WATER BEETI^S IN RELATION TO PONDFISH CULTURE. 



315 



Description of the pupa. — ^This pupa is 15 to 16 mm. long and 8 mm. wide through the thorax; it is 

 clear green in color, becoming brown about the head and appendages as it matures. The general form 

 is elongate-obovate, the posterior end bluntly pointed. The dorsal sm-face of the head and prothorax 

 is armed with large curved styli similar to those on the Hydrous pupa. These are arranged as follows: 

 2 above each eye, 3 very long ones at the anterior corners of the pronotum, 3 shorter ones just inside of 

 them on the anterior margin, 3 on each lateral margin, a transverse row of 4 in front of the center, another 

 transverse row of 3 behind the center, and 10 along the posterior margin, making 35 in all on the pronotum. 

 There are two similar styli on the mesothorax and two more on the metathorax, and six on each of the 

 first seven abdominal segments, the lateral ones mounted on small tubercles. The eighth segment has 

 four tubercles on its posterior margin, each armed with a stylus. The ninth segment terminates in two 

 divergent cerci, nearly 3 mm. long and bifid at their tips. The maxillary palps are very long and reach 

 back beyond the bases of the second legs. The wings and elytra are very short and do not reach beyond 

 the fourth abdominal segment. 



Description of the adult. — Length 14 to 16 mm. Male longer than the female, the latter very obtuse 

 posteriorly; dorsal surface black and shining; ventral surface dark reddish-brown and pubescent. 

 Each elytron shows four rows of distinct punctures, the outer row being double. The metastemal 

 spine does not project behind the coxse of the hind legs. 



Genus LACCOBIUS Erichson. 



Laccobius (Erichson, 1832, p. 20). 



> t This is a genus of minute but very active beetles, whose diminutive size is 

 more than offset by their agility both in the water and on the land. The adults 

 are dark-colored and have the habit of burrowing in the mud or debris on the bottom 

 of the pond and remaining there entirely concealed. They are vegetable eaters and 

 are so small they can do no possible harm, but both the adults and the larvae make 

 good fish food. 



Laccobius agilis Randall. Figure 146. 

 Laccobius agilis (Randall, 1838, p. 19). 

 Laccobius agilis (Richmond, 1920, p. 43; pi. 9, figs. 1-11). 



This is one of the rarer species in the Fairport fishponds, but a few larvae and 

 pupae were obtained in addition to the adults. Since figures of the egg case, the 

 newly hatched larva, and the mature larva have been published by Richmond in 

 the paper cited above (1920), that of the pupa is the only one here presented. No 

 egg cases were found in the fishponds, therefore the description is borrowed from 

 Richmond. 



Egg case. — General form nearly spherical, 1.40 to 1.60 mm. in diameter, the fag ^ a hollow filament 

 7 to 10 mm. long; attached to roots or blades of grass at the water's edge, or to stones. Each case contains 

 from 2 to 11 eggs, which hatch in from 7 to 11 days, the larvae breaking through the side of the case. 



Hahits of the larva. — ^These larvae are poor swimmers, and their usual mode of locomotion is by 

 crawling over the vegetation or along the bottom of the pond. They breathe in the usual manner by 

 means of a stigmatic atrium at the posterior end of the abdomen. When breathing, they usually rest 

 upon the leaf or stem of some convenient water plant, thrust the end of the abdomen above the surface 

 of the water, and then open the atrium. The side of the aquarium was also often used for this purpose. 

 Sometimes the larva swims to the surface head upward and, inverting its body, endeavors to thrust the 

 atrium above the water. This proves difficult, and it may try half a dozen times before succeeding, 

 but once in position, the edges of the opened atrium will support the larva, and it hangs from the 

 surface film. These larvae are not cannibals and may be confined together without eating one another. 

 The only things they were observed to eat in the aquarium were a few very small snails. 



Description of the larva. — General form oblong, four times as long as wide. Length 5.8 mm. ; greatest 

 width through second abdominal segment 1.5 mm. Head quadrangular, slightly elevated, often 



* See p. 332. 



