First Instar
Body and head (x20)
| Color Pictures |
| First and Second Instar Comparison |
Body length: 2 to 6 mm
Body width: 0.5 to 1.5 mm
Front tentacles: Small bumps
Back tentacles: Barely visable
Head capsule: 0.6 mm in diameter
Appearance: A newly-hatched monarch larva is pale green or grayish-white, shiny, and almost translucent. It has no stripes or other markings. The head looks black, with lighter spots around the antennae and below the mouthparts, and may be wider than the body. There is a pair of dark triangular patches between the head and front tentacles which contain setae, or hairs. The body is covered with sparse setae. Older first instar larvae have dark stripes on a greenish background.
After hatching, the larva eats its eggshell (chorion). It then eats clusters of fine hairs on the bottom of the milkweed leaf before starting in on the leaf itself. It feeds in a circular motion, often leaving a characteristic, arc-shaped hole in the leaf. First (and second) instar larvae often respond to disturbance by dropping off the leaf on a silk thread, and hanging suspended in the air.
Egg | First instar | Second instar | Third instar | Fourth instar | Fifth instar