NYMPHS OF WATER-MOTHS, 279 



after which he flew away with it^, undisturbed by the 

 wind. 



The same author says^ that the nymphse of the 

 water-moths of our rivers, which cover themselves 

 with cases of straw, gravel, and shell, contrive to make 

 their habitations nearly in equilibrium with the water. 

 When too heavy, they enlarge their bulk with a bit 

 of wood or straw ; when too light, they add a bit of 

 gravel. The instinctive faculty teaches them, without 

 reasoning, to adjust the weight of their frail dwelling 

 with that of an equal bulk of water. The case of the 

 wasp and the fly seems less consistent with the unifor- 

 mity of the operations of those insects. 



Insects, in some instances, mistake their instincts. 

 At a certain season of the year, the fire-flies in Ja- 

 maica are seen in the evenings in great abundance. 

 When they settle on the ground, the bull-frog greedily 

 devours them ; which has probably suggested the idea 

 of destroying those animals by throwing red-hot pieces 

 of charcoal towards them in the dusk, when they leap 

 at them, and hastily swallowing them, are destroyed. 

 In like manner, the putrid smell of the stapelia, or 

 carrion- flower, allures the large flesh-fly to deposit her 

 eggs in its beautiful petals, where the young wonns, 

 when hatched, perish for want of nourishment. 



Long-legs, moths, and many kinds of flies, mistake 

 the light of a candle for the rays of the sun, and rush 

 into the flame to their destruction. 



