Why so much nastiness in the insect world?

Or perhaps, why so comparatively little nastiness in terrestrial vertebrates? Any science-fiction writer who wants to depict a nightmare world of unspeakably hostile alien life has only to have large-mass creatures behave like insects. I refer to such things as spawning one’s larvae in parasitized hosts; the female devouring the male after mating; swarms that devour every living thing in their paths; “eating” prey by dissolving and drinking their internal organs; luring prey to their deaths by faking the prey’s mating signals; and doubtless countless other predation and parasitation strategies that I can’t think of at the moment. By contrast, about the nastiest thing I can think of in terrestrial vertebrates is how some birds like cuckoos or cowbirds lay their eggs in other birds’ nests and the hatchlings kill the hosts’ chicks.

Insects have been evolving a lot longer than vertebrates; there’s been more time to develop weird lifestyles. And there are a lot more of them, so more opportunities for mutations to arise.

What about the yearly battles between mammal males over who gets lucky?

What about lions who kill cubs so that the lionesses will be sexually receptive?

What about people?

1.) It’s not just insects. The traits you mention are pretty common among the Small Things of the world.

2.) Small vertebrates can be almost as nasty as other small things. Naturalist Niko Tinbergen wrote about Water Shrews, whicvh he found fascinating. But he also found that they ate their kills alive.

3.) One reason big animals like, say, lions, are “humane” and kill their prey first is that they don’t like it kicking and squirming, especially if they comparable in size or larger than the lion. You can get killed by your own prey. Big animals kill their prey first because it’s easier and safer.

4.) Small things, on the other hand, eat a LOT more than their larger counterparts. In the case of shrews it’s because they have to maintain that high mammalian body heat in the face of a rotten mass-to-surface-area ratio. Shrews have to eat a LOT in order to stay alive, so they don’t have tinme for niceties.

5.) On the microscale things are much simpler than on the macro scale. It’s a lot easier for water beetle larvae to inject its prey with fluid to dissolve and suck out the juices – it’s a lot easier to eat a chitin-wrapped meal that way and there’s not a lot to digest. It’s hard to imagine, say, a Komodo dragon eating that way. It’s have to devote a huge prtion of its body weight in juuices (mostly heavy water) , it’d take a long time for it to percolate through the body and dissolve it, then suck it back down. It’s a hell of a lot more efficient to rip off chucks (wich aren’t protexcted by chitinous armor) and let it dssolve in juices in your stomache.

6.) Similarly for laying eggs in a host body. Ichneumon flies (wasps, really) can get away withn this because the host is opretty smasll and pretty simple, and the young mature fast. You couldnm’t see a lion, with its complex biology and its months-long gestation period, doing the same thing.
Being small gives you more options. Insects and tiny livestock take advantage of these niches. But, Alien and other flicks to the contrary, you can’t scale it up.
Have a look at The Forgotten Planet by Murray Leinster, in which humans coexist on a planet of scaled-up garden creatures.(Or any of the 1950’s “giant bug” flicks, like [BThem!**) Nasty stuff, but the square-cube law and other such considerations would keep this from happening.

Yearly? I witness it every weekend.

Isn’t it simply a case of what’s more familiar to us being fine, and what’s foreign being icky? So animals more like us aren’t icky? Think of the list a bug could come up with:

  1. Half of them give birth! What a waste of resources - every male has to support his own Queen!

  2. They give birth to larvae, not eggs! Wriggly, wet, bloody larvae that pees and poops almost imediately and

  3. They look after their young for YEARS before it can do any work at all!

  4. Now, you may not believe me, 'cause this is really disgusting, but their young drink secretions from enlarged sweat glands of the female!

And that’s just reproduction. I’m sure our living and eating habits are just as horrifying to your average anthropomorphized, literate ant.

<nitpick>

The only mammals whose milk-producing glands evolved from sweat glands are the monotremes (e.g. duck-billed platypi, mammals that lay eggs).

For all other mammals, including humans, the milk-producing glands evolved from sebaceous glands.

</nitpick>

[sarcasm] Oh. Well, never mind then. 'Cause sebaceous gland discharge sounds yummers.[/sarcasm]

(Actually, thanks. I got it mixed up in my noggin, and wouldn’t want to spread the ignorance.)

<<Shuts down computer and runs from room screaming>>

Just kidding. I like the little things, actually.

Comedy response: How many insects have you seen invade a foreign country on false information? :slight_smile:

Contribution to thread: Keep in mind that mammals, unlike insects, reproduce differently as well. Insects may have had evolutionary pressure to develop insect WMD because they reproduce so rapidly. Mammals, on the other hand, can make one calculated move and take out an entire generation.

This isn’t always true. I saw a documentary of a pride of lions that had taken to hunting elephants. The documentary crew was watching the lions as this new behaviour emerged. They filmed the first elephant eaten, a sick old elephant that couldn’t move anymore and the lions started eating from the hindquarters with the elephant vainly trying to get away.

Nasty stuff.

Oh, don’t act all innocent, you were flirting and egging John on and I’ve still got a fat lip. You’ll be back.

What about snakes? As far as nasty grossness goes, I think that suffocating or injecting poison into a prey animal bigger than your head and then coating it with saliva so you can slowly swallow it whole through your dislocated jaws while crushing it with your throat muscles is right up there with anything insects do. Eee-yuck.

Every form of life on the planet has been evolving for exactly the same amount of time. Assuming, of course, that there was only one origin of life.