Hello,

The red blood stain after hitting a mosquito is because the mosquito has drank yours or some other animals blood. The mosquito feeds on blood, so which is why the red blood. That blood does not belong to the mosquito it belongs to someone else. Insects have a substance called hemolymph, which is similar in function to blood. Hemolymph is clear to yellowish in color, with its only pigmentation coming from plants and other materials ingested by the insect.