How to Tell How Many Instars a Caterpillar Has?

Caterpillars transform into butterflies in a little over a month. The metamorphosis from egg to butterfly involves a middle-growth stage. The middle stage is known as the larva -- or caterpillar stage. During the larva stage the insect grows in length and width; and in result sheds -- or molts -- old skin. Instars are intermissions between molt periods. Determining how many instars a caterpillar has is a simple process -- providing you have a ruler handy.

Things You'll Need

  • Magnifying glass
  • Ruler
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Instructions

    • 1

      Locate caterpillars on fresh outdoor foliage. Examine branches, leaves, pedals, and stems on nearby plants and bushes. Caterpillars eat greenery for nutrients and are often found on plants and shrubbery.

    • 2

      Find a resting caterpillar. Resting caterpillars sit stationary in their naturally elongated position. Moving caterpillars twist and buckle -- making them hard to measure.

    • 3

      Measure the length of the caterpillar from end to end. Examine the body length measurement to determine the caterpillar's instar stages: Instar One will measure between 2 mm to 6 mm; Instar Two measures 6 mm to 9 mm; Instar Three measures 10 mm to 14 mm; Instar Four measures 13 mm to 25 mm; Instar Five measures 25 mm to 45 mm.