Sawfly

Large Rose Sawfly larvae (Arge pagana)

While checking over a corner of the garden for potential new denizens recently, I came across these orange-headed "caterpillars", munching enthusiastically on a rose leaf. Some internet research on Mike's part eventually attached a name: they're Large Rose Sawfly larvae. This is one of two sawfly species that attack roses in the UK. The larvae of the other species (the Rose Sawfly, Arge ochropus) are very similar. The big difference is that larvae of this species have pale hairs on their heads, while those of the Rose Sawfly have dark hairs. (You'll have to click on the picture above to see any trace of those hairs — or rather, the lack of dark ones.) In addition, the spot at the end of their abdomen is solid black; those of the Rose Sawfly have a pale centre. Adults are about 10 mm (4/10 of an inch) long. They're black on the thorax and orange on the abdomen, and have dark, tinted wings and black legs (many with some orange on the femur of their hind legs).

Sawflies are related to bees, wasps and ants. Unlike bees and wasps, they lack stingers. They're named for the distinctive ovipositor of the female. These egg-laying appendages have sawtooth edges, which allows the females to saw into plant stems to lay their eggs. Larvae often hang out together (as ours did), particularly while they're younger. They'll overwinter as pupa, to emerge as adults in the spring. Adults are primarily seen from March (in more temperate years) to June. The species is common throughout the UK, and found across the Palearctic to the Pacific Ocean. If they eat all of "our" roses (planted by the previous owners), we won't be upset. Neither of us are particularly fond of plants that bite back!

In defensive posture