Preserving a beetle takes a few basic supplies and some patience, but the process is straightforward. Whether you’ve found a striking specimen in your yard or you’re building a collection, the steps are the same: humanely kill the beetle, pin or mount it in the correct position, let it dry completely, and store it in a sealed container that keeps pests out. Done right, a preserved beetle can last decades or longer.
Killing the Beetle Humanely
The simplest method is freezing. Place the beetle in a small container or sealed plastic bag and put it in your freezer for one to three hours. This kills the insect quickly without damaging the specimen. Freezing works well for most beetles and doesn’t require any special chemicals.
The other common option is a killing jar, which uses ethyl acetate (nail polish remover) fumes to kill insects rapidly. You can make one by placing a cotton ball soaked in ethyl acetate at the bottom of a glass jar, covered by a layer of cardboard or plaster to keep the beetle from direct contact with the liquid. The key timing rule: don’t leave the beetle in a killing jar for more than a day. Specimens left too long become soft and can fall apart, while ones removed too quickly and left unpinned become brittle and impossible to position.
Pinning a Beetle
Beetles are pinned through the right wing cover, about one-third of the way back from the head and slightly right of the midline. The pin should go straight down through the body and come out the underside. This is the standard placement entomologists use worldwide, so if your specimen ever ends up in a collection or needs to be identified, it will be mounted consistently with others.
For medium to large beetles, use size 2 or 3 insect pins, which you can buy from entomological supply companies. Regular sewing pins will rust over time and ruin the specimen. Stainless steel insect pins are inexpensive and worth the small investment.
Very small beetles (under about 5 mm) are too tiny to pin directly. Instead, use a technique called “pointing.” Cut a tiny triangle from stiff paper or card stock, pin the wide end of the triangle with a size 2 or 3 pin, then glue the beetle on its right side to the narrow tip of the triangle. A tiny drop of white glue or clear nail polish works well. Use forceps to position the beetle squarely before the adhesive dries.
Positioning the Legs and Antennae
Pin the beetle while it’s still flexible, ideally within a few hours of killing it. Push the pin through a piece of foam or corrugated cardboard so the beetle sits about three-quarters of the way up the pin, leaving room below for labels. Then use additional pins placed around the body (not through it) to gently hold the legs and antennae in a natural, symmetrical position. Spread the legs slightly outward so they’re visible and won’t overlap. This is largely an aesthetic choice, but tucked or tangled legs also make identification harder later.
Drying the Specimen
Once pinned and positioned, the beetle needs to dry completely before you move it. Place the pinned specimen in a covered (but not sealed) box at room temperature and wait. Small beetles dry in about a week. Medium and large beetles take roughly two weeks. You’ll know it’s done when the legs and body feel completely rigid and don’t give at all when lightly touched.
If you want to speed things up, a drying oven set to around 35°C (95°F) works well. Keep the temperature low. Higher heat can cause colors to fade or the exoskeleton to crack. Most collectors simply leave specimens on a bench or shelf and let time do the work.
Labeling Your Specimen
A preserved beetle without a label is essentially worthless for scientific or educational purposes. At minimum, every specimen needs a small label pinned below it on the same pin with three pieces of information: the location where it was collected (as specific as possible, including county and state or province), the date of collection, and the collector’s name or initials. Write the date with the month in Roman numerals between the day and year (for example, 15-VII-2024 for July 15, 2024) to avoid confusion across date formats.
Labels should be small. Professional entomologists typically keep them under about 22 mm long and 8 mm wide. You can print them on card stock in a tiny font or write them neatly by hand. A second label below the first can note the habitat, what plant the beetle was found on, or a species identification if you have one. Mount the location and date label closest to the beetle, since it’s the most important.
Long-Term Storage and Pest Prevention
The biggest threat to a preserved beetle collection isn’t time. It’s other insects, specifically dermestid beetles and carpet beetles, which will eat dried specimens from the inside out. You can open a drawer after a few months and find nothing but dust and pins.
The best defense is physical exclusion. Store your specimens in tightly sealed containers or purpose-built insect drawers with gaskets. Cornell-style drawers, used by museums and universities, fit so snugly they’re nearly airtight. For a home collection, a deep shadow box frame with a tight-fitting glass front works, or even a sealed plastic container with a foam pinning surface glued to the bottom.
Older collections relied on mothball chemicals like naphthalene or paradichlorobenzene placed inside drawers to repel pests. These work but produce strong fumes and pose health concerns with long-term exposure. Modern museum practice has largely shifted to tight-sealing cabinets that simply keep pests out mechanically. For a home collector, a well-sealed box stored in a dry room is your best bet. Check specimens every few months for signs of damage: fine powder beneath a specimen is the telltale sign of pest activity.
Keep your collection out of direct sunlight, which fades colors over time. A cool, dry environment with stable humidity is ideal. Excessive moisture invites mold; excessive dryness isn’t usually a problem for already-dried specimens.
Wet Preservation as an Alternative
Not every beetle needs to be pinned. If you want to preserve soft-bodied larvae, keep backup specimens, or simply skip the pinning process, you can store beetles in alcohol. The standard concentration is 70% ethanol, which preserves the external structures well and keeps the specimen intact for morphological study.
If you care about preserving DNA for future analysis, use 95% ethanol or higher. There’s a trade-off, though: higher alcohol concentrations preserve genetic material better but can make specimens more brittle. At 70%, DNA gradually degrades over months and years, especially at room temperature. For most hobbyists preserving beetles for display or identification, 70% ethanol in a tightly sealed glass vial is perfectly adequate. Top off the vial periodically, since alcohol evaporates slowly even through sealed caps.
Rehydrating a Dried Specimen
If you have a beetle that dried out before you could pin it, or you want to reposition an old specimen, you can soften it using a relaxing chamber. This is just a sealed plastic container with wet paper towels in the bottom, soaked in a mixture of equal parts water and 70% rubbing alcohol. Place a small dish or lid on top of the towels to create a raised platform, set the dried beetle on the platform, and seal the container.
After one to three days, the beetle absorbs enough moisture to become pliable again. You can then pin and position it normally. Don’t leave specimens in the chamber longer than necessary, because mold will start growing and can permanently damage the surface. Check daily after the first day, and remove the beetle as soon as the legs move freely.