B. cryptarum is hard to recognise and has been regarded as a valid species only recently - and then not by everyone. This explains why it has been explicitly dealt with in rather few articles.
For Rasmont (1984), B. cryptarum is a rather continental species. It has been found as far east as the Ussuri (E. Siberia) (Rasmont et al., 1986). In the west, it is absent from the Pyrenees and the Iberian and Italian Peninsulas. It has been found only recently in the British Isles and in Ireland. Along the Atlantic coast, B. cryptarum often coexist with B. magnus, both species being difficult to separate. North of the 45th parallel, populations live in the plains, mainly in the Ericaceae heather ; more south, it is a mountain species.
Concerning N. Europe, few ecological data are available. The species may exist up to the north of Fennoscandia. According to Pamilo et al. (1997) and to many personal observations, B. cryptarum may totally supplant B. lucorum north of the Arctic Circle.
P. Rasmont