148 PRACTICAL MICROSCOPY. 



the Polyommatus argus, the Lepidocyrtus curvicollis, and 

 Podura plumbea. These scales are shown in Chapter V. 

 The Podura plumbea is a small insect found in damp shady 



places, under stones in 

 cellars, where they may 

 be caught by sprinkling 

 a little oatmeal near 

 their haunts. They are 



F commonly called spring- 



tails ; and in order to 



help the student in finding them, an illustration is given 

 in Fig. 133, and of the Lepisma saccharina in Fig. 134, each 

 magnified about 12 diameters. 



FIG. 134. 



It is very interesting at times to watch the development 

 of insects and the changes they undergo during their cycle 

 of existence ; for this purpose a " vivarium " is necessary, so 

 that while furnishing them with sufficient air they may be 

 prevented from crawling or flying away, and the respired 

 carbonic acid find easy exit. 



The best kind of vivarium is that shown in Fig. 135, and 

 is so simple that an ordinary tinman can construct one for 

 a trifling cost. 



The framework is made of perforated zinc with a bottom 

 of the same material, on which rests an inner circle of zinc but 

 perforated more closely. This is not fastened to the bottom 



