1920] Richmond, Studies on the Biology of the Aquatic Hydrophilidoe 47 



side a little anterior. Mesonotum and metanotum with a pair of transverse styli. 

 Inner spur of metatibia fairly prominent. All tarsi ending in a spine and all tibiae 

 spinous on the outer side. First to seventh tergites with a transverse row of four 

 subequal styli: the outer one on each side arising from prominent tubercles; second 

 to seventh pleurites each with a stylus; eighth segment has two, small, cereal-like 

 lobes, projecting dorsally. Ninth segment has a pair of cerci, which are about four 

 times as long as the latter lobes and project backwards, diverging about 45°. The 

 externo-caudal angles of the ninth segment are prominent and acute. The spiracles 

 are exposed and well defined. 



Berosus Leach 



Schiodte gave the complete life history of B. spinosus and later the 

 larval differences of B. signaticoUis. Brocher described the egg-case 

 and young larva of B. cericeps ( = signaticoUis) and, although he did not 

 rear it, considered that it could be no other species because of its size. 



At least two species, B. peregrinus and B. striatus, occur in the 

 vicinity of Cayuga Lake and doubtless others would be found if more 

 time could be devoted to their study. These two are fairly distinct; 

 the latter is separated from the former by its usually larger size and by 

 the two small teeth, instead of only one, at the middle of the notch of the 

 fifth abdominal sternite. The carination of the abdominal sternites of 

 the male peregrinus, often used as a character of separation, seems to be 

 quite variable in the specimens examined. 



The beetles may be taken from early spring until late fall but are 

 most frequent in May and late August. They are hardly ever taken in 

 swift waters but inhabit small pools with an abundance of moneywort, 

 Chora. Elodea, cut -grass, alga, etc. The fact that they are good swimmers 

 requires the use of nets, in contrast to hand collecting so profitable for 

 most of the other genera. The net must be drawn through the water 

 rapidly for, as soon as disturbed, the beetles quickly dodge down to the 

 bottom of the pool and in a moment are buried in the mud. At times 

 many specimens may be gathered by pulling the vegetation out of the 

 water quickly and looking it over carefully. They do not easily escape 

 when thus taken, as they are very clumsy when out of water. 



In the aquarium, they were observed feeding on the decaying leaves 

 of moneywort, attacking both the upper and under side and eating holes 

 entirely through. While watching them feeding, a peculiar, almost 

 incessant action was noted. The beetles, holding on to the plants with 

 their two anterior pairs of legs, kept sweeping the swimming hairs, which 

 fringe the tarsi and tibiae of the hind legs, down and forward across the 

 film of air covering the abdomen. Just what the function of such a 



