Prepared to break out of the laboratory and get back into your fieldwork? Make sure you’ve got your collection equipment at the ready. Aerial insect net? Check. Neoprene screw-cap collection vials (you can buy this from any biological supply house)? Check. Forceps and collection containers? Brilliant. It’s time to wrap your fingers around your favourite sweep net (with a wooden handle around 24 to 36” long, or a collapsible metal one) and get to it.
Fortunately, you won’t be alone in exploring the dark, squirming matter that consumes and nestles in the crevices and corners of the human cadaver. We’ve taken the liberty of collating all the information you’ll ever need to conduct a thorough study of insect activity and succession on the human cadaver. Remember: the data that you collect is immensely valuable to coroners and medical examination — so you’ll have to adhere to the protocol as closely as possible.
If you’re suited up and your gear is packed in the car trunk (or boot, depending on where you are), read on for your guide to ensuring the insect evidence retains its integrity.
1. Being out in the open, or providing scene observations.
Step one? Look closely at your surroundings. The notes you scribble down should include the general habitat (what type of ecosystem is it?) and the location of the body. Describe the vegetation situated around the body. To what extent is the region touched by sunlight or hidden by shade? Are there any open doors or windows, if you’re recovering samples from within a structure (a shed, or a bedroom)?
Begin recording the point at which the insects are in their life cycles — pinning down whether you’ve seen eggs, larvae, pupae or adult activity. It’s also important that you note any animal scavenging, so that this interference is evident when you evaluate your data.
2. What’s the weather like? Describing meteorological data.
Fumble for your thermometer now (ensuring that you don’t expose it to direct sunlight in the process) and take the ambient air temperature. You’ll want to hold it at chest height whilst standing in the shade. Then, without losing your breakfast, place the thermometer directly into the area of highest maggot activity — otherwise known as the “larval mass center.”
Additional measurements you’ll want to take include the ground surface temperature, the soil directly underneath the body when the cadaver is removed, and the temperature between the body and the surface its resting upon. Weather data should also be researched — you ought to find out the maximum and minimum daily temperature and rainfall for a period up to two weeks before the victim’s disappearance and up to five days after the body was discovered.
3. Counting and collecting, or removing the specimens.
It’s time to get up close and personal. The first insects to be collected are adult flies and beetles (being among the first to reach a body during decomposition). These insects move quickly and can leave the scene fairly rapidly once they sense another presence — which is why nets are handy to entrap them. Once adult flies and other species of interest have been caught, the closed end of the net (with the insects inside) can be placed in the mouth of what’s called a “killing jar.”
This jar, which should be prepared beforehand, contains cotton balls or plaster soaked with ethyl acetate (or nail polish remover). It’s capped after the insects are placed inside it so they’re immobilized within a few minutes. You’ll then want to transfer the species to a vial containing 75% ethyl alcohol. Beetles are slightly easier, as you can collect them with forceps and drop them into the last vial directly.
4. Labelling and wrapping it up.
A dark graphite pencil should mark out each identified specimen on these jars when you’re finished taking the relevant samples. Ink should be avoided, since the moisture in open spaces and the alcohol in the jars can cause it to lift off and run — in which case, you might be left with unmarked containers.
Your Turn: Want to share what happens after samples have been collected? Care to remind us of a critical step we’ve missed? Let us know in the comments. We’d like to hear from you.