Is killing mosquitoes a sin? I kill a lot of them everyday at home. Thye are present in a swarm every evening inside the house. I feel bad at killing them, but then otherwise the whole night is miserable without proper sleep.
Some creatures do need to be controlled — and mosquitoes definitely qualify. The reason is not just sleep, but that mosquitoes often carry diseases. Our real problem comes when we feel anger toward the creatures we must control. Here is how Yoganandaji’s guru put it in Autobiography of a Yogi:
“This world is inconveniently arranged for a literal practice of ahimsa. Man may be compelled to exterminate harmful creatures. He is not under similar compulsion to feel anger or animosity. ... Man’s body is precious. It has the highest evolutionary value because of unique brain and spinal centers. These enable the advanced devotee to fully grasp and express the loftiest aspects of divinity. No lower form is so equipped. It is true that one incurs the debt of a minor sin if he is forced to kill an animal or any living thing. But the Vedas teach that wanton loss of a human body is a serious transgression against the karmic law.”
Yoganandaji’s amusing comment on these words was, "I sighed in relief; scriptural reinforcement of one’s natural instincts is not always forthcoming."
You can read the full episode at: http://www.ananda.org/inspiration/books/ay/12.html