Submitted by Ramast t3_125nlmr in askscience

House flies are everywhere yet I have never seen a molten shell of a house fly ever.

They do have exo-skeleton so I expect them to molt.

I googled before posting this question but got no results

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That_Biology_Guy t1_je5rnu0 wrote

During development yes, but not as adults. All flying insects have determinate growth, meaning that they go through a specific number of stages before reaching a final adult stage, at which point they no longer grow. This is in contrast to some other arthropods (e.g. spiders, lobsters, and some non-flying insects like silverfish), which can continuously molt and never really stop growing. In all flying insects, only the final adult form is capable of flight (with the exception of mayflies, where the last pre-adult stage can also fly), so any time you see a flying insect, it's already in the ultimate stage of its life and won't grow any more.

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Sable-Keech t1_je89otl wrote

This applies to nearly all insects too. When an insect is unable to molt any more, then it usually means it’ll die soon since they can only really regenerate their organs when they molt. It’s why arachnids and crustaceans can live so much longer than most insects, because they can keep molting and hence rejuvenate themselves.

When insects injure their exoskeleton, the most they can do is exude a patchwork fix. When spiders and crustaceans lose an entire leg, they can regenerate it after a molt or two. The most primitive insects like silverfish have no metamorphosis and can keep molting as well.

It’s telling that the longest lived insects, termite queens, are protected by an entire colony and do not need to move around, minimizing the damage they sustain.

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