260 INSECT WATER TRESPASSERS. 



first I could hardly believe my eyes; but having found 

 several specimens and shown them to some of my 

 friends, there can be no doubt about the fact. More- 

 over, the same insect was again observed, within a 

 week, by another entomologist, Mr. Duchess, of Step- 

 ney. This gentleman mentioned it to Dr. Sclater, and 

 from his description and sketch, there can be no doubt 

 that the insect observed by him belongs to the same 

 species. 



"It is a very curious coincidence that, after re- 

 maining so long unnoticed, this little insect should 

 thus be found, almost simultaneously, by two indepen- 

 dent observers. Perhaps this may, in part, at least, be 

 accounted for by supposing that the insect was un- 

 usually abundant this summer. Yet Mr. Duchess ap- 

 pears to have met with only one specimen. Mine were 

 altogether twenty-one in number, and the females 

 were more than twice as numerous as the males. 



' ' As the motion in Polynema natans is caused by the 

 wings, it might almost be called a flight; owing, how- 

 ever, to the density of the medium, and partly, 

 perhaps, to the direction in which the wings act, 

 the movement, though not inelegant, is slow, and 

 is rather a succession of jerks than a continuous pro- 

 gression. 



" The insect is provided with tracheae, and respi- 

 ration appears to take place through spiracles in the 

 usual manner. Most of those insect larvae which 

 spend much of their time under water are either pro- 

 vided with gills, or carry down with them a supply of 

 air attached to their body, and from which the tracheae 

 can be replenished. Our insect possesses neither of 



