Vol. XXV'ii] ENTOMOLOGICAL NEWS. 31! 



A New Killing Bottle. 



By WM. MOORE, Asst. Prof, of Entomology, University Farm, 

 University of Minnesota. 



In Bulletin No. 167 of the United States Department of 

 Agriculture, mention is made of the feasibility of using para- 

 clichlorobenzene as a substitute for potassium cyanide in kill- 

 ing bottles. Being interested in the benzene derivatives and 

 having a number on hand, killing bottles made of various 

 derivatives of benzene were tried out. They all proved of 

 value, but paradichlorobenzene being a solid gave the best 

 results. 



By placing a few pieces of paradichlorobenzene in the bot- 

 tom of the desired bottle and heating to 55 deg. C. either over 

 a flame or by dipping in hot water the paradichlorobenzene is 

 melted. The bottle, without being corked, is then carefully 

 placed in a cool place or in cold water until the paradichloro- 

 benzene has solidified. Crystals are often found on the sides 

 if the cooling is rapid, but these can easily be removed with 

 a cloth. 



The advantages of a paradichlorobenzene killing bottle over 

 potassium cyanide are: First, the ease with which it can be 

 made ; second, the fact that paradichlorobenzene will not ab- 

 sorb water and thus spoil the bottle and specimens; third, the 

 paradichlorobenzene bottle is full strength as soon as made 

 and remains full strength as long as there is any of the mate- 

 rial in the bottle ; fourth, the bottle can be easily remade by 

 putting in fresh paradichlorobenzene and melting, rfifth, 

 paradichlorobenzene is not very poisonous to higher animals 

 and great care does not have to be taken to clean up all the 

 small pieces if a bottle is broken. This is of particular value 

 where the bottles are used by students. 



The disadvantage is the fact that if the bottle becomes warm 

 and is then cooled that crystals are apt to be formed on the 

 sides of the bottle or even on the specimens. Those on the 

 bottle can easily be removed by a cloth, while the crystals on 

 the specimens will soon evaporate without injury to the speci- 

 men when it is removed to the air. 



