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Insect Identification Key
Order Psocodea/Superfamily Anoplura: the sucking lice

Head lice, various life stages
This photo shows five of the life stages of the head louse (Pediculus humanus). The left three insects are nymphs, and the last two are adults. The small bar at lower left represents 1 mm. Note that the head is narrower than the thorax, a characteristic on these insects. Photo credit: Centers for Disease Control/James Gathany.

Click here to see examples of more sucking lice!

Based on your answers to the questions, you have identified your insect as being in the order Phthiraptera, suborder Anoplura: the sucking lice!

Members of this suborder include: body lice, crabs (the insect variety, not the crustaceans) and nits.

Etymology: Anoplura comes from the words anoplos, which means unarmed, and oura, which means tail. This refers to the lack of cerci.

General characteristics:
• parasitic, feeding on the blood of mammals
• small
• wingless
• short antennae
sucking mouthparts, but they may not be visible because the insect typically protrudes them only when feeding
• a single claw on each tarsus
• a head that is narrower than the thorax
• small, often nonfunctioning eyes; in some species, the eyes are absent altogether
hemimetabolous metamorphosis (egg — nymph — adult)

Click here to see examples of more sucking lice!

Number of species worldwide: about 500

Basic ecology:
The sucking lice are parasites of mammals almost exclusively. They are ectoparasites, meaning that they prey on the host animal from the outside of the host’s body.


Kingdom Animalia
   Phylum Arthropoda
      Class Insecta
         Order Psocodea (formerly separated out into order Phthiraptera)
         Superfamily Anoplura

For a list of all of the orders in this key, click here: List of Orders.

Classification note: Anoplura was once described as its own order, and as a suborder within the order Phthiraptera, but is now considered a superfamily within the order Psocodea.

Oops! If this doesn't appear to be the order for your insect, go back through the key and look more carefully at your insect while answering the questions again. Your perseverance will reward you!

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Photos at the top of this website are (from left to right): potato beetle (Leptinotarsa decemlineata) — photo credit: Scott Bauer, U.S. Department of Agriculture; ebony jewelwing (Calopteryx maculata)— photo credit: U.S. Fish and Wildlife Service; sweat bee (Agapostemon splendens) — photo credit: Natalie Allen and Stephanie Kolski, U.S. Geological Survey; preying mantis, monarch butterfly (Danaus plexippus), hellgrammite (aka toe biter) larva and eyed click beetle (Alaus oculatus) — photo credit: Leslie Mertz; Halloween pennant (Celithemis eponina) — photo credit: Kay Meng, U.S. Fish and Wildlife Service.

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