Three short lines, and a tiny act of violence is already over. The speaker swats a mosquito the instant it bites. There's no buildup, no explanation, and no apology. The poem simply reports what happened, in a flat, matter-of-fact voice.
That flatness is what makes it interesting. The speaker doesn't seem angry or guilty, and doesn't celebrate. The killing feels almost automatic, a reflex more than a decision. Yet the phrase "pierced my skin" gives the moment a sharper edge than you'd expect from something so ordinary. It makes the bite sound like an invasion, which may be how the speaker justifies the reaction.
The mood is quick, dry, and slightly uneasy. The poem's brevity mirrors the speed of the swat, and its silence leaves you wondering how casually we take a life, even a very small one, when it touches us.