Definition
Frass is the technical term for insect waste or excrement, and depending on the pest, it's often mixed with fragments of whatever material the insect has been chewing through, like wood, paper, or fabric. It's a word you'll hear a pest control technician use during an inspection, especially when trying to pin down exactly which pest is responsible for damage, since frass doesn't just confirm that a pest is present, its appearance and texture can actually point to which specific pest it is.
Because different pests produce visibly different frass, a trained technician can often narrow down the culprit just from what's left behind, even without seeing the insect itself.
- Drywood termite frass looks like tiny, uniform pellets with ridged or hexagonal sides, pushed out through small "kick holes" the termites create to eject it from their galleries
- Carpenter bee frass looks like coarse sawdust piled beneath a round entry hole in exterior wood, like a fascia board or deck
- Cockroach frass often resembles fine coffee grounds or small dark specks and streaks left along surfaces where roaches travel
- Bed bug frass shows up as small dark or rust-colored spots on mattress seams and nearby fabric, often alongside shed skins
Finding frass during an inspection is one of the clearest physical signs of pest activity, and identifying its type correctly is often what determines the right treatment approach from there.