Written by Nancy Miorelli
The internet is chock-full of advice for collecting and if you’re looking to build an insect collection but can’t take a formal class, there’s lots of available help.
I myself, have a YouTube series dedicated to helping budding entomologists put together their first collections.
But there are always those awkward middle steps that seem to be left out of the conservation. I don’t think anyone means to, it’s just we’ve all found our methods that we like the best. However, for someone just starting out, those steps can be really important. Since it’s almost spring here, and people might want to start collecting, I thought this would be a good time to write about this.
I received this series of questions asking about all those bits that aren’t usually mentioned in collecting tutorials.
Before we get started, insect collections are used for many purposes including outreach and research. I won’t be discussing the reasons for insect collections in this article, only how to do it. If you’re interested in why entomologists kill insects, you can read one of our previous articles here.
1) Plaster or Plastic?
The plaster kill jar just holds a charge longer. The Acetone (or Ethyl acetate if you’re fancy) seeps into the the plaster and lasts a lot longer than just a cotton ball in a plastic jar. Even if you don’t use the jar with the plaster, I’d suggest always using glass – like a jelly jar or a mason jar – because the acetone or ethyl acetate can melt the plastic and your insects can get stuck in it. Some newer killjars, like the ones sold on bioquip have a canister that secures into the top of the lid that contains the liquid and the substrate. This is helpful, because, while it’s not so much of a problem for the cotton ball, the plaster can take a long time to absorb all the liquid. The canister at the top holds everything so your insects don’t get all wet and stuck to the bottom of your kill jar.
As for acetone vs ethyl acetate, the ethyl acetate also holds a charge a bit longer than the acetone, but acetone is really easy to get and cheap because you can just grab some nail polish remover. If you’re just going to go out collecting for an afternoon every once and a while, a cotton ball/acetone gets the job done. If you want to make a long term thing of it, I’d suggest the plaster/ethyl acetate which can be found on the BioQuip website. https://www.bioquip.com/
You don’t have to use kill jars. One of the drawbacks of the kill jar is that it almost instantly kills things. I really only used them to subdue angry stinging things. The kill jar kills all insects really well, but can cause problems for insects with predacious diets. The oils and fats in their digestive system seep through their body when they die and discolor the exoskeleton. One way to help prevent this is to let them live long enough to poop and cleanse the system. Then you can put them in the freezer and pin them when it’s most convenient.
2) Caught them! Now what?
I always put mine in the freezer. You can store your insects in ethyl alcohol, but if you keep them there for a while, then want to spread the bugs , the alcohol can make them brittle and hard to move around. This can make it easier for your insect to break or become damaged. The freezer preserves them without the insects becoming too brittle, so it’s easy to pin them and move all their legs and wings around to make them look nice in a collection.
3) Butterfly Triangles
Butterfly (Lep) triangles are triangluar pouches made, usually out of paper, to store butterflies. You can use wax paper, or buy expensive (and not really necessary) glassine envelopes. You would use butterfly triangles for any kind of Lepodoptera (butterflies/moths). It’s mainly to keep the butterfly flat and prevent it from damaging the wings and/or rubbing the scales off. You can put the whole thing in the freezer and leave the butterfly in there until you’re ready to pin it.
Here’s a video about how to make butterfly triangles.
Alternatively, I tend to use ziplock beading bags for my bug catching. I like to stay really organized, so I put each bug in one bag. I then label the bag: where I was, the date, and the habitat I took the bug out. Then when ID it, I’ll write the ID on the bag too. You can use the ziplock bag for butterflies. I was told that, because the bags don’t allow airflow, the butterflies can mold inside, but I never had a problem with this. Some people just like to get a big ziplock bag and throw everything in, but I can’t handle that amount of chaos.
I also carry a hard plastic pencil case around me in the field in my backpack. I put my bags of bugs I’ve collected in the pencil case, and when I get home, slide the whole pencil case into the freezer. This prevents the bugs from getting damaged in the field. If you get them around the beginning of the “back to school season” you can get them for like a dollar.
4) Freezers vs Alcohol
Insects stored in the freezer are easier to move around later if you want to pin them. However, people who might want to do genetic work and need the DNA to not degrade will store the insects in alcohol. That being said, anything can be stored in alcohol if you don’t want to pin it right away or ever.
There are also a lot of insects/arthropods that don’t preserve well outside of alcohol. These include arachnids (spiders/daddy long legs/scorpions/etc…), soft bodied insects (termites, neuroptera [lacewings/dobsonflies], stoneflies, mayflies, caddisflies, fleas, lice…), and larva/nymphs (caterpillars, maggots, dragonfly nymphs…). If you don’t store these insects in alcohol, they’ll shrivel on the pin. In some cases the body can recede completely into the thorax. I’ve had some luck counteracting this, if you store your insects in acetone for a few days before you pin your insect. The acetone replaces the water in the insect and they dry faster.
Some people store things in alcohol that are really too small to pin, or are fragile and might break if pinned. If you want to pin soft bodied insects, you can soak them in alcohol/acetone first, then pin them and it helps them retain their shape when they dry. Otherwise, oftentimes the abdomen shrivels into the body cavity and it looks like half your insect disappeared.
5) Relaxing Chambers
If insects aren’t stored in a freezer or in alcohol, the insect will dry out. Their muscles become stiff as they start to dry. This is the process that makes insect pinning effective, however if they dry out before you can pin them, they cannot be pined and break very easily. People will use relaxing chambers to try and rehydrate the specimen so they can attempt to pin it. You can avoid having to do this by just putting your insects in the freezer when you get home. Most people just make their own out of a solo cup, and some damp cardboard/paper towel. You just have to make sure that your insect doesn’t mold.
This person uses a Tupperware, but it’s basically all the same.
6) Freezer Time
How long you store the insects in the freezer depends if you’re using the freezer to kill them or not. If it’s just storage however long you need. If you’re using it to euthanize the insects, at least 24 hours. Some insects are freeze tolerant and will wake up. Some of the bigger and heartier grasshoppers/moths you’ll probably want to leave in there for a few days.
I personally use the freezer to euthanize the insects. It seems to me, the most humane way to go about the process. Since they’re exothermic, their metabolism and everything slows down until they just go to sleep.
7) Thaw Time
Depends on how big the insect is. Little leaf hoppers thaw in a few minutes. Big moths might take 15-20 minutes. Just try and move them around. If they’re still really cold and resistant to moving then let them thaw out for a bit longer.
8) When Can You Pin the Bugs?
If you use a kill jar you can pin the insect immediately after. Just take the insect out and wait a few minutes before pinning. Sometimes they seem dead, but aren’t really. I usually put everything from the kill jar in the freezer for a day just to be sure. I had a wasp wake up on me once and it’s not something I’d like to repeat.
In some cases, extra measures have to be taken when preserving insects. For really large tropical insects, oftentimes the guts have to be removed so the insect doesn’t mold. I don’t have any experience with this, so if anyone does, feel free to chime in in the comments below.
I hope this was helpful! If you guys have anymore questions feel free to leave them in the comments and I’ll be happy to tackle them =D If you have any advice too, please leave it below in the comments! This kind of stuff you usually learn about in class, so it can be hard for people to find this information =)
Here’s some collecting bloopers. Enjoy =P