Brachyopa pilosa

Brachyopa pilosa Collin, 1939

Nomenclature:

Prior to 1939 the only listed British species was B. bicolor. The additional species were not covered by a widely available key until Coe (1953). Consequently, records prior to 1953 must be based on verifiable specimens.

Biology & ecology:

The larva filter feeds on microbes in sap runs. Adults fly from April to July in the vicinity of distinct sap runs on trunks or cut stumps. They may also be found on exposed trunks up until the point where fermenting sap has dried up and the bark becomes cracked and desiccated. Oak Quercus sp. and Beech Fagus sylvatica are preferred in southern England, but adults have been noted in association with fallen White or Grey Poplar Populus sp., stacked logs of Aspen Populus tremula and Birch Betula sp. It breeds in sap runs on Aspen in Scotland.

Distribution:

There are two distinct populations; one in southern England that reaches as far north as Stoke on Trent, and west to south Wales; the other is centred upon the Moray Firth. Recent increases in records may be indicative of a northward expansion of the range of the southern population.

Status & conservation:

There seems to have been a decline in occurrence over the past 35 years, but with a recent up-turn. It will be interesting to see whether this is maintained. Rare (RDB3) according to Shirt (1987), revised to Notable by Falk (1991) and LOWER RISK (Nationally Scarce) by Ball & Morris (2014).

Recorded from 64 hectads since 1990.