Cacopsylla ambigua

Previously known as Psylla ambigua but now placed in the genus Cacopsylla.

This was swept from willow. It keyed straightforwardly to ambigua, was on the correct foodplant and the genal cones and terminalia compared well with the diagrams in the RES key. The wing spiculation is so faint and dense that I could only just see it under the dissecting microscope - the compound microscope providing a better view. The forewings were 2.8mm long.

female Cacopsylla ambigua showing forewing (with close-ups under both microscopes), genal cones and terminalia, North Elmham railway (Norfolk, UK), 2nd May 2026

I had previously found an insect which had keyed to Cacopsylly ambigua and I had featured it here on this page. The wing membrane was clear and the spiculation went right up to the veins, however I noted that the terminalia were a little on the short side and the genal cones were not exactly as shown in the key for ambigua. After finding the individual above and comparing the terminalia with the original one, it became clear that they were not the same species - the terminalia were much longer on the first individual, so the first one could not be ambigua as originally suspected. After discussion with James Emerson, we concluded that the first one must be a teneral Chamaepsylla hartigii. Although its wing membranes were clear unlike non-teneral individuals of that species, the veins were more coloured than shown by this ambigua.