What are the conditions that allow killing animals out of self-defense?

Dear brothers and sisters My question regards the type of animals that at first glance don't cause any fatal harm to a human being So, I wondered for a while if it is allowed to kill mosquitoes who sting you to feed themselves with your blood. I often kill them and cite Surah Al-Ikhlas 3 times and then throw them away in the dustbin. And I also wonder now if it is permissible to kill animals who bite you without any physical harm except for a scar. (E.g. non-venomous snakes, fire ants, non-venomous spiders, etc...) Please show your source as you explain how you should deal with those type of animals. Thank you in advance