DRYOPIDvE. 



127 



and Erichson described Ancyronyx from CeyloD, the latter genus 

 being allied to the European and North American Meter onyclius. 



The members of the family vary considerably in shape, but are 

 much alike in their habits, being found for the most part in 

 running water, clinging with their strong claws to water-plants or 

 submerged logs or to the undersides of stones. Many of them 

 are strongly pubescent beneath, and some also above, and they are 

 thus able to carry a film of air with them for respiration under 

 water ; they have no power of swimming, although most of their 

 life is aquatic. 



The larvae are found with the perfect insects and are very 

 variable ; those of Dry ops are said to live in damp earth under 

 stones and to resemble the larvae of Elaterid^e. The larvae of 

 Elmis are very different, being elongate-elliptical, but narrowed 

 behind, with the segments extended at each side and furnished 

 laterally with long hairs ; the abdomen ends in a long narrow 

 smooth anal appendage terminated by three sets of filamentous 

 branchiae through which the insects respire. 



The North American genus Psejahenus is placed by some authors 

 in the Dryopid^; and by others is regarded as a separate family. 

 Dr. Horn not long before his death kindly sent me a pamphlet of 

 his from the ' Transactions of the American Entomological Society/ 

 x, 1882, containing notes on some "Little known Genera and Species 

 of Coleoptera," with figures of the upper and under side of this 

 anomalous insect. As he points out, the structure of the legs and 

 antenna is decidedly like that of Elmis, while that of the under- 

 side is very like certain Dascillid^:, and he believes that Psephenus 

 is a genus " with Elmid affinities pointing strongly in the direction 

 of the Eubriid series of Dascillid.e." The larva of the genus is 

 especially abundant in the rapids of Niagara and is peculiar in 

 shape, being entirely elliptical and crustaceiform. According to 

 Leconte and Horn, however, who had plenty of opportunities of 

 seeing it, it differs but little from the larva of Belichus, which they 

 place in their tribe Paeni^i. The position of the Deyopid^ is 

 evidently near the Heteroceridje, and one or two authors (e. g. 

 Lameere, Ann. Soc. Ent. Belg. 1900, p. 363) include the latter 

 family under the former ; they are, however, quite distinct both 

 as regards the perfect insect and the larva. 



I. Abdomen with five visible ventral segments. 



i. Anterior coxae transverse, with distinct tro- 



chantin Dryopin^. 



ii. Anterior coxae globular, without trochantin . . Elminje. 



II. Abdomen with seven visible ventral segments in 



the male and six in the female ; anterior coxae 



with very large trochantin Psephenin2e. 



