PRESERVING AND STUDYING INSECTS 



357 



completed, it may be temporarily sealed by covering with a glass 

 plate which is firmly pressed in position. The glycerin has many 

 distinct advantages over water, its density 

 holding the more delicate structures in 

 position, and at the same time it has a 

 higher index of refraction. Plates of vari- 

 ous sizes and depths may be easily con- 

 structed to meet different requirements. 



Rearing insects. If one wishes to study 

 the life history of insects, or if desirous of 

 procuring especially fine specimens, by far 

 the best method is to rear them under 

 artificial conditions. In this work an at- 

 tempt must always be made to simulate 

 natural conditions as closely as possible. 

 There is less liability of the larvae being 

 parasitized if they are placed in a breed- 

 ing cage when quite small. Numerous 

 breeding cages have been constructed for 

 the purpose of rearing larvae. Of these, 

 one of the best is shown in Fig. 493. 

 This consists of a frame with a glass door 

 on one side, the other three sides being 

 covered with cheesecloth. If possible, the 

 food plant is placed in a flowerpot inside 

 the breeding cage. If this is impracticable, twigs and branches 

 can be placed in the cage in bottles of water, the top of the bottle 

 being stuffed full of cotton to prevent the lar- 

 vae from drowning. Another simple breed- 

 ing cage for smaller insects is made by 

 placing a lantern globe or lamp chimney, 

 the top of which is covered with a square of 

 cheesecloth, over the food plant (Fig. 494) 

 in a flowerpot. The food material should be 

 changed frequently, so that it may be kept 

 fresh and sufficient. FlG ^ A glmplc aqua _ 



For rearing large quantities of larvae an r i um f or aquatic larvse 

 open tray three by five feet is most convenient. (After Washbum) 



FlG> 



breeding cage 

 (After Banks) 



