Collecting Insects: Making an Insect Kill Jar

Insect kill jars are an essential piece of equipment for anyone making an insect collection and allow the collector to quickly and easily dispatch the insects they find in the field.  While it is possible to make a very simple kill jar that contains only a paper towel soaked in a killing agent, it is nice to have a more permanent jar so you’re not getting the fluids all over your bugs.  You can buy pre-made jars from entomological supply companies such as Bioquip (bioquip.com), but they’re cheap and easy to make yourself!

Note: I use different jars and different chemicals depending on the age of the people I am going to work with.  The set of instructions presented here are for children 12 and older and adults.  Instructions for adapting the jars for safe use by younger children are included in the notes section at the end.

 

supplies

Kill jar supplies

 

Things You’ll Need:

  • large wide-mouth jar with a one-piece metal lid (pasta sauce jars are perfect!)
  • plaster of paris (about 1/2 cup – available at craft supply stores , online, and sometimes at Target or Wal-Mart type stores)
  • water
  • disposable cup
  • disposable spoon or knife
  • paper towel
  • killing agent (more about this below)

To make the jar:

To make the jar easy to see into, it’s best to remove the label if your jar has one.  Soak the jar in warm water for about 30 minutes to soften the label, then peel it off and scrub away any leftover adhesive.  Wash and dry the jar.

 

jar

Empty, clean jar

 

Working quickly, mix the plaster of paris and water in the disposable cup using the disposable spoon or knife.  Follow the directions on the plaster package or use about 1.5 parts plaster to 1 part liquid.  I’ve found that using slightly wet plaster makes better jars than using thick plaster because it traps air inside the plaster and makes it more porous, but it does take longer to dry.  I usually start with about 1/2 cup of plaster and add water, stirring gently, until the plaster is pourable, about 1/4 cup.

 

mixed plaster

Mixed plaster

 

Carefully pour plaster into the jar until the plaster is about 1/2 inch deep.  If you get plaster on the sides or top of the jar, wipe it off as soon as possible if you don’t want it to remain there permanently.

 

dry plaster

Jar with wet plaster

 

Allow plaster to dry.  If your plaster package says you can microwave it, you can speed the drying time by microwaving for one minute and allowing it to cool, then microwaving and cooling two more times or until dry.

 

dry plaster

Jar with dry plaster

 

Dribble your killing fluid into the jar and allow it to soak into the plaster to charge your jar.  Depending on how thick your plaster was when you poured it, this may take some time.  There are several options for killing fluids.  See the note below for more information to help you choose the fluid that’s right for you and the amounts you might want to use.

 

charging a kill jar

Charging the kill jar

 

After the killing agent has soaked into the plaster, add a paper towel, a tissue, or a small wad of toilet paper to your jar.  This gives the insects a place to hide and helps keeps them from eating one another or beating against one another inside the jar as they expire.

 

complete kill jar

Complete kill jar

 

Use your new jar.  If you’ve never used a kill jar before, never fear!  I’ll post a tutorial on how to use a kill jar soon.

Notes:

Killing agents

There are several different fluids you can use as your killing agent.  The one currently favored by many entomologists is ethyl acetate.  It kills insects very quickly without having to use a ton of fluid.  However, it is also mildly toxic (don’t breathe it in if you can help it) and not readily available in local stores.  If you wish to use ethyl acetate, you can purchase a big bottle of it from scientific supply companies such Fisher Scientific (fishersci.com) or VWR (vwr.com).  It’s expensive though ($350 or so for a 4L bottle), so if you only need a small amount, purchasing it from Bioquip (bioquip.com) is a lot cheaper.  They sell it in a little squeeze cap bottle (pictured in the image of me charging the jar above) that is easy to use and won’t break the bank.  Note that ethyl acetate is a solvent and it can strip color off of some surfaces.  It’s best to keep the ethyl acetate off your insects, so let the fluid completely soak into the plaster before you use the jar if possible.  It won’t discolor most insects, but it can discolor some of them.

There are also other options for killing agents that are more readily available.  Acetone-free nail polish remover is mostly ethyl acetate and works fairly well, though a bit more slowly than pure ethyl acetate.  It is also mildly toxic due to the chemical mixture and may discolor some of your insects.  Rubbing alcohol will also work, though you will need to use a lot more of it to make it work (a few tablespoons as opposed to a half teaspoon to a teaspoon of ethyl acetate or nail polish remover) and it also takes longer to kill your insects.  The latter may be problematic for some people, especially children, because the insects struggle for much longer before they die.  It also allows the insects time to thrash around inside the jar as they die, which can destroy delicate parts.  On the plus side, rubbing alcohol is relatively safe to use, very inexpensive, and available almost everywhere.  I’ve purchased it in tiny little general stores in towns of fewer than 100 people!

