The Household Casebearer is…a little weird. It’s also one of the most common pests we get asked about.

Written by Joe Ballenger
Household casebearer

Photo of household casebearer, from AaE inbox.

We get a lot of questions about household pests, and the biology of these pests can be a bit…weird. Most live in dry areas, and have a lot of adaptations to deal with it. It’s also a good way to be preadapted to human habitation, because our dwellings tend to be very dry and typically don’t have a lot of food.

One of the more common insects we get in our inbox is the insect above, the household casebearer. It’s often confused with clothes moths, although it doesn’t feed on fabrics. It’s a different critter altogether.

The early literature on this species is actually full of misidentifications, and it’s biology isn’t very well known. However, as far as entomologists can tell, it appears this species originated in either Africa or Australia and has hopped around the globe with people. Outside of it’s habitat, wherever it’s found, it’s usually found in association with people…and it doesn’t typically dwell far outside human habitations.

In it’s native habitat-or at least what we think it’s native habitat is-it’s found in conjunction with spiders. The caterpillars tend to live under spider webs, eating the leftovers the spider tosses out when it’s done. In addition to dead insects, it also eats silk from abandoned spiderwebs, webspinners, and other silk producing insects.

From here, it’s pretty easy to understand how this insect could get into houses. There’s a number of spiders which live in houses, which include cobweb builders like Pholcus and Steatoda. In addition, most houses contain some amount of dead bugs which come in from outside and can’t quite gain a foothold.

As a result, control is pretty simple…find and get rid of any cobweb building spiders, and do some deep cleaning in those forgotten recesses. However, it’s also a pretty cool bug. It feeds off the traces other bugs leave behind, and has spread all over the world because of it’s unique lifestyle.

Works Cited

Heppner, J. B. (2005). Notes on the Plaster Bagworm, Phereoeca uterella, in Florida (Lepidoptera: Tineidae). Holarctic Lepidoptera, 10(1-2), 31-32.

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