These insects are only 2mm long and are attracted to all vertebrate species by the trail of carbon dioxide that is exhaled as they breathe. Humans serve as good large CO2 emitters. The first contact you may have will be with pregnant females that will land on bare skin, which they bite through to feed on your blood. The midges then leave to lay their eggs. After this you may have a reaction, with some itchiness and small pink spots caused by sub-cutaneous bleeding, due to a tiny amount of anti-coagulant left by each of the midges at their feeding sites.