356 



ELEMENTARY ENTOMOLOGY 



This sort of dissecting tray works very well for rough dissection, 

 where nothing more than a hand lens is required. It has the 

 objection, however, of the projecting sides, which frequently pre- 

 vent one from manipulating the dissecting instruments as desired. 

 By far the most successful dissecting tray for insect work that we 

 have used is made as follows : A glass plate four by five inches is 

 thoroughly washed in alcohol in order to remove all traces of dirt. 

 This is then placed in a shallow pan which has been previously 

 coated with vaseline or oil. A mixture of four parts paraffin and 



one part beeswax is next 

 poured over the glass 

 plate to a depth of about 

 one inch. After this is 

 thoroughly cool, it is re- 

 moved from the pan and 

 the paraffin trimmed off 

 to the edge of the glass 

 plate. A trough is scraped 

 out in the center of the 

 plate to accommodate the 

 body of the insect to be 

 dissected. After a little 

 experience one can very 

 quickly regulate the size 

 and shape of this trough 

 to the best advantage. A 

 sufficient amount of par- 

 affin should be left be- 

 neath the insect to permit 

 of its being firmly pinned 

 in position. The work 



FIG. 493. The Riley breeding cage 



will also be greatly facilitated if glycerin, to which an excess of 

 chloral hydrate has been added, is used as a dissecting medium in 

 place of water. This form of tray has a number of distinct advan- 

 tages. In the first place, the work can be carried on entirely with 

 the dissecting microscope, or even a low power of the compound 

 microscope. There are no projecting sides to interfere with the 

 manipulation of the instruments, and if the dissection is not 



