louse

louse (Pediculus humanus)

head lice

many fleas, but unconcerned (idiom); no point in worrying about one debt when one has so many others

woodlouse

louse (esp. a sucking louse)

very thorough search (for contraband, escaped convict, etc.)

tick (Acari spp.)

tropical rat mite (Ornithonyssus bacoti)

tick fever

cheese mite

psylla (any insect of family Psyllidae)

sugi spider mite (Oligonychus hondoensis)

hairy mite (esp. red velvet mite, Trombidiidae spp.)

spider mite (any mite of family Tetranychidae)