A killing jar is a device used by entomologists to kill captured insects quickly and with minimum damage. The jar, typically glass, must be hermetically sealable and one design has a thin layer of hardened plaster of paris on the bottom to absorb the killing agent. The killing agent will then slowly evaporate, allowing the jar to be used many times before needing to refresh the jar. The absorbent plaster of paris layer also helps prevent the agent sticking to and damaging insects. Crumpled paper tissue is also placed in the jar for the same reason. A second method utilises a wad of cotton or other absorbent material placed in the bottom of the jar. Liquid killing agent is then added until the absorbent material is nearly saturated. A piece of stiff paper or cardboard cut to fit the inside of the jar tightly is then pressed in. Another design is shown on the right. This has to be recharged more frequently.
The most common killing agents are ether, chloroform and ethyl acetate. Ethyl acetate has many advantages and is very widely used. Its fumes are less toxic to humans than those of the other agents and specimens will remain limp if they are left in an ethyl acetate killing jar for several days and the ethyl acetate is not allowed to entirely evaporate from the specimens. A disadvantage is that although the insects are quickly stunned by ethyl acetate it kills them slowly and specimens may revive if removed from the killing jar too soon. Potassium cyanide or other cyanide compounds are also used, but only by experts due to its extreme toxicity. The potassium cyanide slowly decomposes, releasing hydrogen cyanide.
Killing jars are only used on hard-bodied insects. Soft-bodied insects, such as the larval stage, are generally fixed in ethanol at 70-80% concentration.
Famous quotes containing the words killing and/or jar:
“The most absurd apology for authority and law is that they serve to diminish crime. Aside from the fact that the State is itself the greatest criminal, breaking every written and natural law, stealing in the form of taxes, killing in the form of war and capital punishment, it has come to an absolute standstill in coping with crime. It has failed utterly to destroy or even minimize the horrible scourge of its own creation.”
—Emma Goldman (1869–1940)
“As soon as you begin to say “We have always done things this way—perhaps that might be a better way,” conscious law-making is beginning. As soon as you begin to say “We do things this way—they do things that way—what is to be done about it?” men are beginning to feel towards justice, that resides between the endless jar of right and wrong.”
—Helen M. Cam (1885–1968)