Vol. xxvii] ENTOMOLOGICAL NEWS. 311 
A New Killing Bottle. 
By Wo. 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- 
dichlorobenzene 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,—fifth, 
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. 
