Knowledgebase

Phone 1/16 - Moth eggs during the winter -- what to do #891634

Asked January 16, 2025, 9:19 AM EST

Caller said that she discovered an Isabella moth (90% sure it's an Isabella moth) in a head of lettuce from market. She placed it in her terrarium, expecting it to live only a short time. When she checked on it, she discovered that it has laid eggs ... pearly white, probably 100 or so. She wonders what is best for the eggs given the time of year, the indoor terrarium (and there's also the possibility of an glassed-in porch, which would provide cooler temps).

Merrimack County New Hampshire

Expert Response

Hi, Kelly -- Thanks for reaching out to UNH Extension Yard and Garden Infoline about your unexpected visitors! The information that I found indicates that the eggs should hatch in 5-12 days. When tiny, the caterpillar finds food by ballooning with a wisp of silk, or using it like Tarzan’s vine to get to the next batch of leaves.

As explained in the links below, fall larvae feed for several weeks and then "freeze" to overwinter, awakening when the weather turns warmer. If your Isabella moth eggs hatch, it seems it would be best to feed them for several weeks in relatively warm temperatures such as you have in your indoor terrarium. Please see the following links for more information.

Raising Woolly Bear Caterpillars (Isabella Moth)

Raising Woolly Bear Moths

What to look for during the overwinter stage (from Washington State University):

Woolly Bear moths

Best of luck with the unexpected guests! Please feel free to contact us again if you have additional questions.

Thank you for contacting the Infoline, a service of UNH Cooperative Extension. Replied January 16, 2025, 9:59 AM EST