What kind of effect would removing all species of mosquitoes or spiders have on the global ecosystem? [closed]

Question

Any kind of annoying pest really, but I chose arthropods because I hate them. And someone else hates them too. Let's say he's some sort of well-intentioned but reckless mad scientist who really needs to think his plans through better. He releases a lab-engineered genophage (probably made using CRISPR) that targets and sterilizes all species of a certain pest or virulent/invasive species. No other animals are affected, but within ten years, the genophage will have spread across the globe and those species will probably all go extinct within twenty years.

What kind of fallout are we looking at here? What kind of consequences would suddenly wiping out an entire family or clade of pest species have on the environment and the rest of the global ecosystem?

Answer 1

The usual path is predatory species (spiders) which go boom (large growth cycle) when prey is plentiful, making lots of healthy offspring. Then they kill everything in sight, leaving too many spiders, which leads to starvation (bust cycle) with spiders producing fewer offspring allowing their prey to rebuild their population. Rinse. Repeat.

In this case consider that many insects would lose their main, or a primary predator, they have no check on their upper population levels, e.g. lots of bugs. It does mean that certain wasps that prey on spiders would die out, or reduce their population as they find new prey.

Maybe someone working for an insect control company thinking that this will drive business up, kill the hated spiders while not thinking through the consequences.

Eventually evolution will solve the problem. Trouble is, evolution doesn't really care about humans so the solution might not be friendly to the insect control company or its mad scientist. :-)

Answer 2

Using mosquitos as an example, you can expect a pretty big ripple effect on the ecosystem.

They're a piece of the food chain, so if you wipe them out, you'll eventually harm/lose all the species that feed on them, and then the species that feed on the low level predators, and so on, and so forth on up the chain.

Mosquito larvae are eaten by minnows, minnows are eaten by larger fish, larger fish are eaten by humans. See how it only took three simple steps to effect the top of the food chain? Now obviously this is a simplified model there's loads of other things that eat mosquitos and loads of things that eat those things. The point is that you​ can't really remove any species without it rippling out across the the entire chain.