PRESERVATION OF INSECTS. 361 



observation of these forms a most interesting branch 

 of the study. The species which prey on animal 

 substances, either living or dead, often possess such 

 habits as may deter some students from attending to 

 them, and yet they fulfil most important purposes in 

 nature, and have furnished the distinguished natu- 

 ralists, Redi, Swammerdam, Leeuwenhoeck, Reau- 

 mur, and De Geer, with highly interesting subjects 

 of research. The history of many of these animals 

 becomes highly interesting, from its relation to our 

 domestic comfort. The house-fly, for instance, is 

 said to breed amongst horse-dung ; but that its 

 maggots find food in other substances not hitherto 

 ascertained, is rendered probable by the enormous 

 numbers which are sometimes seen at a distance 

 from places where they could obtain the alleged 

 nutriment, as in Pitcairn's island in the Pacific 

 Ocean*, where there never was a horse. With 

 reference to husbandry, again, the correct history of 

 many insects is perhaps still more important, of 

 which we beg leave to give one striking instance 

 in the case of what is called the turnip-fly (Haltica 

 Nemorum, ILLIGER), which is not a fly, but a small 

 jumping-beetle. " In these circumstances," says 

 Mr. W. Greaves, " I flatter myself will be found the 

 cause of the disease here mentioned: the manure 

 which is taken from the farm-yard, and spread upon 

 the soil already cleared for turnips, is afterwards 

 turned in with the plough ; the seed is then put in, 

 and nature does not rest till it is time for hoeing. 

 Now, it must be obvious that manure put into the 

 ground at this season of the year (June) must be 

 full of eggs of flies, which are seen to swarm upon 

 manure heaps in the autumnal season, and there de- 

 posit their eggs for future generations in the succeed- 

 ing years. These eggs are hatched by the heat of 

 * Beechey's Voyage in the Blossom. 



