COMMON OBJECTS WORTH EXAMINING. 297 



2. Elytra.— The hard wing-covers {Elytra) of beet- 

 les are often of startling beauty when examined with a 

 strong light as opaque objects. They are not trans- 

 parent, and cannot be made so, consequently only the 

 surface may be viewed. They are to be examined and 

 mounted dry. 



3. Insects' Feet vary greatly in appearance and in 

 structure. They afford an endless supply of the most 

 interesting objects. They should be cut off with 

 sharp scissors, so as to include part of the leg, and ex- 

 amined in water. If the air clings to the bristles on 

 the leg, dip the latter into a drop of alcohol and trans- 

 fer it to the water on the slide before the alcohol has 

 entirely evaporated. . The feet of the two or three 

 kinds of flies that frequent our houses, the feet of 

 spiders and those of caterpillars, should not be over- 

 looked by the reader. Spiders can be obtained at all 

 seasons, even in the winter, by searching the dark 

 corners of the cellar where the furnace is. 



4. Eyes of Insects should be viewed as opaque ob- 

 jects, unless the student is sufficiently expert to be 

 able to remove the pigment matter and so make them 

 transparent. This can be done with moderate ease in 

 the large compound eyes of the house-fly, but with 

 most other insects it is a delicate operation. The 

 eyes are removed with sharp scissors, soaked in a 

 solution of caustic potash, and the pigment washed 

 from the inside, if necessary, with a fine wet camel's- 

 hair brush. The work is best done under water, and 

 the cleaned eye may then be examined in water. 



The compound eyes of insects like the house-fly are 

 usually so large and convex that only a small part of 

 the surface can be brought into focus at the same time; 



