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Caterpillars of Pacific Northwest
Forests and Woodlands

Photo Key to Species

Group A-1 -- One pair of midabdominal prolegs, on segment A6. All of these species are Geometridae.
- Group A-1a -- Body wall with lateral projections
- Group A-1b -- Subgroups: Body wall smooth
  - Distinct spiracular line
  - Dorsum color different than subspiracular area
  - Distinct subdorsal longitudinal lines
  - Middorsal area with a stripe or dots
  - Body with distinct patches of color
  - Body without distinct markings
Group A-2 -- Two or Three Pairs of Midabdominal Prolegs
- Prolegs on A5 smaller than those on A6
- Prolegs on A5 same size as those on A6
Group B-1 -- Without Dense Patches of Hairs
- Group B-1a -- Subgroups: Body wall with swellings
  - Middorsal horn absent on A8
  - Middorsal horn present on A8
- Group B-1b -- Subgroups: Body wall smooth, except monarch butterfly
  - Colors in rings
  - Straight longitudinal lines
  - Wavy longitudinal lines
  - Irregular middorsal markings
  - Spots, or streaks, or reticulated
  - No distinct markings
Group B-2 -- With Dense Patches of Hairs
- Group B-2a -- Subgroups: Hairs different lengths
  - Middorsal tufts of short, dense hairs
  - Sublateral long, dense hairs
  - At least half covered in long hairs
  - Less than half covered in long hairs
- Group B-2b -- Subgroups: Hairs very short
  - Humped in profile, head concealed
  - Not humped in profile, head exposed
Group B-3 -- With Sclerotized Spines
- Group B-3a -- Spines with a single point
- Group B-3b -- Spines with multiple tips
Pupae of Lepidoptera
Larva of a Sawfly

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Caterpillars of Pacific Northwest Forests and Woodlands

Photo Key to Species

Caterpillars of Pacific Northwest
Forests and Woodlands