Identification: Elongate black shining fly with orange legs. The swollen hind femur has a row of spines beneath. Distinctive patch of white hairs on the occiput behind the eyes.
Roháček, 2012: It is a distinctive, medium-sized (6.0-9.0 mm), elongate, shining black fly with reddish femora and hind femur strikingly swollen and ventrally spinose.
I have observed this species on a couple of occasions. At first glance it appears and moves like a dark ichneumon, weaving through brambles and not resting long. Locating likely ovipositing sites and staking those out might prove a good tactic.
UK - Falk, Ismay & Chandler, 2016: pNationally scarce
The clearance of broad-leaved woodland for agriculture, intensive forestry, urbanisation etc. and the removal of dead wood and old or diseased trees.
Oldroyd, 1970: Hind femora swollen, with two ventral rows of spines. Abdomen long, with a narrow waist. Cup relatively long and parallel sided. Anal vein (A1) almost or quite reaching the wing margin.
Colyer & Hammond, 1951: Medium-sized fly superficially like Loxocera (Psiilidae); 3rd antennal segment short and rounded; hind femora with double row of short ventral spines; wings narrow; alula absent; costa unbroken; Sc visible throughout and gently curved; apex well-separated from apex of vein R1; abdomen greatly elongated and attenuated; ovipositor short, retractile.
Roháček 2012: The larvae live under the bark of dead or dying deciduous trees and are predatory or necrophagous on the larvae of other subcorticolous insects (Krivosheina & Mamaev 1967). The adults can be found in woodland areas, usually near the breeding sites of the larvae, on tree trunks and leaves.
Falk, Ismay & Chandler, 2016: The larvae develop beneath the bark of dead broad-leaved wood and in Britain the puparium has been found beneath the bark of a dead Oak (Quercus), although adults have been found in association with the dead wood of Aspen (Populus tremula) on the continent. Krivosheina & Krivosheina (1997) described the larva from material found under Poplar (Populus species) and Aspen bark in Russia. It has also been reared from beneath the bark of Small-leaved Lime (Tilia cordata) (Derek Lott’s record, A Godfrey pers. comm)
Larvae & pupae under the bark of aspen, willow & poplar (Krivosheina, N. P., & Krivosheina, M. G. (1997))
Krivosheina, N. P., & Krivosheina, M. G. (1997). A contribution to the biology and morphology of the larvae of Megamerinidae (Diptera). Studia Dipterologica, 4(1), 231–237.
Full morphology of larvae