Frass

Definition

The solid excrement of insect larvae and other arthropods, typically consisting of digested plant material, wood particles, or other substrate combined with metabolic waste. Frass serves as a diagnostic field sign of larval presence and feeding activity, particularly for concealed feeders such as wood-borers, leaf-miners, and stem-borers. The physical characteristics of frass—color, texture, granularity, and placement—often permit identification of the producing species or higher taxon.

Etymology

From German Frass, meaning 'feed' or 'devour,' related to the verb fressen (to eat greedily, used for animals).

Example

A pile of fine, sawdust-like frass accumulating at the base of a tree trunk indicates active infestation by cerambycid or buprestid beetle larvae tunneling in the heartwood; lepidopteran caterpillars produce discrete, pellet-like frass that accumulates beneath host plants or within rolled leaves.

Synonyms

• insect feces
• larval excrement

Related Terms

• Feces
• guano
• borer
• leaf miner
• gall
• Mandibulate
• digestive tract

Usage Notes

Frass is distinguished from general feces by its restriction to larval stages and its frequent use as an ecological indicator; in rearing contexts, accumulation of frass signals healthy feeding and may require cage cleaning to prevent mold growth. The term is not typically applied to adult insect excrement (e.g., honeydew, meconium) or to liquid excreta.