Head louse (nit)

Human scalp and hair follicles

Obligate ectoparasite; feeds exclusively on human blood several times a day

Nits are glued to the hair shaft near the scalp; adults crawl quickly but cannot jump or fly; life cycle takes about 30 days from egg to death

Causes scalp itching (pediculosis) and secondary skin infections from scratching; not known to transmit diseases; no benefits to humans or ecosystem