The Scapa Flow Landscape Partnership Scheme

Sawflies

Sawflies are not in fact flies, but closely related to bees, ants and wasps. They are the most primitive members of the insect order Hymenoptera. Their name is a reference to the egg-laying tool of the female which is used to cut slits in plants and leaves in which to lay eggs. Sawflies do not sting. As a group, sawflies are very often overlooked in favour of their more familiar relatives.

Recognising sawflies

Adult sawflies resemble flying ants, but without the 'waist' and with a fly-like head. Many are a dull brown or black in colour, but some are bright green or have a black and yellow pattern like wasps. They range in size from 1-3 centimetres. Orkney's largest species, the birch sawfly, Cimbex femoratus, is about the size of a bumblebee.

Lifecycle
The larvae of sawflies are caterpillar-like but with legs on nearly all segments. They feed gregariously on plants and some species can be pests. A few species are gall makers. When disturbed the larvae adopt an S-shaped pose, raising their rear ends and waving them about. This helps to ward off predators. Sawfly larvae are an important component in the diet of some Orkney birds, such as chiffchaffs. When fully grown, the larvae pupate in the ground with adults emerging the following spring. The adult insect feeds on pollen and nectar, and sometimes other flower-visiting insects. The lifespan of the adult ranges from a few days for some species to about four weeks.
 

Larva - Sawfly larvae look similar to moth and butterfly caterpillars.

 

Adult - The green colour of Rhogogaster viridis acts as camouflage.

 

Habitat

There are around 500 species of sawfly in Britain, and at least 40 are found in Orkney. They are commonly seen on flower heads during warm spring and summer days. Many can be found in tall grassland or scrub. Around Scapa Flow look for them on umbellifers and heather in sheltered areas, along the edges of streams, or in roadside verges.

Jenni Stockan
Insect Ecologist
The James Hutton Institute
Craigiebuckler
ABERDEEN AB15 8QH