Geographic location of the bug: Browns valley, Ca. Near marysville
Time: 06:17 PM EDT
Your letter to the bugman: Last year we found unbelievable amounts of cacoons on surface of everything. Now we have these critters everywhere. What are they, what do they evolve into? Anything poisonous?
How you want your letter signed: Bret
This is a Tussock Moth Caterpillar in the genus Orgyia, but we are not certain of the species as there are several very similar looking species that are found in California. The adults are sometimes called Vaporers. BugGuide has images of the adult Vaporers as well as the egg masses. We have gotten several identification requests in the past few days, so we are posting your submission. According to Featured Creatures: “The medical importance of Orgyia species caterpillars is well-documented in the scientific (Diaz 2005, Gilmer 1925, Goldman et al. 1960, Knight 1922) and clinical dermatology (Hossler 2009 & 2010 ) literature. Pruritic (itching) dermatitis due to tussock moth caterpillars has been reported to be a problem at child day-care centers and elementary schools in Florida (Atrubin et al. 2012, Atrubin & Granger 2006, Cruse et al. 2007). Contact with the cocoons produces the same symptoms.
The caterpillars may be contacted when they drop from the host trees or when they wander from the trees in search of a place to spin their cocoons. Home owners develop dermatitis from contact with the cocoons while removing them from the soffits of houses. Hairs in the cocoons retain their urticating capability for up to a year or longer.
Most of the urticating hairs are in the dorsal tussocks of the caterpillars (Knight 1922), but a few are also found on the lateral verrucae and intermingled with the black plume hairs of the hair pencils (Gilmer 1925). Gilmer (1925) conducted histological studies of the urticating setae of Orgyia leucostigma and found that each seta has a venom gland at its base. The venom has not been adequately characterized.”