INSECT A. 



The larvae too are an interesting study ; this stage in the 

 gnat, dayfly, and even of the Dytiscus, Fig. 132, will amply 

 repay the observer for the attention he bestows upon it. 



FIG. 130. FIG. 131. 



When required for immediate examination, no special 

 care is requisite; but if for dissection and permanent 

 mounting afterwards, they should 

 be immersed in a mixture of 

 equal parts of glycerine and 

 water, dilute acetic acid, or even 

 dilute alcohol (for some things 

 which require hardening), in 

 order to ensure preservation. It 

 must be understood, however, 

 that this is not universally ap- 

 plicable. There are some objects 

 which would be spoiled by im- 

 mersion in a fluid, and these, of 

 course, must be prepared while 

 in the fresh state. FlG - I32< 



The scales of several insects are much used as test objects, 

 notably those of the Lepisma saccharina, Morpho menelaus, 



L 2 



