Things You'll Need
- Magnifying glass
- Ruler
Instructions
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.
Find a resting caterpillar. Resting caterpillars sit stationary in their naturally elongated position. Moving caterpillars twist and buckle -- making them hard to measure.
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.