328 INSECT LIFE. 



ties or cans which are filled with sand saturated with 

 water. By keeping the sand wet the plants can be 

 kept fresh longer than in water alone, and the dan- 

 ger of the larvae being drowned is avoided by the 

 use of sand. 



Many larvae when full-grown enter the ground to 

 pass the pupa state ; on this account a layer of loose 

 soil should be kept in the bottom of a breeding cage. 

 This soil should not be allowed to become dry, 

 neither should it be soaked with water. If the soil 

 is too dry the pupae will not mature, or if they do so 

 the wings will not expand fully ; if the soil is too 

 damp the pupae are liable to be drowned or to be 

 killed by mold. 



It is often necessary to keep pupae over winter, 

 for a large proportion of insects pass the winter in 

 the pupa state. Hibernating pupae may be left in 

 the breeding cages or removed and packed in moss 

 in small boxes. Great care should be taken to keep 

 moist the soil in the breeding cages, or the moss if 

 that be used. The cages or boxes containing the 

 pupae should be stored in a cool cellar, or in an un- 

 heated room, or in a large box placed out of doors 

 where the sun can not strike it. Low temperature 

 is not so much to be feared as great and frequent 

 changes of temperature. 



Hibernating pupae can be kept in a warm room if 

 care be taken to keep them moist, but under such 

 treatment the mature insects are apt to emerge in 

 midwinter. 



An excellent breeding cage is represented by Fig. 

 288. It is made by combining a flower-pot and a 

 lantern-globe. When practicable, the food plant of 



