500 British species, although there are no native saw flies in New Zealand.
The saw fly fossil record stretches back 180 million years to specimens found in what is now Russia and Australia.
They are considered to be the most "primitive" of the Hymenoptera.
Adult saw flies
The adults have simple mouthparts with well-developed jaws and feed mainly on pollen (see the photograph below) which they grind up, although some adults are partly carnivorous. They favour open type flowers with large inflorescences of white or yellow.
They got the name saw fly because most of the females have an ovipostior that has visible saw-like teeth (see the photograph and drawing below). The female uses this to cut slits in plant stems and leaves, then she lays her eggs in the slit.
Saw flies do not have a sting.
The sawfly on the right is Rhogogaster viridis in the Tenthredinidae family which has 900 European species, and almost 400 species in Britain.
In this species the pterostigma on the front edge of the forewing is either all green or all yellow, and you can just make this out as she has not completely closed her wings. Adults of this species fly from may to August and are 10 - 13 mm long. The head and thorax are green with black markings.
The larvae eat a wide variety of leaves, and is green, grey or yellow with black spots along the sides. It is found on willow, poplar, alder spirea. It is found in forest edges and clearings.