Western Tiger Swallowtail Larva 1st-3rd Instar - Papilio rutulus

Moved

Moved from Butterflies and Skippers.

… John S. Ascher, 4 October, 2016 - 6:28pm

Moved

Moved from ID Request.

… john and jane balaban, 1 October, 2016 - 8:22pm

4th

This would be 4th instar

… Dave Rogers, 29 September, 2016 - 8:01am

3rd Still i think

Have not found a molt yet? but growing very fast, stretches out very long when crawling or eating. then bunches up into a more protective position.

… Robert Gorman, 29 September, 2016 - 10:14am

Head

Look at the head to determine the instar.

… Dave Rogers, 29 September, 2016 - 4:37pm

instar.

How can I judge the instar by looking at the head? What should i look for to tell the difference? Thank Dave, Bob

… Robert Gorman, 29 September, 2016 - 11:56pm

Osmeterium

Nice series of photos!

The "horns" are called the osmeterium, an organ that swallowtail caterpillars deploy as a defensive maneuver. They're retractable, and not visible in this photo, where the caterpillar was more relaxed.

In addition to startling predators with the bright color and "forked tongue" look, the osmeterium also sprays smelly chemicals to repel predators.

BugGuide has a small page on osmeteria here, if you want to see some more examples from different caterpillars.

… MosquitoBait, 28 September, 2016 - 10:33am