wider brown band on either side, beginning with the third and ending with the seventh abdom- 

 inal segment. All these brown bands deepen in color posteriorly and the two on either side fuse just in 

 front of the transverse yellow line in each segment. 



On the central bands are small areas much deeper in color, a pair at the anterior margin of each 

 segment. Those on the mesothorax and metathorax and the first two abdominal segments are minute and 

 are partially concealed beneath the posterior margin of the sclerite in front. On the seventh segment the 

 brown bands fuse across the posterior two-thirds of the segment, leaving only the mid line yellow. On 

 the eighth segment the entire surface is yellow, with a narrow black band at the extreme posterior end 

 and the two tracheae showing as a dark longitudinal line on either side. The fringes along the lateral 

 margins of the seventh and eighth segments are dark brown, almost black; the cerci are a much lighter 

 brown. On the legs the edges of all the joints are pencilled with dark brown. The entire under surface 

 is yellowish- white, except the seventh segment, which is tinged with brown. There is a fringe of silky 

 black hairs along the ventral margins of the abdominal pleura on either side and scattered hairs across 

 the posterior margin of the second, third, fourth, and fifth abdominal segments. The spiracles and the 

 tubes connecting them with the tracheae are jet black; those of the seventh abdominal segment open on 

 the ventral siu-face. 



Head an elongate trapezoid, one-half longer than wide, widest through the eyes, narrowest at the 

 posterior margin, with straight sides. Epicranial suture nearly half the length of the head; frons trian- 

 gular with curved sides, the anterior margin bordered with a thick fringe composed entirely of short stout 

 spines, arranged in several rows. There is a transverse row of long setae just in front of the dark spot on 

 the frons. Between the fringe and this row of setae the surface is covered with scattered minute spines. 

 Around the dark spot and through its center longitudinally are short setae. 



The antennae are six-jointed, the first, third, and fifth joints stout and about the same length, the 

 second and fourth joints almost spherical and less than one-fourth as long, the terminal joint a narrow 

 fingerlike process of about the same length as the second and fourth joints. The mandibles are of the 

 usual dytiscid form, rather short and stout, and they do not overlap much when closed. The maxilla 

 is similar to that of Thermonectes and consists of a long curved basal portion with a single row of spines 

 on its dorsal surface, a fringe of long hairs along its outer margin, another fringe of short hairs along its 

 inner margin, and a slender, acute spine at the distM end. The palp is four-jointed, the first, second, and 

 fourth joints about the same length, the third joint spherical and much like the similar ones in the 

 antennae. The labium is elongate; the palpiger is one-half longer than wide and rounded at the distal 

 end. Its dorsal surface along the lateral margins and across the distal end is raised somewhat and thickly 

 set with small spines. Each palp is composed of two slender joints, of about the same length and 

 together reaching the tip of the maxilla. The terminal joint is sparsely armed with small spines; the 

 ligula is slender, as long as the basal joint of the palps, and sparsely armed with spines. 



The prothorax is twice as long as wide, the posterior margin where it is widest being twice the width 

 of the anterior, the sides concave. The mesothorax and metathorax are one-half wider than long; the 

 abdominal segments increase regularly in length backwards, the first three increase slightly in width, the 

 fourth is the same width as the third, and the remaining segments decrease rapidly. At the posterior 

 end of the body are two slender cerci, one-third as long as the last segment. 



Habits of the adult. — This beetle is an excellent swimmer, being surpassed in this respect only by 

 Cybister and Dytiscus, and in its jumping ability it comes very close to Thermonectes and Laccophilus, 

 but it is a very poor walker and flounders along awkwardly. In the ponds it is active and restless, 

 moving about almost continuously and scarcely pausing except now and then to eat its prey. It feeds 

 upon dragonfly and damselfly nymphs, the nymphs of Belostoma and Notonecta, mayfly larvae, and 

 the larvae of hydrophilid beetles. It did not attack any of the dytiscid larvae in the ponds, possibly 

 because they are difficult to catch. 



