Why do some insects only live for a day?

We received this question from Stu on Facebook. It was over to Eleanor Drinkwater from the University of York for an answer and zoologist Jacob Dunn and vet Stuart Eves was able to relate nature's ability to adapt!

Eleanor - Basically it’s because they are brilliant. And they are just amazingly adapted to be able to carry out the entirety of reproduction that most mammals and other animals take ages to do, they’re so well adapted that they can do it just within 24 hours or a couple of days. So if you think about the different adaptations that this species come up with, so you have a mass emergence. So they all emerge at the same time so they can easily find a mate. The emergence sites are where they can also lay their eggs. They don't need to find a site to lay their eggs and also their bodies are completely adapted to finding a mate. So while they are looking for a mate they don't actually have working mouth parts. They can't actually feed. So they are just entirely focused on finding a mate. So the answer is, it really is, because they can do everything that they need to within that really short time frame.

Stuart - Sorry I have to just say that one of the most heartbreaking things I've ever seen watching a nature documentary, is they went through the entire life stage of the mayfly. And there was the point where it just rose out of the water in its flying stage, I presume. And then the trout came up and got him. And of all the documentaries I've seen you think oh that's such a shame because, what's the kind of ratio between how long they're in their kind of larval stage and then when they actually fly for the day.

Eleanor - Well I'm not sure but you get a lot of invertebrates which have a really long larval stage and then they only emerge for a few days. So for example the beetle which I mentioned before, the Titan Beetle which I've studied. It can live, they estimate it lives as a larvae for like five possibly 10 years and then it emerges for two weeks and then dies which I just think is amazing. But I think it's the journey, not just the destination. You know? It might be great being a larvae.

Chris - Aren’t on some cicadas, like that? Don't they have a sort of prime number ratios where they come out every 13 years or so some of them. and they've been underground for that long and then they come out do their thing, mate, and then that's it for them.

Eleanor - I don't know about cicadas precisely but there are some amazing adaptations to be able to to work out when everybody else is emerging at the same time it's just crazy.

Chris - It's like coral spawning I suppose. Jacob?

Jacob - I was going to say, I think there are some vertebrates that have similar strategies as well maybe you guys can help me out a little bit. I'm struggling to think of examples. But I think maybe octopus as well, and whether they're called Semelparous species that basically have a one off reproduction in their lifetime and they go all out and they have millions and millions of gametes and they just go crazy and then they die pretty much immediately afterwards. Whether you guys can help me out with any more examples.

Stuart - You know certainly my line of work, yeah we breed more often I guess in the mammalian side of things.

Chris - Cheers Stuart.