120 INSECT TRANSFORMATIONS. 



In the practical manag'ementoftheeg^p^s of the silk- 

 worm Count Dandolo directs the temperature of the 

 stove-room to be 64° when they are first put in. 

 " The third day the temperature should be raised to 

 66® ; the fourth day to 68° ; the fifth day to 71° ; the 

 sixth day to 73^; the seventh day to 75°; the 

 eighth day to 77° ; the ninth day to 80°; the tenth, 

 eleventh, and twelfth days to 82°. When the tempe- 

 rature of the stove-room is raised to 75°, it is advan- 

 tageous to have two dishes, in which water may be 

 poured, so as to offer a surface of nearly four inches 

 diameter. In four days there will have taken place 

 an evaporation of nearly twelve ounces of water; the 

 vapour, which rises very slowly, moderates the dry- 

 ness which might occur in the stove- house, particu- 

 larly during a northerly wind : very dry air is not 

 favourable to the development of the silk-worm*." 

 Damp ov stagnant aic, or sudden changes of tempera- 

 ture, either high or low, are exceedingly injurious to 

 the hatching of eggs. 



From some very curious experiments of Miche- 

 lotti, it appears that exposure to light is by no means 

 favourable to the hatching of eggs. This ingenious 

 naturalist inclosed a number of eggs in glass vessels, 

 admitting the light to one series and excluding it 

 from another, similar in every other particular. The 

 result was, that few or none of the eggs exposed to 

 light were hatched, while those in the dark were 

 almost all fertile. He arrived at the same results in 

 his experiments upon vegetable seeds t- Kirby and 

 Spence justly remark that these curious facts may 

 account for so many insects fastening their eggs to the 

 under sides of leaves, and may be the final cause of 

 the opaque horny texture of those exposed in full day |. 



Among the singular circumstances in which insects 

 dilfer from the larger animals, we may reckon that 



* Count Dandolo on Silk-Worms, Eng. trans., p. 55. 

 I Philosophical Mag. vol. ix. p. 244. J Introduc. iii. p. 77, 



