Orange Bibio Bibio hortulanus

Males are black and therefore similar to most other Bibio species but females are much more distinctive - although care needs to be taken to eliminate Downland Bibio Bibio anglicus.

Steven Falk lists 3 characters differentiating hortulanus from anglicus. 1) Size - wing length of anglicus is up to 7mm compared with up to 9.5mm for hortulanus (this one was 8mm). 2) Longer basal section to vein R4+5 on hortulanus cf. anglicus. I wasn't entirely sure which vein (or bit of vein) this referred and various wing-venation diagrams didn't convincingly answer this, but I think it's the vein crossing through the mid-toned shaded section in the wing shown below, between the dark shaded cells against the costa and the unshaded cells below. At least this is similar in Steven's photos of hortulanus and shorter in his photos of angicus. 3) Costal area much darker than the rest of the wing in hortulanus vs. wing membrane uniformly dark in anglicus. I found this confusing as Steven's photos of both species showed a clearly darker costal area and the majority of the wing appearing pale, however perhaps if you were to examine the wings in life the difference might be clearer than comes across on photos? Perhaps easier to see is that whilst the cells right along the costa (costal and subcostal?) appear predominantly dark on both species, on hortulanus only (at least in Steven's photos and also in mine) the remainder of these cells and most of the next closed cell towards the middle of the wing (I'm not quite sure if this is a radial cell or the first basal cell?) is shaded darker than the remainder of the wing.

female Orange Bibio Bibio hortulanus showing wing, Dillington Carr (Norfolk, UK), 1st May 2022