WATER BEETLES IN RELATION TO PONDFISH CULTURE. 



311 



head blackens, the dorsal surface of the prothorax shows the two semilunar black spots, and the wings 

 are darkened. 



The antennae stand out at right angles to the body axis; the long maxillary palps extend back beyond 

 the bases of the second legs. The femora of all three pairs of legs are at right angles to the body axis; 

 the tibiae of the first pair are folded tightly against the femora; the tarsi are parallel with the body axis 

 and some distance apart. In the other two pairs of legs the tibiae and tarsi are in line and extend diag- 

 onally backwards to the mid line. At the posterior end of the abdomen are two strong cerci, each armed 

 with a single long moniliform spine. 



The large styli on the dorsal surface of the body are arranged as follows: 10 along the anterior margin 

 of the pronotum, 8 along the posterior margin, 1 on each lateral margin, and a row of 4 across the center, 

 24 in all. Schi0dte (1872) in his figure of a Berosus larva showed 26 pronotal styli, but out of 40 pupae 

 belonging to this and the following species not one showed more than 24 styli. There is also a similar 

 stylus inside the base of each elytron and wing, two on the first abdominal segment, foui' on each suc- 

 ceeding segment to and including the seventh, the lateral ones being near the longitudinal center of the 

 segment instead of on the posterior margin, two much smaller ones on the eighth segment and two tiny 

 setae above the bases of the cerci on the ninth segment. Each stylus has a thickened base that ends in 

 two short teeth and a thread-like terminal portion. The pupa rests a part of the time on these styli with 

 its back downward, but its normal position is the other side up resting upon its cerci and the styli of the 

 head and pronotum, with its body strongly arched. Out of 25 pupae reared to the adult stage 20 remained 

 in the pupal chamber five days, while the other 5 emerged in four days. 



Habits of the adult. — These beetles swim well but rather slowly; on the land they walk with con- 

 siderable agility and can even run, while their powers of flight are indicated by the fact that they are 

 frequently captured in trap lanterns some distance from the water. They were also among the first 

 beetles to appear in the newly filled ponds described on page 237. None of those under observation ate 

 anything but green algae, although they had abundant opportunity to take animal food. This species is 

 found in nearly all the ponds and furnishes excellent fish food, while both the larvae and the adults are 

 too small to injure even the youngest fish. 



Description of the adult. — General outline elongate oval 4 to 5 mm. in length, the narrowed end 

 anterior; very convex; thorax as wide as the base of the elytra. Head black, with a bronzed surface, 

 finely and evenly punctate; eyes grayish-brown; thorax greenish-yellow tending to orange, with a semi- 

 lunar fuscous spot on either side of the mid line; scutellum elongate; elytra greenish-yellow, each with 10 

 distinct longitudinal striae of coarse black punctures and 8 to 11 small, remote, indistinct black spots, 

 those along the center paired, the others single. Ventral surface dull brownish-black, legs, palps, and 

 antennae yellow; bases of the femora brown. 



Antennae clavate, seven-jointed; first joint elongate, semilunar, second and third joints shorter, 

 narrower, and straight, with a long seta on the outer margin of the second joint. Last four joints swollen, 

 increasing in length distally and covered with fine hairs. Mandibles with three rows of large teeth, the 

 outer row with three teeth, the middle row with two, and the inner row with a single tooth. Inside of 

 the latter, along the inner margin, is a row of stout curved spines. Maxillae of typical form, the stipes 

 with coarse hairs along the outer margin; palp three-jointed and clavate. Labial palps also three- 

 jointed and pilose. 



Berosus pantherinus Leconte, Figures 95, 98, 100, 104, 107, 109, 111. 



Berosus pantherinus (Leconte, 1855, p. 364). 



Egg cases. — ^The egg cases of this species are similar to those of the preceding species but are not 

 flattened as much, the case proper is not circular in outline, and the fag is shorter and wider. They 

 contain, however, about the same number of eggs, which require the same length of time to hatch. 



Habits of the larva. — This larva has the same habits as the preceding one and feigns death in the same 

 way, but it is not as sluggish as striatus and does not lie inert for such long periods. It eats nothing but 

 algae. 



Description of the larva. — It is much smaller than striatus, being only 6 mm. long and 2 mm. wide. 

 The body is not tapered as much as in striatus, especially posteriorly; the lateral gills are flattened in- 

 stead of being cylindrical and are relatively much longer and narrower, the posterior pair being fully 

 as long as the entire body. Furthermore, these gills are trailed inertly along the sides of the body in- 



