What else is classified as lice? - briefly
The term “lice” also covers chewing lice (Mallophaga), which feed on skin, hair, or feathers, and aquatic lice (Argulus), which parasitize fish. Both groups are ectoparasitic arthropods distinct from head and body lice.
What else is classified as lice? - in detail
Lice belong to the order Phthiraptera, a group of obligate ectoparasites that feed on the blood, skin, or feathers of vertebrate hosts. The order is divided into two suborders: chewing lice (Mallophaga) and sucking lice (Anoplura). Both suborders contain numerous families and species that infest mammals, birds, and occasionally reptiles.
Additional arthropods commonly referred to as lice, though not true members of Phthiraptera, include:
- Marine copepods (e.g., Caligus and Lepeophtheirus species). These parasites attach to the skin of fish and are called “sea lice” in aquaculture.
- Amphipod crustaceans (e.g., Talitridae species). Often called “sand lice” or “beach lice,” they inhabit coastal debris and feed on detritus rather than host tissue.
- Mites of the family Demodex. Frequently termed “eyelash lice,” they reside in hair follicles and sebaceous glands of mammals, including humans.
- Poultry ectoparasites such as Menopon spp. and Goniodes spp., labeled “feather lice,” which consume feathers and skin scales of birds.
- Fur lice (Haematopinus spp.) that infest domestic animals like dogs, cats, and livestock, feeding on blood.
- Human body louse (Pediculus humanus corporis). While a true sucking louse, it is distinguished from the head louse (Pediculus humanus capitis) by its habit of living in clothing seams.
Key characteristics shared by true lice:
- Wingless, dorsoventrally flattened bodies.
- Mouthparts adapted for chewing (Mallophaga) or piercing-sucking (Anoplura).
- Direct life cycle: egg (nit) → three nymphal instars → adult, all occurring on the host.
- Host specificity varies from strict (e.g., human head louse) to broader ranges (e.g., some feather lice).
Distinguishing features of non‑Phthiraptera organisms called lice:
- Copepods possess swimming appendages and a free‑living larval stage absent in true lice.
- Amphipods exhibit laterally compressed bodies and lack specialized mouthparts for blood feeding.
- Demodex mites are microscopic, elongated, and inhabit internal follicular environments rather than the external surface.
Understanding the taxonomic boundaries clarifies why certain parasites acquire the “lice” label despite differing phylogenetic positions. The term therefore encompasses a range of ectoparasitic arthropods united by their external, host‑attached lifestyle, but only those within Phthiraptera meet the strict scientific definition of lice.