424 PRESERVATION OF INSECTS. 



tliey conld 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, 

 Illigek), 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 men- 

 tioned . the manure which is taken from the farm-yard, and 

 spread upon the soil already cleared for turnips, is after- 

 wards 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 int-o 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 autum- 

 nal season, and there deposit their eggs for future genera- 

 tions in the succeeding years. These eggs are hatched by 

 the heat of the sun, when the manure is laid upon the 

 ground, or by the warmth of the earth when it is ploughed 

 in, and make their first appearance in the shape of a eater- 

 pillar, which may be obsei'ved jumping and crawling on 

 the land. The leaves of vegetables are their choicest food, 

 and in turnip land, though they find nothing else, they find 

 plenty of leaf, and on this they feed to the absolute ruin of 

 the root."-]- But had this writer taken the trouble to con- 

 fine these dung maggots under a gauze cover till they were 

 hatched, he would have found, instead of the halticag, some 

 common two-winged flies, Avhich a simple experiment would 

 have convinced him do not eat green leaves of any kind, 

 being incapable thereof for want of eating-organs ; and our 

 young naturalists who may wish to try this will be enabled 

 to prove to any farmer, who is in fear of diffusing injurious 

 insects by manure, that no insects bred in dung ever touch 

 a green leaf. 



This remark brings us directly back to our subject of 

 instructing the student how to keep such insects as he may 



* Beechey's Voyage in the ' Blossom.' 

 t Treatise on Agricultiu-e. 



