now TO COLLECT AND PRESERVE INSECTS 



11 



The best all-round killing agent for adult insects is cyanide of 

 potassium. It should be broken into pieces varying in size from 

 that of a small pea to that of a hickoiy nut, according to the size of 

 the bottle to be used. Olive bottles make good medium-sized bottles, 

 while fruit jars are bettor for large moths and butterflies. Tubes even 



as small as 34 inch in diameter 

 by about 2 inches long are 

 not too small for some things. 

 Avoid bottles with strongly con- 

 stricted necks. Avoid also 

 bottles made of thin glass. There 

 are many ways of keeping the 

 cyanide in position and 

 the bottle in good condi- 

 tion. The most general way 

 is to pour a thin layer of plaster 

 of Paris over a layer (from 3^-% 

 inch deep) of cyanide. How- 

 ever, since such a bottle will 

 quickly get too moist from the 

 specimens and decomposition 

 of the cyanide, some further 

 device is almost always used. 

 The pieces of cyanide may be 

 wrapped in soft absorbent paper 

 or imbedded in dry sawdust be- 

 fore the plaster is poured on. 

 Another way is to imbed it in dry 

 plaster before pouring on the 

 wet. A piece of blotting paper 

 should be fitted tightly over 

 the plaster after it has ''set." 

 See Fig. 5. Some do not use 

 plaster but imbed the cyanide 

 in cotton and cover this with 

 a piece of blotting paper or a 

 thin porous cork. A dangerous but otherwise fairly satisfactory 

 method is to imbed a piece of cyanide on the inside surface of the 

 cork and have none in the bottle itself. This bottle will be dry but 

 not strong and as the cork will in time become saturated with poison 



Figure 5. Diagram of a cyanide killing bottle. 

 1, Cork; 2, Blotting paper; 3, Plaster of Paris; 

 4, Pieces of cyanide in sawdust. 



