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Insect Identification Key
Order Zygentoma (formerly Thysanura): the silverfish and firebrats

A silverfish
This silverfish (Lepisma saccharina) has the teardrop body shape and the three, long, thin “tails” typical of members of this order. Photo credit: Sebastian Stabinger. Click here to see examples of more insects in the order Zygentoma!

Based on your answers to the questions, you have identified your insect as being in the order Zygentoma (formerly Thysanura)!

Members of this order include: silverfish and firebrats.

Etymology: Thysanura comes from the Greek thysano-, which means fringed or bristled, and ura, which means tail. Thysanura, therefore, means "bristled tail," which is a reference to the three caudal filaments characteristic of these organisms. Zygentoma comes from the Greek zygon, which means bridge. It refers to the unfounded notion that this group of insects is an evolutionary link (or a bridge) between other orders of insects, particularly the winged insects and the unwinged insects.

General characteristics:
• wingless
• small insects, no more than 10 mm long (2/5 of an inch)
• three long, thin “tails”: one caudal filament (also known as an epiproct) extending straight out from the rear of the abdomen, flanked by two similarly long cerci that fan off to the sides
• small compound eyes, but no simple eyes (ocelli)
• typically a dorsoventrally flattened, tear-drop shaped body
• body often covered with silver scales
• long, thin, multi-segmented antennae
• three pairs of tiny appendages (known as styli) near the end of the abdomen
direct development (nymphs and adults nearly indistinguishable)

Click here to see examples of more insects in the order Zygentoma!

Number of species worldwide: about 370 (depending on how species are defined, some put the number at only around 200)

Kingdom Animalia
   Phylum Arthropoda
      Subphylum Hexapoda
         Class Insecta
            Order Zygentoma (formerly known as the order Thysanura)

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

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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