WATER BEETLES IN RELATION TO PONDFISH CULTURE. 



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14. Smaller, 17 mm. long or less; anterior margin of pronotum smooth; cerci crooked, tapering, 



sparsely setose Colymbetes. 



15. Body densely covered with setae; cerci also setose; metatibial spine short and hardly discernible. 



Hydroporus. 



15. Body with few setae; cerci naked; metatibial spine long and very prominent; five supraorbital 

 styli above each eye Coptotomus. 



Genus PELTODYTES Regimbart. 



Peltodytes (Regimbart, 1878, p. 450). 

 Cnemidotus (Erichson, 1832, p. 48). 



A genus of small beetles, both the larv83 and adults of which feed exclusively 

 upon algae. They are yellowish or reddish with black spots on the elytra, which 

 vary in number, size, and arrangement in the different species. They may be 

 distinguished from the other haliplids by the terminal joint of the labial palps, 

 which is longer than any of the preceding joints, and by the coxae of the hind legs, 

 which cover all but the last segment of the abdomen. The genus is represented 

 in the Fairport fishponds by a single species. 



Peltodytes edentulus (Leconte). Figures 8 and 9. 

 Cnemidotus edentulus (Leconte, 1863, p. 21). 



Peltodytes edentulus (Matheson, 1912, pp. 174 and 186; fig. B, text; pi. 10, figs. 2, 5, 6, 9; pL 13, figs. 20, 21, 23, 25-27, 29-31; 



pi. 14, figs. 33-35). 

 Peltodytes edentulus (Roberts, 1913, p. 122). 



The eggs. — The eggs are fastened individually to filaments of Nitella or Chara. The average time 

 required for hatching is about two weeks. 



Habits of the larva. — ^The natural history of the Haliplidse has been admirably worked out by 

 Robert Matheson and was published in 1912. The complete life history of the above species was also 

 secured by the writer, and it confirms the statements published by Matheson, except in regard to 

 the duration of the prepupal and pupal periods. This larva can only crawl about slowly over the 

 algae, trailing its long spines. It can not run or swim at all, but it is a most persistent crawler and, when 

 hunting for a place to pupate, travels a longer distance from the water's edge than any other larva studied, 

 except that of the gyrinid (Dineutes americanus) . 



It is the only larva that constantly refused to pupate in an artificial mud cell. It always persisted 

 in crawling out and making its own pupal chamber somewhere else. In spite of its porcupine coat 

 of bristles it can burrow readily into mud considerably hardened. It feeds entirely upon filamentous 

 algae, such as Spirogyra and Mougeotia, and the structure of its mouth parts and legs is peculiarly 

 adapted to this sort of food. It breathes through tracheoles in the long jointed spines, and thus has 

 no need to come to the surface for air. It has no visible spiracles. 



Description of the larva. — General form an elongated cone 6 mm. in length, the thorax and the first 

 four abdomen segments about the same diameter, the last five abdomen segments tapered to a blunt point. 

 The head is considerably narrower than the thorax, somewhat depressed, turned downward almost at 

 right angles to the thorax, and tapered anteriorly. The prothorax is armed with six dorsal jointed spines, 

 nearly as long as the body. Four of these are close to the anterior margin, two lateral and two dorsal, and 

 have enlarged ba-ses; the other two are dorsal and farther back. The meso and meta thorax and the first 

 seven abdomen segments each have a transverse row of four spines, two lateral and two dorsal. The 

 last two abdomen segments have only two dorsal spines apiece, each 4.5 mm. in length, and no lateral 

 ones. 



The number of joints in these spines varies from 11 in the posterior dorsal pair of the prothorax to 

 about 18 in the meso and meta thorax. The basal joint is rather long, the next two or three are very 

 short, and the remainder are of varying lengths. These 46 spines give the larva very much the appearance 

 of a porcupine with abnormally developed quills (fig. 8). 



The antennae are four-jointed with a terminal spine, the last segment consisting of two fused pieces 

 placed side by side. The mandibles are short and wide with rounded ends; the sharp tip is on the inner 



