Large Rose Sawfly - Arge pagana

Description

Arge pagana is up to 10mm, with an orange abdomen and black sides to the thorax. Because of the dark, tinted wings, which are kept over the abdomen, the orange colour may not always be clearly visible. The legs are mainly black as well, with some orange on the hind leg femur. Like all species in the Arge genus, the antennae have only 3 or 4 segments, with the end segment being very long.

Similar Species

The only other orange bodied Arge with a dark intercostal on the wings is Arge ochropus and this species has 'stripy socks'.

Larvae of Arge ochropus and Arge pagana are tricky to separate, especially from photos. The best feature to check are the fine hairs on the head, which are dark in ochropus and pale at the tips in pagana. The black marking on the last dorsal segment can also be useful – this is a simple spot in pagana but more-or-less indented with a pale middle in ochropus. In the field the best way is to look for the egg scars on the main stem near where the larvae are feeding – two parallel rows in pagana and just a single row in ochropus.

Identification difficulty
ID guidance
  • long final antennal segment
  • orange abdomen
  • thorax sides = black
  • intercostal space = black (leading edge of wing)
Recording advice

Check it has a long final antennal segment, a yellow abdomen, black sides to the thorax and a dark intercostal space.

Habitat

Hedgerows and gardens, especially where rose species are present.

When to see it

March to June

Life History

Like all sawflies, female Large Rose Sawflies are in possession of a little saw. With it they make parallel cuts in the fresh shoots of the host plant. In the cut a bunch of eggs is deposited. The larvae hatch quite quickly and move in a group to the freshly emerged leaves. The young larvae (yellow with black spots) stay together for quite some time, capable of eating the entire shoot. Older larvae lead a more single life and eat from older leaves as well.

UK Status

The Large Rose Sawfly is a common species all over Britain, although most records come from the south of England.

VC55 Status

Common in Leicestershire and Rutland.

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Leicestershire & Rutland Map

MAP KEY:

Yellow squares = NBN records (all known data)
Coloured circles = NatureSpot records: 2020+ | 2015-2019 | pre-2015

UK Map