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Band: pattern running around segments perpendicular to the body axis or more or less vertical markings on head.

Crochets: hooklike structures on the abdominal prolegs used to grasp substrate.

Deciduous: detaching readily.
Dorsal: along the back or upper side of the caterpillar.
Dorsum: back or upper side of the caterpillar.

Eversible: capable of being turned inside out or everted.
Extrusible: capable of being protruded or enlarged.

Frass: pelletlike excrement.

Granulose: appearing grainy; with sandlike texture.
Gregarious: occurring in groups (because female lays eggs in clusters). Many species are gregarious in the early instars, but eventually disperse and become solitary.

Hypoproct: Fleshy spur ventral to anus in loopers (Geometridae), especially in those that rest on twigs (see paraproct).

Imbricate: overlapping, like the scales of a snake.
Instar: one of the larval stages. Most species have 5 or 6 instars before molting to the pupal stage.
Integument: cuticle or skin of caterpillar.
Intersegmental: between adjacent segments; intersegmental coloration is often concealed when caterpillar is foreshortened.

Labrum: upper lip; the flaplike plate that rests over the jaws.
Larva: caterpillar; immature feeding stage of butterflies and moths and other insects with complete metamorphosis.
Lash: long tuft or fascicle of grouped setae.
Lateral: along sides, typically at level of the spiracles.

Medial: running along or near the body midline.
Midabdominal prolegs: prolegs arising from third to sixth abdominal segments.
Middorsal: along dorsal midline of body.
Midventral: along ventral midline of body.

Paraproct: small, fleshy protuberances on either side of anus in loopers (Geometridae), often held against substrate (see hypoproct).
Polyphagous: eating plants from more than 1 or 2 plant families.
Prolegs: fleshy "legs" usually located on third through sixth and tenth abdominal segments, typically bearing hooklike spines.
Prothoracic shield: dorsal plate atop the first thoracic segment.
Prothorax: first thoracic segment; segment to which head attaches.

Scolus (scoli): elongate projection, often branched and hardened, from body wall bearing minute spines.
Seta (setae): hairlike outgrowth from head or body.
Setal base: hardened plate at base of seta; pinaculum.
Spatulate: widened at the apex like a spatula.
Specialist: feeding on species in a single plant genus or 2 closely related host genera.
Spinule: minute spine, often broadened at base.
Spinulose: bearing numerous minute spines or cuticular outgrowths.
Spiracles: lateral, oval to round openings of respiratory system found on the first thoracic and first 8 abdominal segments.
Spiracular: adjacent to or passing through the spiracles.
Stemmata: lateral eyes, typically cluster of 6 on each side of head.
Stripe: pattern that runs longitudinally along body axis.
Subapical: back from or below the apex.
Subdorsal: to either side of the dorsal midline (see addorsal).
Subspiracular: below level of spiracles and well above prolegs (see subventer).
Supraspiracular: above level of spiracles.
Subventral: area above level of legs and prolegs but below subspiracular area (see subspiracular)

Thorax: consists of 3 segments immediately behind head that bear true, claw-bearing legs.
Transverse: running around a body segment, perpendicular to body axis.
Triangle: triangular plate located between the eyes and above the mouth (Figure 2); elsewhere called frontal triangle or frons.
Truncated: appearing cut or squared off.
Tussocks: dense tufts of setae, often appearing truncated and of 1 length.

Urticating: causing itching or burning sensation to the skin and eyes, often caused by entry of poison-filled spines (whose tips often break off).

Venter: underside or "belly" of caterpillar.
Vertex: dorsal or top portion of head.