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Museum pests can really bug

September 25, 2015

wasp with frass
Frass, often the indicator of a problem, is the sandy-dusty leavings of pests. Here, carpet beetles were feasting on the carcass of a wasp.


"Snug as a bug in a rug." Have you ever wondered what this expression actually looks like?

Many objects found in historic homes are tasty treats for the larvae of clothes moths and carpet beetles. Unlike adult moths and beetles, which you may see flying around the room or on windowsills, these larvae like to hide away in dark, undisturbed places. They are quite voracious and will eat wool, hair, feathers, silk, leather, fur, and dead animal or insect carcasses.

As the larvae eat, they leave behind small piles of excrement mixed with the material that they happen to be eating. This sand-like residue is called frass. Small piles of frass under castors, rugs, or other objects indicate a pest problem.

At Historic New England, when our collection services team finds an infestation in a museum object, we thoroughly inspect and clean the room (or, in some cases, an entire house) and transport the infested objects to our collections facility in Haverhill, Massachusetts.

There, the objects undergo an anoxic environmental treatment process to eradicate the pests. Once the treatment cycle is complete, each object is carefully vacuumed and then returned to its house museum. Sticky traps and insect pheromones help us keep an eye on insect activity and monitor each house for signs of additional outbreaks.

  • To learn about other types of museum pests, visit
  • Historic New England's carbon dioxide pest treatment system is available for rental to museums and individual collectors. Learn more.
  • To help with the overall protection of Historic New England's unique collection and the fight against museum pests, please consider a donation to the Collections and Conservation Fund.
larva and frass
The frass on the table, the purple dusty-looking piles, were the first sign that the wool felt underside of this telephone might be having a problem. When the object was moved, the carpet beetle larva fell out of its dark quiet hiding spot.
Webbing clothes moth larva
Webbing clothes moth larvae are hard to see on the bottom of a carpet. The larvae are circled here for you to see.
Object with larva and holes
Here you can see the damage and loss of the wool felt on the underside of this telephone.
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Museum pests can really bug