[il-'J POND CULTURE. ,-35 



tables, kitcbeu refuse, dead animals, yeast, &c. Tlic whole is covered 

 with a thiu layer of straw cut fine and some earth, and the pits are in 

 rainy weather covered with boards. 



All through the summer, but especially on warm, sunny days, a large 

 nuuiber of flies of the species Sarcophaga, Musca, Stomosis, and other's, 

 attracted by the odor of the decaying matter, visit these pits to deposit 

 their eggs, from which are developed quickly-growing larvie, which, ac- 

 cording to the state of the weather, may reach their full dcNelopnient 

 in eight to fourteen days. After that period they change to tube- 

 shaped cocoons, from which, after fourteen days, flies emerge to engage 

 immediately in the propagation of their species. The gigantic scafc on 

 which these flies increase may be judged from the fact that the females 

 of some species lay as many as 200,000 eggs, which, in about twenty-four 

 hours, are transformed into maggots, the entire transformation from 

 the egg to the fully-developed insect occupying only twenty-nine days. 

 Only those larvae which are developed late in autumn live through the 

 winter as cocoons. The maggot-pit will also produce eggs, larva;, and 

 cocoons of other insects. The maggots, with the rest of the contents of 

 the pit, are dug up with spades and thrown into the water. Such pits 

 should be far from human habitations, and at some little distance from 

 the ponds, on account of their nauseous and unhealthy effluvia.* 



Before closing this chapter on the feeding of the carp I would strongly 

 recommend to make experiments in feeding, and give my views as 

 to the manner in which this should be done. Unfortunately, I had to 

 give up pond culture before I was enabled to carry out this idea which 

 I had cherished for a long time. The difficulty in these experiments is 

 caused mainly by the circumstance that carp cannot be kept in a 

 stable like horses or cattle, and that consequently they cannot be 

 prevented from taking other food than that which is given to them. 

 Experiments made in tanks of w-ood or stone, filled with pure water, 

 would, on the other hand, lead to erroneous results, as the increase of 

 growth gained by using a certain article of food would be neutralized 

 by the stay in cold water and by other unnatural conditions. At the 

 time when I conceived the idea of making such experiments, Mr. Ho 

 rak was kind enough to write to me and suggest various ways of meet- 

 ing the principal difficulties. He says : " It will be best to make com- 

 parative experiments, viz., to construct G to 10 ponds of the same size, 

 all having the same soil, and stocked with the same number of fisL. 

 Each of these ponds should be supplied with a different kind of food, 

 and the result shoiTld be carefully noted. One pond should be left 

 to nature, and no' artificial food should be introduced into it. Each 

 pond should have its separate ditches for supplying and carrying off the 

 water. The results of the fisheries would be the results of the different 

 methods of feeding." To this I would add that it will be advisable to 

 choose for these ponds a soil containing as little fish-food as possible. 



*Balclanius, Bandhuch der FediTviehzucht. 



