[personal profile] snarp
Bugs don't actually ever "develop a resistance" to pesticides, right? The fleas aren't actually "getting immune" to the old pet flea meds? These things aren't antibiotics, they're poisons that eat through the little things' chitin and eggshells and stuff. How exactly are you going to overcome that?

Bacteria are able to develop immunities to antibiotics that because their life-cycles are really, really short - they evolve really fast. Also, because huge populations of them are constantly being bomboarded with huge quantities of antibiotics due to Industrial Shit I Do Not Actually Understand, so there's plenty of opportunity for one bacteria to come up with a helpful mutation to resist a specific antibiotic and reproduce a lot.

Bugs don't live long, but they live at least a few days, which means population-wide genetic changes are going to take orders of magnitude longer than they do for bacteria. And they've got other places to live than on crops and domestic animals, and we're not spraying pesticides in the forest or giving flea pills to deer.

So I feel like if bugs are "learning" anything on a genetic level, the majority of survival-conducive mutations that actually get passed on are going to be the ones that tell them to stay away from humans and our stuff, rather than tiny changes that make their exoskeletons a little tougher in the face of something corrosive.

Evolution likes path-of-least-resistance shit like that, right? Even if a flea all of a suddem mutates up a total resistance to pesticide X, and that mutation doesn't impact them negatively otherwise, and that flea survives contact with said pesticide and breeds, it's not going to do as well reproductively as another flea on a deer in the forest that's got another mutation that tells fleas to slightly prefer deer/raccoons/bears/etc over dogs/cats/horses/etc. The forest flea has plenty of potential mates because no one's given its deer any Frontline-or-generic-equivalent-thereof; the house flea, in a house where most of the other fleas just got massacred, obviously has fewer opportunities.

(I feel bad for the mutant flea now...)

The only way I can see the "fleas get used to pesticides" narrative making sense is if some of the pesticides actually are antibiotics, and they function by messing up a symbiotic bacteria that lives on/in fleas, and that bacteria is actually the thing that mutates...?

But even then, it would have to be slower, because so few fleas ever come in contact with flea killer in the first place.

Anyway, I refuse to buy still-under-patent flea killer anymore because the generic stuff is fine.

Date: 2016-01-05 05:23 am (UTC)
From: [personal profile] sara
No, drug resistance actually is a thing. What happens is you kill all the bugs that are susceptible to the poison. Yes, even the ones in the woods, because the woods aren't actually very far away from anywhere else in this fucked up modern world of ours. The bugs that survive go on to breed.

Evolution happens damn fast in short-lived populations and the amount of toxin you need to have an impact in any given watershed is often way smaller than one might expect. I was at a fairly horrifying talk a few months ago about how much petroleum it takes to mutate salmon and it's depressingly little.

Date: 2016-01-05 06:49 am (UTC)
From: [personal profile] enemyofperfect
I have no idea what I'm talking about either, so this isn't a correction, but the sense I get is that evolution doesn't really push populations towards living well, it just pushes them towards living and reproducing in any possible way they can. Organisms are constantly trying completely unreasonable shit just in case it actually works, and then if it remotely does, no matter how terrible an idea it is, they and their descendants just keep on doing it, and usually getting better at it over time -- so even if you had fleas clever enough to avoid hosts that humans actively applied poisons to, that would just mean whatever fleas did find a way to exploit that niche would make out like bandits (albeit bandits increasingly adapted to a toxic wasteland).

This is moderately demoralizing from the perspective of someone who cares about the welfare of all living creatures, including the ones that make really terrible personal decisions, but I guess maybe the random accident that is the universe wasn't designed with my own personal worldview in mind.

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