Sympherobius pellucidus

Four of the five British Sympherobius species have been found in Norfolk so far but none of them have been recorded more than half a dozen times up to 2025. However, as I've recorded 11 individuals covering all four species in unremarkable habitat here in North Elmham, I think they must be vastly under-recorded.

Most members of the genus tend to be rather dark brown and thus can recall the spongeflies (family Sisyridae). They can be distinguished from spongeflies by the presence of a recurrent humeral vein and the presence of forks in many of the veins along the front margin of the wing. From other genera of brown lacewings they are best differentiated by having fewer cross-veins in the hindwing (specifically, according to Plant (1997), none in the outer third of the hind wing OR no more than 4 altogether) - of course this is very hard to see on a live insect and unlikely to be evident from photos.

Like Sympherobius fuscescens and Sympherobius klapaleki, but unlike the other species in the genus, pellucidus has three branches to the radial sector of the forewing - the others have two. Unlike fuscescens, there is distinct darkening around the cross-veins of the forewing, however on the one I caught this wasn't obvious and had to be looked for quite carefully, although it was apparent in the photos of the live insect. Note that although Plant says that fuscescens has no darkening around the cross-veins, a tiny amount of darkening may be visible on very close scrutiny - however it is certainly not distinct and in my experience was not apparent in photos of the live insect. Sympherobius klapaleki is similar but has contrastingly pale yellow-brown first and second segments of the antennae. Identification of males is best confirmed by examining the tip of the abdomen (again, see Plant for diagrams).

At the time of writing this is Norfolk's only record of pellucidus.

male Sympherobius pellucidus showing forewing (whole wing and close-up to show the darkening around the cross-veins) and abdomen tip, North Elmham (Norfolk, UK), 29th May 2019