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The_ChortleMachine t1_j5dqn10 wrote

Like the other comments say, we *think* most bugs die to predation rather than old age, but we (zoologists/ entomologists) really have no idea.

Its incredibly difficult to tell because its basically impossible to track individual bugs in the wild. Most of what we know about the lifespan of animals in the wild comes from mark-recapture experiments, where a large number of animals are captured, marked with something like a leg band or other tag, and then some amount of time later another survey is conducted to see how many tagged animals are re-collected. This works really well for populations of vertebrates and gives us a pretty good estimation of how long animals live, based on the dates on the tags or other long term records. However, as far as I know, its virtually impossible to actually do this with insects (right now, at least). Dobzhansky tried a couple times with wild fruit fly populations but never got anything conclusive, and that's the most well known attempt I know of.

In regards to lifespan, it can be highly variable, and depends on how you define lifespan. Most insects typically live actively for a couple days to a couple years, but some insects can be alive for much longer. Insects can enter a state of hibernation called diapause where they remain in stasis for years at a time, like cicadas which famously hibernate for 17 years. Depending on how you define lifespan, there are insects that are technically alive for decades, but they spend the vast majority of it in diapause in their cocoons and are only active adults for a couple days/weeks/months at most.

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Scharmberg t1_j5fau3b wrote

Why are they in stasis for so long?

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The_ChortleMachine t1_j5fd1jc wrote

Typically they're waiting for ideal environmental conditions.

Insects are ectothermic (cold blooded) so they can only operate when its warm outside, and many species use diapause to hibernate safely through the winter. Insects will go into diapause in their eggs or pupae (cocoons) which are much more resilient than their adult bodies, and build their pupae in safe, warm places like underground, deep in trees, or under decaying leaf matter where it doesn't go below freezing during the winter, emerging from their pupae when it gets warm enough.

Many insects also struggle to manage dehydration as adults, so they'll go into diapause during dry seasons and emerge as adults in the wet seasons.

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the_denim_duke t1_j5d0vzh wrote

More bugs likely die from predation in the wild than from old age, as many insects and other invertebrates have relatively short lifespans and are a vital food source for a wide variety of predators. Additionally, many insects have high reproductive rates, which can offset the loss of individuals to predation.

There are also many insects that have a long lifespan, and for those, age-related death is more likely. e.g. the Queen ant, termite, or honeybee, and Cicadas, Praying Mantis' etc.

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openly_gray t1_j5dg0ne wrote

Hard to tell, but arthropods are high on a lot of lunch menus so one would think predation cuts max lifespan short ( which is actually the case with most prey species since predators typically target the less fit meaning the old and the very young). It also depends if you count only the adult stage. Certain families, like mayflies have extremely short adult lifespans (days, its literally mate, spawn and die), so one could assume that more die if “old” age than through predation

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tomtink1 t1_j5dxv2c wrote

I was thinking about things like mayflies... Would it count as old age or starvation/exhaustion/exposure depending on what the reason the adult lifespan is so short?

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openly_gray t1_j5f92gw wrote

Technically “old age” since the short lifespan is a biological feature ( I believe some of them don’t even have a working digestive system). But that certainly can be debated

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