PISCICULTURE. 349 



dies, protecting the eggs with her dried body. The 

 ordinary cochineal lives in Mexico, on the leaves of a 

 cactus called nopal, and is largely cultivated. Little 

 nests containing the females ready to lay eggs are sus- 

 pended on the spines of the nopal, and the larvae soon 

 appear on the leaves and spread over the plant. The 

 males have wings, but the females are apterous, and 

 remain on the plant, from which they are collected, 

 killed by heat, and dried in the sun. They contain the 

 coloring matter called carmine. 



Lac, which is ordinarily known as shell-lac, is a resin 

 produced on certain varieties of fig-trees in Asia by a 

 species of hemiptera, called the coccus lacca. 



PISCICULTURE. 



Since we have from time to time spoken of useful 

 animals, we should not pass in silence the efforts that 

 have been made to preserve certain species and to enable 

 them to multiply. Fish, in particular, are important 

 from an alimentary point of view ; the entire population 

 of certain towns consists of fishermen, and it is not as- 

 tonishing that the art of breeding and protecting fish, 

 called pisciculture, has been practised from very remote 

 epochs. It was known to the Chinese and to the 

 ancients, has long been carried on in Europe, and is 

 now successfully conducted on a large scale in the 

 United States. There is no difficulty in understanding 

 the interest that attaches to the preservation in our 

 lakes and watercourses of useful species, such as the 

 carp, perch, bass, trout, and salmon. Artificial hatcher- 

 ies have been invented, and the habits of the fish have 

 been closely studied; for, in order to ascertain the best 

 conditions for reproduction, we must know how and in 



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