Geometridae

Pronunciation:  [Geo·MET-ri⋅dee]

Common Name:  Geometer Moths, Inchworm Moths, Spanworm Moths

Description:    Adult geometer moths are small to medium in size.  They have slender bodies and broad wings which are usually held outspread and flat against the substrate with much of the hind wings visible.  Intricate wavy patterns on the wings are often continuous from forewing to hindwing.  Antennae may be feathery or thread-like.  Paired tympanal organs (ears) occur on the sides of the first abdominal segment, but are often covered by hair and difficult to see.  Ocelli are absent.  The subcosta of the hind wing makes a sharp downward bend near its base and the cubitus of the front wing appears to be three-branched (trifid venation).

This family includes many serious agricultural and forest pests.  Larvae are usually slender and twig-like.  They have only the last two pairs of abdominal prolegs and move by extending the front of the body forward and then bringing the rear up to meet it — hence the name “inchworm” or “spanworm.”

Spot ID Key Characters:

  1. Antennae filiform or pectinate
  2. Wings with wavy lines that are continuous from forewing to hindwing
  3. Tympana present on first abdominal segment
  4. Subcosta (Sc) of hindwing bends sharply downward near base
  5. Cubitus of front wing appears three-branched (trifid venation)

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Order:  Lepidoptera