Insects that don't eat, how do they make more insects?

July 12, 2016 9:26 PM

Some insects live short lives and don't eat or even have mouths. How do they breed? Wouldn't you run out of insects eventually if there's no input into the system of insect breeding as a whole? If I built and set free autonomous robots programmed to "breed" by assembling new robots out of each other, and they built other robots without picking up any spare parts or materials, wouldn't I eventually run out of functioning robots? What am I missing that this is so confusing? There has to be a logical answer to this.
posted by blnkfrnk to Science & Nature (9 answers total)

Best answer: They eat in their larval stages and save the energy for when they won't have a mouth.
posted by dilaudid at 9:32 PM on July 12, 2016 [19 favorites]

Can you be more specific about which species you're thinking of? Many species of mayflies don't eat, but that's true only in the adult stage of their lives. As larvae, they're eating and taking in energy.
posted by Paragon at 9:32 PM on July 12, 2016

Moths with no mouthparts eat and grow in their larval stage, consuming enough to support their (brief) post-larval life.
posted by russm at 9:34 PM on July 12, 2016

Best answer: This adult moth has no mouth. But when it was a caterpillar, it had a mouth and ate a lot. The moth form just flies around, breeds, and dies.
posted by fings at 9:35 PM on July 12, 2016 [2 favorites]

With animals like this, the caterpillar or grub or whatever is more like a 'normal' animal, which lives for a good while and eats and all that stuff.

Then, at the end of its life, it turns into a sex-having machine which has no use for a mouth.
posted by showbiz_liz at 9:41 PM on July 12, 2016 [2 favorites]

Best answer: Think of it as a delegation of organs through different life stages. The early stages of many insects, like some flies and moths are that pure stomach: They eat. That's all they do. Their bodies are primarily committed to chewing, digesting and excreting. They don't move very much, just eat.
The adults of these non feeding species are pure gonads. They fly (except for when they don't*) only as a means to reproduce.
*see females of the Rusty Tussock Moth, who are basically stationary ovaries when adult.
posted by Cold Lurkey at 9:43 PM on July 12, 2016 [2 favorites]

Response by poster: THANK YOU. I knew I was missing a piece. It was keeping me up, too.
posted by blnkfrnk at 10:37 PM on July 12, 2016 [2 favorites]

The luna moth only lives for 5-7 days and spends most of that time fucking. Then it dies. What a life. It eats as a caterpillar though. Considering they don't live that long I've been lucky enough to see three lunas in my life. They are truly beautiful.
posted by Brittanie at 3:48 AM on July 13, 2016

..."a sex-having machine which has no use for a mouth."

Yeah, well....
posted by mule98J at 9:59 AM on July 13, 2016