Whitemarked spider beetle (Ptinus fur)

Adults of the whitemarked spider beetle (Ptinus fur) are small, convex, spider‑like ptinids, very similar to other Ptinus species, notably the hairy spider beetle P. villiger. P. fur is reliably diagnosed by its elytral vestiture: the setae covering the elytra are all of uniform length, unlike in P. villiger where setal length is uneven. The body is ovoid with a domed pronotum and elongate legs and antennae typical of spider beetles. Larvae are white and apodous.

Damage in stored grain is dominated by silk webbing and granular frass. Larvae spin fine threads that entangle kernels into felted masses and crusts, obstructing grain flow and complicating cleaning. The granular residues—pelletized excreta and fines—accumulate as dusty deposits, contaminating the lot and downgrading market quality. In practice, operators notice matted clusters, strings of silk bridging kernels and sack seams, and pockets of gritty debris in bins and along storage surfaces.

Signs of infestation by the whitemarked spider beetle, Ptinus fur (L.), in stored grain: - Silk webbing and agglutination: kernels, fines, and dust bound together by silken threads, forming clumps, sheets, or narrow silk‑lined passages—evidence of larval and adult activity. - Endosperm (albumen) damage: irregularly contoured, bored perforations and ragged feeding galleries within the kernel, caused by larvae and adults. These features reliably indicate active P. fur in stored-grain lots.

Whitemarked spider beetle (Ptinus fur) undergoes complete metamorphosis. After mating, females practice concealed oviposition, depositing eggs in cracks and crevices near stored commodities. Neonate larvae are relatively gregarious, feeding in small clusters of 3–4 individuals within agglomerated grain. Once larval development is complete, they spin a silken cocoon and pupate inside it. Fresh adults eclose from the cocoon, then disperse, mate, and renew the cycle.

Prefers humid indoor habitats with dried organic detritus—chiefly warehouses and dwellings housing stored products. Reproduction needs high relative humidity; it is less often encountered in museums, attics, and silos.

Hairy spider beetle (Ptinus villiger) Other spider beetle species