Are your eyes playing tricks with you, or did you just see what looks like a crawling pumpkin seed? No, it’s just a household casebearer! This seed-shaped, case-bearing caterpillar is not an uncommon sight in our area. Homeowners often bring these curious creatures into our office for identification. The silken, particle-covered cases offer camouflage and protection for the caterpillar as would a shell for a hermit crab. This nuisance pest can be managed with minimal concerns.
The name “household casebearer” almost has a royal ring to it, rich with purple velvet gold-trimmed images of relative grandeur! In reality, this lowly creature is actually a type of case-bearing moth caterpillar destined to crawl on its belly. You can find these insects in the presence of spider webs, in bathrooms, bedrooms and garages. They may also appear in association with wool rugs and carpets. The adult moth is tiny, gray and about ten millimeters long. Female moths lay up to two hundred eggs which hatch into caterpillars in about ten days. These caterpillars build a flat, spindle-shaped silken case and attach particles of sand, soil, rust, hairs, or other fibers to the outside. The caterpillar is protected inside and can stick its head out of both ends of the case. It can also reach out and pull itself and the case along as seen in the video below. The caterpillar eventually attaches itself on a wall and pupates. Do not confuse this insect with the similar, but different, bagworm found outside on lanai screens and walls.
What kind of damage can household casebearers do? Well, first of all their main nuisance issue is their peculiar appearance which can cause concern to homeowners. The main food item for these caterpillars is surprisingly old spider webs! They may even eat the old cases of their ancestors. Studies have shown that household casebearers will eat wool and similar natural fibers if given the chance. Accordingly, management of this insect would include regular cleaning to remove spider webs. Handpicking of cases and vacuuming will also reduce populations. As household casebearers are related to clothes moths, inspection and protection of woolen and similar items may also be advisable. As household casebearers require high humidity for development, air conditioning will also help suppress populations.
Household casebearers are a curiosity that should not evoke panic. They are an easily managed nuisance pest that can be controlled culturally. For more information on all types of household pests, you can also call the Master Gardener Volunteer Helpdesk on Mondays, Wednesdays and Fridays from 1 to 4 pm at 764-4340 for gardening help and insight into their role as an Extension volunteer. Ralph E. Mitchell is the Director/Horticulture Agent for UF/IFAS Extension Charlotte County. He can be reached at 941-764-4344 or firstname.lastname@example.org.
Villanueva-Jimenez, J. A. & T. R. Fasulo (2020) Household Casebearer, Phereoeca uterella (=dubitatrix) Walsingham (Insecta: Lepidoptera: Tineidae). The University of Florida Extension Service, IFAS.