The Burying Beetle’s

Guide to Parenting

A burying beetle (sexton beetle)
Image Source: Kent McFarland

Halloween is almost upon us, so The Nature Nook will be looking at creatures with more macabre and sinister behaviours than usual. We’ll be starting off proceedings with this insect, a burying beetle from the genus Nicrophorus. These fascinating little creatures are the recyclers and undertakers of the insect world. Even if we disregard the beetle’s rather ghoulish alternative names – the sexton beetle, the grave-robber beetle, the carrion beetle and so on – or even its classic orange and black Halloween colours, this insect still exhibits some morbid behaviour, especially when it comes to breeding and raising its young.

Here’s how a parenting guide for a burying beetle might look…

Step 1: Find a suitable corpse

Firstly, the burying beetle detects, using its extremely sensitive antennae, the smell of a small dead animal, perhaps a little bird or a mouse, and heads towards it. If a male discovers a suitable corpse and there is already a female present, the two will mate and move on to the next step. If he’s alone, he will release a sex pheromone to attract a partner. But if there are several other beetles already there, or if they arrive later on, they will often fight amongst themselves (male vs. male, female vs. female) to gain control over the carcass until one pair, usually the largest, emerges victorious.

Step 2: Hide the corpse

After working so hard to claim the corpse, the last thing the burying beetles want is for another animal to come along and eat it or take it away. So the beetles work together to defend it from other interested parties and then they start to bury it. They create a shallow pit around and beneath the corpse so that it falls into this underground crypt, effectively obscuring it from view.

The pair then embalm the corpse in antibacterial and antifungal secretions (from their anuses, no less) to slow down the decaying process. Both male and female will spend some time removing feathers and fur from the corpse until it looks like a compact, featureless lump of flesh.

A burying beetle (sexton beetle)
A sexton is a church officer charged with the maintenance of its buildings and surrounding graveyard. Among the traditional duties of the sexton in small parishes was the digging of graves, which is why burying beetles are sometimes known as sexton beetles. Appropriately enough, some of these beetles do indeed live in graveyards.
Image Source: Holger Gröschl

Step 3: Feed the babies

The female beetle lays her eggs on or near the buried carcass so that when they hatch a few days later, the emerging larvae can feed on its flesh. For a while, the larvae cannot tear off chunks themselves, so they rely on their parents to provide them with food. The adults partially digest the flesh first and then regurgitate the liquid carrion for their offspring. The young maggots may even rear up and beg for food like baby birds, especially if there are many larvae in the brood. This is one of the few examples of parental care in the insect world outside eusocial insects such as ants, bees, termites and wasps.

By the time the young have reached their third instar (growth stage), they are able to feed directly from the carcass. They tunnel into the corpse, gradually hollowing it out as they feed on the decomposing flesh. After feeding voraciously for several days, the larvae wriggle out of the remains of their carrion ball and burrow into the surrounding soil. There, they pupate, ready to emerge next season as adult beetles.

Step 4: Cull the babies (Optional)

However, the parent burying beetles aren’t always so blissfully nurturing. One day, as the larvae continue begging for food, the female may suddenly grab and eat one of her offspring. Has she finally snapped? Not quite. When the female originally laid her eggs, she could have no idea how much of the animal carcass would be lost to scavengers or micro-organisms, but she nonetheless optimistically laid a large clutch. If food later becomes too scarce to distribute evenly among her offspring, she must kill some of them to prevent all of them from being underfed. It’s all about maintaining the perfect balance.

Keep an eye out for more Halloween-themed articles at The Nature Nook for the rest of the week! I’ll be looking at two blood-sucking animals – the infamous vampire bat from South America and the strange, ancient lamprey from our own rivers and streams – while Alex will be looking into how to take care of the ghost mantis!

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