Small World Discoveries

HYMENOPTERA > SYMPHYTA > Argidae > Arginae

One of four virtually identical Arge black-bodied species with darkened wings and black legs.

Although extremely difficult to separate Arge berberidis from the other species, Arge enodis, Arge gracilicornis and Arge nigripes from photos, it may be possible if you can make out the transversely striated tergites or, in the case of females, the characteristic forceps-shaped saw-sheath. Additionally, if it can be seen, there’s an orange-coloured protrusion at the apex of the abdomen, which is regarded as being unique to the species.

Notwithstanding the above, and accepting the fact that accurate identification can only be determined from microscopic examination, Arge berberidis is by far the more commonly recorded of the four species and, as such, seems the most likely candidate.

Arge nigripes, the Black Rose Fusehorn, is the most widespread of the other three species. It lacks the previously described characteristics of Arge berberidis and doesn’t have a hair fringe at the wing tips like Arge gracilicornis. Recording is always a problem with very similar species and that could well be the case here, both with Arge gracilicornis, and Arge enodis that appears to be rare.

Whereas the larvae of Arge berberidis are associated with berberis and mahonia plant species, Arge nigripes, as its common name suggests, feed on the foliage of roses. The caterpillar-like larvae of the species are green with two pale stripes down the back and a pale brown head, but without conspicuous dark spots on the body as the two more well-known rose-feeding species Arge ochropus and Arge pagana.

The adults of Arge berberidis may be seen from May through to October, whereas Arge nigripes are unlikely to be encountered much beyond the end of July, which is another pointer to identification of species seen later in the season.