Unknown insect pupa or caterpillar stage

Asked May 20, 2020, 10:14 AM EDT

We found this insect in our garden and wondered what it is.

Benton County Oregon

1 Response

Thank you for the image. The object is a pupa of a moth.

The life cycle has 4 stages:
1. egg, sometimes laidsingle, othertimes in large batches
2. Larvae (youngsters) hatch from the eggs and are most often referred to as caterpillars which are are "eating machines" to ensure they have enough reserves to eventually become an adult.
3.Pupa is the "resting stage" during which the caterpillar transforms into a moth. This stage doesn't feed. Moth pupae are usually in the soil whereas butterfly pupae are typically above ground.
4. Adult moths emerge from the pupae, dig their way to the soil surface, wait briefly while their wings expand and dry, then fly away to locate a mate.

The only way to determine which moth this is can be a fun project, especially if you have youngsters:
1. Place the pupa in a covered clear container with a breathable lid, then set it aside until the moth emerges. (A simple lid is a paper towel held in place with a rubberband.)
2. Next, take several images and submit them to Ask an Expert for an ID.

My best guess of the ID at this time of year is the winter cutworm, Noctua pronuba. These caterpillars feed at night during the winter, whenever the temperature is above 40F. People often mistakenly think the damage is from slugs.

"Winter Cutworm: A new Pest in Oregon" has excellent images to help ID the larvae and adults. - https://catalog.extension.oregonstate.edu/sites/catalog/files/project/pdf/em9139.pdf