Crabro bipunctatus (ZETTERSTEDT,1838); Lindenius gredleri (KOHL,1878); Crabro nigrinus (HERRICH-SCHÄFFER,1841); Crabro parvulus (PACKARD,1866); Crabro proletarius (MICKEL,1916)
The genus Ectemnius contains some of our larger and more colourful aculeates. All ten British species in this genus have black gasters which are boldly marked with yellow transverse bands or paired lateral spots. Most are locally distributed throughout much of southern England, the number of species and their degree of abundance decreasing northwards. Only three species are known from Ireland (Stelfox, 1927) and a similar number from Scotland.
Ectemnius borealis has the most restricted range of all the British species in the genus, known only from western West Sussex and east Hampshire, north to the Surrey border. The species was first recognised as British in 1972, when a short series was collected on Oxenbourne Down, a reserve of the Hampshire Wildlife Trust, a few kilometres south of Petersfield, Hampshire (Else, 1974; where the species is cited under its junior synonym, E. nigrinus (Herrich-Schäffer)). Further specimens have been encountered there since that year, as well as a nest in a fallen, rotten tree trunk, from which a few individuals were subsequently reared. In 1975 a female was collected in a ride in the adjacent Queen Elizabeth Forest. At the time it was considered that the species may have represented a very recent arrival in England, but this was proved not to be the case as, in 1980, a specimen was shown to G R Else which had been provisionally identified by G M Spooner, on behalf of K M White. The identification was confirmed, and the record was later published (White, 1982). This specimen was collected by K M White from a wooden post near Botley, Hampshire, on 14 June 1938. It was flying with the first-known British specimens of the eumenid wasp Microdynerus exilis (Herrich-Schäffer).