436 COLEOPTERA. 



if in autumn hibernates as a pupa, to transform to a beetle in 

 the spring. 



In Haliplus the antennae are ten-jointed, bristle-shaped, and 

 the legs are scarcely adapted for swimming, being narrow. 

 The body is very convex, spotted with black or gray, while 

 the elytra are covered with rows of punctures. In the remain- 

 ing genera, the types of the family, the antennae are eleven- 

 jointed and the hind legs oar-like. "The larvae differ not only 

 by their dorsal segments being armed with spines, which gives 

 them a very grotesque appearance, but by their possessing only 

 one claw, and by their anal segment (which is rudimentary 

 in all other Dytiscidse) being enormously elongated and forked, 

 so that the anus is placed on the under side of this pe- 

 culiar tail, and the spiracles of the eighth pair, which are ter- 

 minal and tube-like in other Dytiscidce here become lateral 

 and quite plain." (Schiodte.) In Colymbetes and Agabus the 

 anterior tarsi of the males are broad, oblong, and covered be- 

 neath with cups of equal, or nearly equal, size. Agabus differs 

 in having the thorax as wide at the base as at the middle, or 

 still wider. In Dytiscus the ovate, not very convex body is 

 usually broader behind the middle, and the last joint of the 

 palpi is not elongated, while in Acilius which is usually 

 banded, the intermediate tarsi of the male are not dilated. 

 The females of these two genera often have the elytra deeply 

 furrowed, while those of the males are smooth. Dytiscus 

 fasciventris Say and Acilius mediatus Say are common in all 

 our ponds northward. 



GYRINID^E Latreille. Whirligigs. These oval bluish black 

 beetles are easily distinguished by their peculiar form and 

 habits. They are always seen in groups, gyrating and circling 

 about on the surface of pools, and when caught, give out a 

 disagreeable milky fluid. Like the previous family, upon being 

 disturbed, they suddenly dive to the bottom, holding on by 

 their claws to submerged objects. They carry down a bubble 

 of air on the tip of the abdomen, and when the supply is ex- 

 hausted rise for more. 



The cylindrical eggs are placed by the female, end to end, 

 in parallel rows on the leaves of aquatic plants, and the larvae 



