XIII CONTRIVANCES OF AQUATIC INSECTS 387 



by the transparency of the body, are a few of the arts 

 practised by aquatic Insects, either in self-defence or 

 as a means of pouncing unseen upon their prey. 



The egg-laying of aquatic Insects is attended with 

 special difficulties, some of which spring from the fact 

 that the female fly is in general ill- fitted to enter the 

 element in which the earlier stages have to be passed. 

 These fresh difficulties are met by fresh contrivances. 

 The egg-ropes of Chironomus, the egg-raft of the 

 Gnat, the anchoring threads of the eggs of Ephemera, 

 the floating cocoon of Hydrophilus, are adaptations of 

 peculiar interest. Dytiscus, Notonecta, Ranatra, and 

 certain Dragon-flies lay their eggs in incisions made 

 in submerged plants. But even these carefully 

 hidden eggs are searched out by such egg-destroyers 

 as Polynema, which lay in them their own eggs, from 

 which proceed the parasites which will in the end 

 devour their undeveloped host. 



I might go on to enumerate fresh contrivances 

 under such heads as the constructions of aquatic 

 Insects, the emergence of the winged fly, the defences 

 of resting pupae, and so on, but the subject is in- 

 exhaustible, and the heaping-up of examples proves 

 wearisome. In past ages all these would have been 

 cited as fresh proofs of a wisdom and beneficence 

 which we are unable even to comprehend, far less 

 to imitate. And whatever the cool scientific spirit 

 may have done to weaken that interpretation, the 

 beauty and completeness of natural adaptations come 

 upon us at times with overwhelming force. It is 

 with peculiar interest that we observe how physical 

 principles, the discovery of which is among the latest 



