Six spot spider beetle Ptinus sexpunctatus

Adult

Size: 3-4mm

Shape: round thorax, round body. Spider-like.

Colour: Dark brown with white patches, three on each wing case.

Antennae: Long, no club

Distinguishing features: Wing cases with lines and hairs, spider-like.

Larvae are scavengers of: dried food and dead insects.

Damage: Not known

Adults eat: Very little but do drink water and are long lived

Note: This spider beetle is uncommon in houses in the UK.
These seem not to be museum pests.  There does seem to be a connection between the presence of this species and the Masonry bee Osmia rufa - they have been found in bee nests.
Ptinus sexpunctatus on trap

Six spot spider beetle Ptinus sexpunctatus

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Ptinus sexpunctatus on trap