Bioquip has other killing agents available, but I have not used them and can’t comment on how well they work.

Making jars for children

Glass and small children don’t mix.  Ethyl acetate and small children also don’t mix.  If you want to create jars for use with small kids, here’s how to make them safe for use.

First, use a plastic jar with a screw top rather than a glass jar.  You can buy these from grocery stores, stores like Target and Wal-Mart, and kitchen supply stores.  They’re often available at craft stores as well.  Plastic containers don’t break as easily as glass when you drop them and are less harmful if they do, so they’re better options for use with children.

If using a plastic jar, you can’t use ethyl acetate because it will disintegrate the plastic over time.  Besides, it’s better if kids aren’t sniffing ethyl acetate (you know there’s a kid in every group that does this sort of thing!).  With kids, I prefer to use rubbing alcohol.  It doesn’t work as quickly as a killing agent, but it won’t destroy a plastic jar and it’s much safer for use with children.

Recharging your jar

All of the killing agents I suggested are volatile and they evaporate a little every time you open the lid of your jar.  Thus, you will need to recharge your jar often to keep it working at peak capacity.  I recharge mine before every trip by adding more killing agent to the jar.  If you use your jar for several hours, you might need an additional recharge.  If you know you’re going to be out for more than a few hours, bring some extra killing agent with you and recharge your jar in the field.

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15 thoughts on “Collecting Insects: Making an Insect Kill Jar

  1. This looks like a really cool kill jar! When I first read the title of this post I thought it was going to be about those plastic bottles that people use to catch bees and wasps. This one is cool too!

  2. Hi! I am a biology student in the Philippines and I am about to do an assessment of dragonflies and damselflies as part of my thesis. Uhm…it will be my first time doing this kind of study and I am having a problem of what type of aerial net should I use in order to capture them or what size is most preferable ( the diameter of the opening and the length of the handle). Moreover, which chemical should I use to collect and kill them and which is best in preserving most of their colors seeing that their color, from what I read, easily fades off once killed .
    I am a novice and lacks experience on this..so I really, really do need some help from experts like you. I believe that you may be able to help me on this study of mine. And if possible, that is, that I could ask for a few more of your assistance in the future in identifying them…I would really, really appreciate it so much! Thank you, thank you so much! As in!

  3. I’m curious as to why non acetone nail polish remover will eat away a plastic kill jar. I’m just starting and bought a bottle of remover and the container it came in is….plastic

    • Ethyl acetate degrades some types of plastic, but works fine in others. I don’t know exactly which ones, so I just recommend that people use glass jars. That way they don’t have to worry about whether the plastic they’ve chosen is going to degrade over time or not.

  4. Try my kill Jar. It is better and cheaper to make if you don’t have to pour out the freeze dried coffee. It kills with alcohol. It is two parts the catch jar has holes drilled in the lid and it is placed upside down on an 18 oz cup with a paper towel. The design of the Folgers jar makes a seal as it is put down in the tapered cup. If you catch something in a net you can position the net over the cup with the insect in the center and push the 8 oz. coffee jar down on the net. This helps with the big wasp. I killed a butterfly and the net held the wings spread and it died in decent shape. It was the silver spotted skipper posted on my site. The cow killer was caught and died in the jar.There is never danger of the insect getting into wet fluid if you keep the condensate dried out of the jar between uses.

  5. thank you sooo much very helpful im doing a arthropod project for honors biology and i was going to buy a kill jar but i researched how to make one and your site was the best!!!!

    • If you’re just going to use it once or a few times, any container you can seal the vapors of your killing fluid inside long enough to kill the insect should work. A lot of the killing fluids will eat through plastic or rust metal coffee cans though, so you certainly wouldn’t want to use something like that long term. Of course rubbing alcohol works pretty well as a killing agent and doesn’t dissolve plastics, so you could always use that. It does take longer to kill your bug, however.

      Hope this helps!

  6. Great article and well explained, thank you!
    Just a note about using plastic jars: low- and high-density polyethylene (identified by the recycling codes ‘2’ or ‘4’) and polypropylene (recycling code ‘5’) are safe to use with ethyl acetate or acetone. Other plastics including PVC, polystyrene and PET are not.

    • Yes! Thank you for adding this! It always seems easier just to mention that plastics don’t always work with ethyl acetate than to go into the specifics, but I appreciate your adding this note.

  7. Just beginning to take an interest in collecting and preserving insects. You mentioned in the notes section about posting a “How To Use”. I can’t seem to find it, did you end up doing so and if not what is the proper method? Thank you!

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