PRESERVING WATER ANIMALS 



almost altogether by entomologists. Insects dropped into 

 either of these bottles soon die from the fumes. It is general- 

 ly advisable to secure cyanide bottles from dealers rather 

 than to prepare them at home since potassium cyanide is a 



Fig. 28. — I, Killing bottle for insects; 2, air-net; 

 3, wire sieve-net for pulling up mud and trash. 



deadly poison and should be handled with extreme caution. 

 They should always be kept tightly stoppered in order to 

 conserve their deadly fumes for the insects. A few drops of 

 carbona or carbon tetrachloride sprinkled on cotton and put 

 into a tight bottle will kill insects satisfactorily and yet may 

 be safely handled. It usually has to be renewed at each 

 collecting trip but carbona bottles can be made in such a 

 way that they will last much longer. Soak some pieces of 

 old rubber overshoe or inner tube in carbona; put these in a 

 bottle with absorbent cotton packed around them and a 

 piece of cardboard to hold them all down. 



29 



