WATEE-BEETLES. 217 



In captivity these beetles, which are not great eaters, may be 

 fed upon pieces of raw meat, water- and garden-worms, or 

 house-flies killed and placed upon the water. While watching 

 the quick and intricate movements of the " Whirligigs " upon 

 the water, one wonders how they are always able to avoid 

 colliding; and they travel with such rapidity that it is 

 difficult to follow them with the eye and see how they steer 

 themselves. Mr. H. W. Bates, writing in Cassell's " Natural 

 History," while speaking of their gyrations, says : " The two 

 hinder pairs of legs are extremely short, broad, compressed — 

 modified, in fact — ^to suit their extraordinary mode of locomo- 

 tion — a rapid skimming in curves or circles over the surface 

 of the water. The rapid forward motion is produced by the 

 quick fore and aft movement of these strong and well-knit 

 members, and the curves by the long anterior legs, which, 

 usually kept folded under the breast, are jerked out one at a 

 time, so as to change the straight line of progression into 

 a curve." The G-yilnidse lay their cylindrical eggs (which 

 hatch in about a week) end to end upon water-plants. The 

 larvae look somewhat like aquatic centipedes, owing to the 

 filamentary appendages which are fixed to the abdominal 

 segments of then- bodies. These appendages are hoUow, and 

 are used for respiration. When the larvae axe ready to 

 assume the pupal state, they ascend the stalk of some aquatic 

 plant, and then, above the surface of the water, spin a 

 cocoon, from which they emerge in about a month perfect 

 " Whirligigs." These lai-vae, 

 which seem to be rather 

 hardier than those of other j^ 



aquatic beetles, can easily be •^^. 



kept in confinement. Small 

 aquatic animal Ufe, water- 

 worms, and the fry of mol- 

 luscs, form their best food. fig. 138. Gvrincs nataior. 



Gyrinus nataior (Fig. 138), 

 which is about the commonest 



of the Gyrini, is ovate and convex in shape, and very glossy 

 bluish-black in colour. The edges of its elytra, which are 



