Insect portrait – Birch Sawfly

October 1st 2019

This striking insect caught the attention of Charlie Russell on 28th July 2019. It was resting on the deck of his house at Badnaban (NC0721) and photographed on his iPhone.

It is an adult Birch Sawfly Cimbex femoratus and, at some 20mm, one of the largest British sawflies.  Although it looks dangerous, it has no sting, the saw-like appendages of the female being used to insert its eggs into the bark of birch trees.

The pale green larvae hatch in the spring and feed on birch leaves, pupating later inside tough sausage-shaped cocoons anchored to twigs.  The adults emerge in late summer and can be distinguished from other related sawflies by their size, yellow-tipped antennae and the conspicuous white area on the first segment of their abdomens.

Birch Sawflies have been recorded from scattered sites across the British Isles, including the North-West Highlands, and locally from the 10km squares NC02, 12 and 23.

Ian Evans

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Map