Reesa vespulae (Milliron, 1939)

The only member of the genus Reesa Beal, 1967 and native to the Nearctic region, this species began to appear in Europe during the 1950’s; the first record was from Germany in 1957 and it has since become widespread, especially in the north, including the U.K. Scandinavia and Iceland, and eastwards through Asia Minor, Russia and Afghanistan. Further afield it is now established in Japan, Australia, New Zealand, Mexico and Chile. In cooler climates, including the U.K., it generally occurs in domestic premises where the adults may be found at windows etc. in the spring and summer. In Europe it is known to infest a wide range of products including various stored seed and plant material, museum specimens and dead insects. There are scattered records of the species occurrence in the wild but in general it is synanthropic, inhabiting human dwellings and stores etc. In the Nearctic region it is mostly a wild species occurring in bee hives and other hymenopteran nests where larvae develop on dead insects and detritus. It rarely causes damage in domestic situations although it can be a pest of dried fruit, and large populations can establish in cellars where they feed upon fungi growing on exposed wood. The larvae are just about omnivorous, being able to develop in a wide range of stored food products, and they are very distinctive among the dermestids being small, up to 6mm, pale brown to yellow, pubescent and with a ‘brush’ of very long golden hairs at the abdominal apex. The species is thought to be parthenogenetic as males have never been found and the females lay eggs that develop to complete the life cycle without being fertilized.

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This small species, 2-4mm in length, is distinctive due to its long-oval shape and colouration; head and pronotum shiny black, elytra dark brown at the base becoming lighter towards the apex and with a transverse band of light brown or yellowish pubescence in the basal third which does not extend to the suture. The entire upper surface is finely punctured and clothed with fine, semi-erect and curved pubescence. The antennal cavities are shallow and poorly defined, situated on the front of the head before the convex and very prominent eyes. Antennae 11-segmented; pale with the club darker, the club is 4 or 5 segmented, elongate and only weakly differentiated. Pronotum evenly rounded with the basal margin bisinuate and the hind angles acute. Scutellum distinct. Elytral punctation random, quite strong and moderately dense, in many specimens there are larger punctures that form loose longitudinal rows on each elytron.