Why do bugs die on their back – You Won’t Believe This

There are two distinct reasons that bugs seem to always be upside-down when they die: either they can’t get back upright and that’s the actual cause of death, or they find themselves dying the right way up and, when they lose control of their legs, end up flipping over due to being heavier on the top than in the legs. 

Most kinds of bugs naturally want to be upright, as their legs help them get to shelter, source nutrients and escape from prey. If they don’t have control of their legs, they will most likely die quickly. 

• Most bugs need to be on their legs, right-way-up, in order to remain alive
• A bug that starts dying upright will flip over due to being top-heavy
• Pesticide will shut down a bug’s nervous system, causing them to lose control and roll over, and also causing convulsions that prevent it from righting itself
• Cockroaches, beetles and spiders are some of the insects that most commonly die on their backs
• Bugs in the wild are less likely to die on their backs than bugs in your home

Why do bugs die if they get knocked onto their backs when they’re alive and healthy?

Bugs use their legs to access all of the things they need to survive: to get to whatever kind of food, water or nutrients they use as fuel; to access shelter from the elements; and to run away from prey or attackers.

If they don’t use their legs for these purposes, many of these bugs use their wings.

When you think about the bugs that most commonly die on their backs, such as cockroaches and beetles, you can see that they’re particularly heavy on the back (or dorsal) side of their bodies; comparatively, their legs are slim and light.

If they get knocked on their backs, it’s very hard to right themselves due to this imbalance in weight. 

So, when a bug gets knocked onto its back, and it can’t get back onto its legs, or is unable to open its wings and fly, it’s now unable to access nutrients and shelter, and unable to flee from predators. 

A bug that can’t get off of its back therefore can’t survive very long, and will most likely die in this position. 

If a bug starts dying upright, why does it end up on its back?

When a bug starts dying, blood will stop circulating in the normal way. Just like humans, normal functions begin to shut down, and when the blood stops flowing to its legs, the bug’s legs will begin to contract.

Unable to maintain control of its legs, the bug can no longer control its weight distribution, either – and as most bugs are top-heavy (think of a cockroach with its tiny legs and huge, heavy shell) – it will naturally roll onto its back. 

Sometimes, a bug is also weakened, sick or in some way compromised – so when it rolls onto its back, it’s just not at the full fighting strength it needs to be to get back on its feet. 

So, it’s not the bug’s natural flare for drama that causes it to roll onto its back as it dies – if it hasn’t died in this position, it’s just a simple matter of physics!

Why do bugs killed by pesticide always seem to die on their backs?

This one is a bit more gruesome, and has to do with the effect the pesticide has on the bug’s functions. 

Most pesticides, or more specifically, insecticides, work by interrupting the function of the nervous system of the insect. This causes the muscles in the bug to rest, and also causes spasms or convulsions.

Basically, the insect loses control over its muscles, and when it can’t control its legs, it will flip over due to the heavier weight distribution of its body. The convulsions prevent it from turning itself back the right way up. 

In the case of pesticides, it’s usually not the bug being on its back that kills it – that’s just the function of the pesticide on its nervous system. As when a bug starts naturally dying upright, ending up on its back is just a matter of physics. 

Which bugs most commonly die on their backs?

The bugs you might be most used to seeing die on their backs are cockroaches and beetles. You can see why this is – their heavy body and wings seem to make them very top-heavy, while their legs are comparatively very slim, light, and fragile. 

Spiders also have a tendency to roll over on their backs when they die, often with their legs curled inwards due to rigor mortis. When their legs curl in, the centre of gravity moves to the body, so they roll onto their backs. 

You’ll also see flies, crickets, and lots of other insects on their backs when they die.

Really, any insect that has that unbalanced weight distribution – slim, spindly legs and a heavy exoskeleton or set of wings on its back – if it’s top-heavy, the chances of it dying on its back are much higher. 

Do most bugs in the wild die on their backs?

Most bugs in nature actually don’t die on their backs – this is far more common in bugs that you find in your home. 

There are a couple of reasons for this. Firstly, most bugs in the wild are eaten by prey, and that’s how they meet their ends. So those bugs usually die in one distinct location – the stomach of a bigger animal!

Secondly, think about a forest floor vs. your kitchen floor. If a bug finds itself unexpectedly legs-up, it’s going to have a very different experience righting itself in the wild than in your home. 

If a bug falls on its back in the wild, the forest floor will provide all kinds of twigs, leaf matter, hairs and plants that a bug can use to leverage itself upright again or rock itself back onto its legs. 

Sometimes, though, a bug that is already sick or weakened will still not be able to right itself, even with all those helpful leaves and twigs to grab onto – so you will still see bugs in nature that have died as a result of rolling onto their back. 

However, if a bug ends up on its back on your sparkling clean tiles, it’s got nothing at all to grab onto or roll against to get itself back upright. Your home is actually a much more dangerous landscape for a bug than out in the wild!

So why do bugs die on their backs?

Bugs die on their backs for a variety of reasons – whether they’re knocked onto their backs and unable to get back up, start dying upright and rollover due to gravity, or are killed by pesticide and, similarly, rollover due to gravity – it all comes down to the weight distribution of their body and the fact that, when they lose control of their legs, it’s very hard for them to right themselves again. 

Alright, that’s it for this article, here are a few hand-selected articles that you might also find interesting reads:

Why Don’t Insects Drown? the Quick Answer

Why don’t insects die when they fall – The Curious Answer

Why Do Dead Flies Attract More Flies?