Thursday, 22 December 2022

Killing Insects the Safe Way

Folks making insect collections are always confronted with the problem "How to kill the specimens without destroying colour and structure".  Ethyl acetate has been used for years but it discolours green and yellow insects. It is a disaster when used to attempt to kill Lepidoptera. 

Many students  "freeze" specimens to kill them for their collections. But this is inefficient, especially when in the field. And the results are usually not satisfactory.

Potassium cyanide has traditionally been used to obtain the best specimens. It generally does not discolour insects (vespids an exception). But because of the danger to human life, it is usually not available without multitude of permits including inspection of premises where the cyanide is kept. In the Kuranda area, the fire department requires inspection and knowledge where the chemical is housed since in the event of fire, because of the toxicity of the chemical, they need to know the whereabouts of the cyanide. 

A solution to the problem has been found. Ammonium Carbonate works well as an insect killing agent. This is the "smelling salts" of the boxing trade. It is generally available from chemical warehouses and does not require a permit.  Occupational Health and Safety people have no objections with students using this chemical.

Ammonium Carbonate kills insects promptly and does not discolour most insects. Even green katydids and various hemipteroids are not affected by this agent. It does deliquesce if the bottle is not tightly sealed. If kept dry, this agent is perfect for Lepidoptera, even micros. In time the bottle may become moist on the inside. It pays to change the tissues regularly to avoid this happening. A tight-fitting lid is essential. 

One advantage I have found with Ammonium Carbonate is that the insects' muscles are generally relaxed and the appendages can be manipulated without them breaking off. The legs of Stick Insects (Phasmatodea) are often "deciduous" and fall off when manipulated. With Ammonium Carbonate, the legs stay on the specimen. 

Drink bottles are ideal for killing bottles. They come with tight-fitting lids and, if glass, the glass is heavy duty. (I have found that even the plastic drink bottles work but glass is preferred. Instant coffee jars are also useful.


An amount of Ammonium Carbonate is added with a disk of sponge or cardboard, slightly larger than the diameter of the bottle to keep the agent in place. Then some loose tissue strips are added to prevent the insects from damaging one another. With a little practice, you will discover which insects should be removed soon after they are killed and which insects can remain in the bottle for a bit longer, even overnight.

Drink bottle as a killing jar for small insects


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