2 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. IO3 



I. KILLING 



Since the final results are, in large measure, dependent upon the 

 killing agent used, and the manner in which killing is accomplished, 

 the choice of a suitable lethal chemical and its proper application be- 

 come matters of the highest importance. In general it may be said 

 that killing by means of the vapors from volatile anesthetics (lipoid 

 solvents) is to be preferred to direct submergence in any fluid. Two 

 such substances are recommended: 



a. Carbon tetrachloride. — If specimens do not come into direct 

 contact with the fluid, they will remain relaxed after death, especially 

 if the catch is large and is allowed to remain in the killing bottle at 

 least 24 hours. A full bottle, however, should not be neglected longer, 

 as disintegration of soft parts will soon set in with consequent loss 

 of setae and abdominal segments. A convenient vehicle for carbon 

 tetrachloride is chopped elastic bands ; rubber imbibes the fluid readily 

 and retains it a long time. Crumpled paper toweling is also satisfac- 

 tory, especially when used in connection with light traps requiring 

 the efficient operation of large killing jars at least partly open to the 

 outside air. The heavy fumes arising from a paper towel saturated 

 with carbon tetrachloride will seek the bottom of the jar, which will 

 remain lethal throughout the night. 



Advantages : 



1. Produces fair to good relaxation. In this respect it is better 

 than either cyanide or alcohol. 



2. Assists in the extraction of oils and fats. 



3. Prepares the specimen for genitalic examination by causing ex- 

 cessive swelling when subsequently dropped into ether, an event usu- 

 ally resulting in the extrusion of the genital apparatus. 



b. Ethyl acetate (acetic ether). — For all general purposes, this is 

 an ideal killing agent. Its advantages when used as such were first 

 pointed out to the author by Prof. Candido Bolivar, whose technique 

 was to half fill a collecting tube with coarsely ground cork moistened 

 (not wet to the point of adhesion) with the ether. Strips of paper or 

 pieces of cotton tape moistened with ethyl acetate and placed in a 

 vial are equally effective and are better for very small specimens. 

 A still more efficient method is to introduce a half inch or so of wet, 

 mixed plaster of paris in the bottom of a tube or vial. Allow the 

 plaster to set ; dry it thoroughly in an oven ; then saturate it with 

 ethyl acetate, pouring ofT any excess fluid after complete impregna- 

 tion. A collecting bottle of this sort may "stand up" under months 

 of use, if not left uncorked. When exhausted, it can be dried again 

 in the oven and recharged with ethyl acetate. It is advisable to allow 



