How many mosquitoes are sucking blood?

Several mosquitoes are sucking blood. In the poem, it is a night off in May. Hungry mosquitoes still camp, but they will beg for blood. Do you feel that life is light? It means: at midnight in midsummer and May, people have already rested, and only hungry mosquitoes are still flying around. They only know how to suck human blood, so they don't care about cherishing life.