BEARING LEPIDOPTERA 113 



When ova are kept in a warm room, very great inconvenience 

 and even loss is sometimes caused by the appearance of larvae before 

 the necessary food plant shows its buds. Yet, on the other hand, 

 it is sometimes a great gain to the entomologist to get certain 

 broods off early in the season, providing the food is at hand ; for 

 in this way he can not only get some of his work over during a 

 slack season, but also, if he desires it, secure an additional brood ; 

 that is, one brood more than the usual number. Thus, supposing 

 a certain species he is rearing is naturally double-brooded, he can, 

 by judicious management, secure three successive broods before the 

 food plant casts its last leaves. 



This hastening of the natural events of insect life is known as 

 forcing, and merely consists in subjecting the species concerned to 

 a reasonable amount of artificial heat, such as that of a room in 

 which a fire is always kept, or of a hothouse. 



It is interesting at all times to note the dates on which eggs are 

 laid or collected, and the times at which the 3 T oung larvae appear. 

 In addition to this all changes that take place in the colours or 

 forms of eggs should be carefully observed ; for such changes will 

 assist you in distinguishing between fertile and sterile ova, and 

 also enable you to judge approximately as to the date of the 

 appearance of future broods. 



Rearing Larvce 



The main point in connection with the rearing of larvae is cer- 

 tainly the selection and construction of the cages or their substitutes. 

 For newly hatched and all very small caterpillars a small bottle 

 with a wide mouth makes a very fair abode. Put a layer of sand 

 or sifted soil in the bottom, fix in this a small twig of the food plant 

 or lay a few leaves on the top, and then, after the larvae have been 

 introduced, cover the top with a piece of muslin, held in place by an 

 elastic band. 



The great drawback with this arrangement is the lack of any 

 provision for keeping the food moist and fresh, thus rendering a 

 change necessary at very frequent intervals ; but this may be 

 obviated by using damp sand as a foundation for the little twig 

 of food plant. With this improvement, if you cover the top of the 

 bottle with apiece of glass, a saucer, or any impermeable substance, 

 you may keep the twig fresh for several days, generally until the 

 disappearance of the last leaf calls for a fresh supply ; but it is 



