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 (, 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.



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.



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.


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 ( or VWR (  It’s expensive though ($350 or so for a 4L bottle), so if you only need a small amount, purchasing it from Bioquip ( 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.


Print, save, or e mail this tutorial in PDF format!  Click on this link and the PDF will appear in a new tab or window.


Unless otherwise stated, all text, images, and video are copyright © 2010


New Feature: Collecting Insects

My collection

One unsorted box of my insect collection

This semester, I am the teaching assistant for an insect systematics course and an insect biology lab.  As part of the requirements for both courses, the students are expected to make an insect collection and identify all of their specimens to order and/or family.  We have a surprising number of students who haven’t ever taken an entomology course before, so they haven’t ever made bug collections.  Due to their inexperience, I get questions I never expected.  For example, one day I had to demonstrate how to use an insect net when a student asked how to catch a bee.  It didn’t even occur to me that she might not know that running around with her kill jar in one hand and the lid in the other trying to catch the bee might not be the best way to do it, but that’s what she was doing!

I’m teaching many of my students how to do a lot of things that I, a person who’s been a serious collector since she was 12, take for granted.  I love doing this sort of thing!  Because I have been collecting for many years, I’ve come up with a lot of shortcuts and easy ways to make things at home that work just as well as the professional equipment but at a fraction of the cost.  It’s been fun to share some of the things I’ve learned with my students.

Considering I’m doing a lot of this already, it occurred to me that it might be worth putting some of my instructions for making and/or using equipment online so that other people might benefit from them.  Thus, I’m starting a new feature called Collecting Insects!  Part of my goal in creating this blog was to provide an accessible educational resource, and this new feature will help me fulfill this goal.  I wish to share what I know to help make insect collecting more enjoyable for others, regardless of your level of expertise.

Here’s how it’s going to work.  I’m going to put the tutorials online  as regular blog posts so they are available to everyone on the internet.  Each post will cover the materials needed, discuss where you can get some of the more obscure components, and include detailed instructions with photos for each step.  I’ll also put a printable copy of each tutorial on my Educational Materials page.  These files will be in PDF format and will be accessible for teachers and other educators to use in classrooms – or for anyone else who would prefer to have a printed copy of a tutorial!  Please feel free to share any of the tutorials in any way you see fit as I am making them available to everyone without any restrictions on their use.

damselfly adult

Pinned damselfly adult, side view (Enallagma boreale)

Some of the topics I wish to cover will be how to make insect killing jars (next post), how to make simple insect nets, how to use various nets to catch different type of insects, how to collect aquatic insects, how to create and use a blacklighting rig, how to pin insects, and how to properly label your insects.  If anyone has any suggestions for topics they’d like to see covered, leave a comment below.  I welcome suggestions!

I’ll try to get a new tutorial up once a month.  If you have any interest in collecting for yourself or use insect collections in your teaching, I think this feature will be helpful.  Happy collecting!


Unless otherwise stated, all text, images, and video are copyright © 2010