Ischnocera is a large parvorder of lice from the infraorder Phthiraptera. The parvorder consists of chewing lice, which feed on the feathers and skin debris of birds. Many species of Ischnocera have evolved an elongated body shape. This allows them to conceal themselves within plumage to avoid being dislodged during preening or flight. Species in Ischnocera spend their entire lives living on a host, and attach themselves to hippoboscid flies to help move across individual birds. Ischnocera contains the large family Philopteridae, along with a few other minor families. Ischnocera are distributed globally, with around 3,800 species identified. The lice are very host-specific, and each species rarely parasitizes outside of their preferred bird species. Birds infested by Ischnocera's species can experience discomfort and damage to reproductive systems.

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