Tenebrio molitor Linnaeus, 1758
Common throughout the UK but in our experience has become less so over recent decades. Large size and dark colouration make this difficult to miss, it flies into illuminated rooms at night and usually crawls on ceilings or high on walls. Breeds in stored products and bird nests or bat roosts in houses, the larvae being the familiar yellow mealworms sometimes sold as live petfood. Although seemingly most at home around human habitation it is also found in the wild. A common species during the summer around Watford town centre when it is attracted to light and enters houses. Several specimens have been attracted to MV light in Whippendell wood from May to September.

12-18mm, width 4.5-6mm. Usually dark brown to almost black but light brown specimens are not uncommon, these remain light when kept alive. Entire upper surface punctate and somewhat shining, punctures on elytra distinct with the flat cuticle between them shining (X20). Without pubescence. Antennae short, not reaching back to the base of the pronotum, joints 3 and 4 elongate, 8-10 transverse. Apical joints of antennae and front tarsi often lighter in colour. Protibia curved, sexually dimorphic; longer and more curved and with ventral surface flattened and produced at the apex in Male.

In the other British species, the uncommon T.obscurus Fabricius, the elytral punctures are so dense that the surface appears rugose and dull

Description from 2 Watford specimens at X20