As with many of the other questions here, different vegans may have different answers to this. However, I can discuss where I am on the issue:

If insects aren’t posing any danger to me, then no, I don’t kill them. But, unfortunately, as I discussed elsewhere regarding “life-or-death situations,” sometimes a person can encounter an unfortunate and unavoidable “us vs. them” situation with a dangerous animal. And in those cases — sorry, other creature, I’m going to choose me.

BUT! There’s plenty that I can do, proactively, to try to make sure that I never find myself in an “us vs. them” situation, whether it be real or imagined. I consider it my responsibility to be informed about insects, so that I never cause them unnecessary harm out of fear or ignorance.

Education

Many times we kill insects (particularly ones who have wandered into the household) because we are afraid of them. We’re afraid that this is a harmful insect, and we think that it needs to be destroyed, asap.

But in fact, the vast majority of insects in your house can do you no harm. And in certain cases, it’s really dangerous to that insect’s own survival for them to be trapped inside, and they want to get out even more emphatically than you want them out!

But spiders, tho.

You might be surprised by how few dangerous spiders live in your area. There are only two dangerous ones in the area where I live, and I’ve never encountered either one of them in person. Even the really “bad” ones are extremely unlikely to hurt you, even if provoked, because venom is a precious resource that they want to reserve for their prey. Rather than assuming the worst about that spider in your house, make sure you’re familiar with which spiders in your region are harmful, and their associated behaviors. Odds are, you have nothing to fear from that fellow on your window.

I know that spiders can be scary. After all, we grow up with stories where the spiders are the bad guys, and there really are some spiders out there that can harm us. But spiders aren’t plotting to come get you — having an encounter with you is way more dangerous to the spider than it is to you! Spiders have no reason to seek you out, or to try to crawl into your mouth while you’re sleeping — these are just spooky fictions invented to creep kids out.

Spiders are actually pretty cool creatures. Did you know that some spiders can see the moon? Also, the spiders in your house need your help. Because spiders use body fluid pressure to move, if they can’t find enough food, they will get so dehydrated that they can no longer move their legs, and once immobilized they will slowly starve to death (if you’ve ever seen a curled-up-looking spider body in your house, this is what has happened). That’s a terrible way to go! Please help these guys avoid that fate by moving them outside.

I highly recommend my trusty cup method: grab a cup and a sturdy piece of card stock, like a piece of junk mail or one of those magazine inserts. Put the cup over the spider wherever he is on the wall, wait for him to move away from the lip of the cup, and then gently slide the paper between the cup and the wall. Tip the cup away from the wall, holding the paper over the cup’s mouth, and take the spider outside. Uncover the cup and shake the spider out — the spider will understandably book it out of there! — and you’re all set. (If you’re nervous about spiders, that’s ok. Everybody’s nervous about something or other. Just see if there’s someone else in the house who can help you free the poor fella.)

Avoidance & Deterrence

Mosquitoes

Mosquitoes love me. If I’m in a mosquito-heavy area without sufficient protection, I’m going to get a bunch of bites. But do you know what has zero impact on how many bites I get? Killing the mosquitoes who are biting me. I haven’t noticed any difference between how bitten-up I get now that I’m not killing the mosquitoes, compared to when I used to kill them. I was killing ones who had already bitten me, since that’s how I could feel where they were, and then other mosquitoes that I hadn’t killed yet would just bite me elsewhere. Whatever swatting I was doing sure was making me flail around and smack myself, but it wasn’t making a measurable dent in the onslaught.

What does make a huge, positive difference in the amount of bites I get is being smart about exposure. If I’m camping, I pay attention to which times of day mosquitoes are most active in that area, and I try to arrange to be in a place where they can’t reach me during that period (either a mosquito-netted tent/hammock/sitting area, or a zone they don’t like, such as a windy bluff).

Mosquitoes are also really wimpy fliers. If I notice mosquitoes around, I can easily just jog for a short stretch and lose them. That isn’t feasible when, say, sitting around a campfire, but it works pretty well for hiking or otherwise wandering around the outdoors. Blowing on them works pretty well, too. (Many tips about avoiding mosquitoes I’ve gotten from Jains, who have been figuring out skeeter avoidance techniques for a long time.)

But sometimes there’s a situation where mosquitoes can’t be avoided. In those cases I use picaridin bug repellent, which I’ve found to be effective, and it isn’t harmful to humans, insects, or the environment as far as we can tell, in contrast to repellents that are known to be harmful like DEET. Certain other “repellents” like permethrin actually kill the insects on contact rather than just repelling them, and are dangerous to wildlife, so I don’t use those.

Ants

Step 1 is to avoid making your home appealing to ants. If you put food and dishes away, rinse recycling items, and sweep up crumbs, your house will be really boring to ants, and they’ll have no reason to set up shop.

If ants do come in, I typically remove them by sucking them up with a hand-held vacuum and then emptying them outside. (Obviously it’s a good idea to check first whether the hand-held vacuum hurts them — a tumble into my cheapo $20 model barely phases them.) After a few days of this, they’ve typically had enough. I do worry that by moving these ants outside, away from their colony-mates, that I may be condemning them to a dangerous fate. I’m not sure what the structures of interdependence are within the colony, and whether these relocatees will be ok. But this is currently the best solution I’ve figured out. (Open to suggestions!!)

But sometimes, despite my best efforts, it really is me vs. them

Disease-bearing mosquitoes

I’m lucky to live in an area where there isn’t a particularly elevated risk of contracting a really scary mosquito-borne disease like Zika. If I did live in one of those areas, I would most likely get traps to kill mosquitoes, and take other more extreme measures than I do here. However, I also support solutions that get more to the root of the issue, either by developing immunizations for humans against mosquito-borne diseases, or by certain novel strategies that actually ‘cure’ the mosquitoes themselves, so that they’re no longer vectors.

But yeah, in cases where I’m at a high risk of becoming seriously ill from a mosquito bite, I’m going to try to kill them. I’m sorry, guys — it’s not your fault. I wish this weren’t the case.

Ticks

Ditto for ticks. The risk of contracting a really nasty disease from a tick bite is high enough that I’m very vigilant about them. I do my best to avoid them in the first place: pants tucked into socks, picaridin, not brushing up against vegetation. But if I do find a tick on me, and I’m somewhere like the bathroom, where there’s no easy way to toss it outside, I will flush it down the toilet. Again, sorry, guys. I hope modern medicine figures out a solution soon, so that I don’t have to be at odds with you.