Didea alneti (Fallén, 1817)Biology
The larva is aphidophagous and usually associated with conifers, although it has also been found feeding on other arboreal aphids such as those on Sallow Salix and Lachnus sp. on Oak Quercus. Adults occur in or near woodland, including conifer plantations where they are primarily arboreal, but will descend to visit flowers.Distribution
This species has an unusual distribution, with a several widely separated areas producing a number of records over a period of a few years (e.g. Forest of Dean in the 1890s, Sutton Park around the turn of the century, Speyside area in 1930s) followed by apparent local extinction. This pattern suggests an occasional migrant or vagrant (or accidental import?) that sometimes establishes temporary populations. The only recent records come from Slaley Forest, a large conifer plantation in southern Northumberland, where it was found twice in 1989.Status
Listed as "Endangered (RDB1)" by Falk, 1991 and Shirt, 1987, but dropped from this status by Ball & Morris, 2010 who consider it to be a vagrant prone to occasional erruptions during which it manages to establish short lived colonies.