On Bourletiella (Cassagnaudiella) pruinosa (Tullberg, 1871) and its allies (Collembola: Sminthuridae)

In dry dune vegetations in the Netherlands a species of Bourletiella occurs that is closely related to B. pistillum Gisin, 1946, and B. radula Gisin, 1946. The species is characterized by a virtually obligatory sexual neutralisation of all males throughout the summer. A study of type material proved the identity of this species with Bourletiella pruinosa (Tullberg, 1871). A lectotype is selected for B. pruinosa as well as for B. agreni Stach, 1956. B. agreni, created for B. pruinosa sensu Ågren, 1903, Linnaniemi, 1912, is proved to be a junior synonym of B. pistillum. B. pistillum incisa n. ssp. is described from the Pyrenees and the Ardennes. Bourletiella cruciata Haybach, 1972, is shown to be a sexually neutralized form of B. pistillum, and is a junior synonym of the latter. Herewith the occurrence of sexual neutralization is established in B. pistillum. For B. pruinosa (type-species), pistillum and radula the new subgenus Cassagnaudiella is proposed.