33° 



BAKER : HYDROBIUS FUSCIPES. 



woven threads, and is about 4 mm. by 3 mm., flattened and 



rounded at one end. The other end, the last one finished, 



terminates in an irregularly shaped flap, by which the cocoon is 



fastened to the blades of grass, etc. Sometimes this loose flap is an 



inch and a quarter in length, and often as many as th'ree cocoons 



are attached to one blade of grass. Each beetle makes three or four 



cocoons, at intervals of about a fortnight. In a 



few days the larvae (Fig. 4) emerge from the eggs, 



and biting through the top of the cocoon, which is 



thinner than the sides, climb on to the exposed 



portions of water-plants, and after resting there a 



short time enter the water, and suspending them- \f^ 



selves by their peculiar anal processes to the 



surface film of the water, gyrate about after the |fT 



style of a Chironomus, only always keeping the 



anal segment, with the spiracular openings, above 



the surface of the water. This anal segment is 



very flexible, and they can crawl sideways, 



horizontally, or vertically, without altering the 



exposed tip. These motions are evidently for 



the purpose of securing the small animals upon 



which they, at this early stage, feed. When not 



engaged in performing these ' figures of eight,' they 



lest upon the blades of grass or leaves of plants 



which lie upon the surface of the water. At this 



stage they are very transparent, and the internal p. ^ 



organs, including their respiratory and circulatory Larva. x6. 



systems, can be easily traced. As they grow older they get opaque, 



owmg to the accumulation of fat. The larva, being hea\ier than 



water, quickly drowns, if by any accident it is entirely submerged, 



and there are no means by which it can crawl out. When first 



hatched its head is much wider than its body, but whereas the 



former grows but little, the latter soon begins to assume more equal 



proportions, and at the end of a week, at which time the diameter of 



the head and the body are about equal, they measure about 4!- mm. 



in length. After this, though their heads grow very little, their 



bodies increase both in width and length, until after about three 



months spent in the larval state, they attain a total length of about 



12 mm., and are ready to pupate. They have at all times a most 



voracious appetite, and, if food is at all scarce, show very strong 



cannibalistic propensities, and frequently, after placing as many as 



a dozen together in one tank, have I found at the end of about 



a fortnight only one or two fine, well-fed ones and fragments of the 



Nov. 1894. 



