Sawfly surprise

Byfield Pocket Park again. Well, you never quite know what will turn up.


For those not familiar with sawflies, they are hymenoptera and thus related to bees, wasps and ants. And they are difficult! No concise book exists on the identification of the British species and students of these often common insects depend on consulting a range of books, articles and the examination of reliable labelled collections for the accurate naming of specimens. I generally ignore them and set them free if any find their way into my sweep net.


Fortunately some are common, widespread and easily recognised, so when I found a group of their caterpillar-like larvae in their characteristic pose on a birch sapling I recognised them immediately as Birch Sawflies, Cimbex femoratus. Except that when I got home I realised I was quite wrong.


I hadn't even bothered to take a specimen but fortunately I'd taken a number of not-very-good photographs. As explained, sawflies are not my thing but as soon as I examined the photographs I realised that my original assumption had been unforgivably hasty. So what was it?

The caterpillars of Pristiphora testacea in a characteristic pose.

Byfield Pocket Park. 27 August, 2020

After trawling through a couple of books and web sites without success It became clear that it wasn't a common or garden species. Fortunately I knew the foodplant so that narrowed things down considerably. Any road, as my mother would say, six books later I did eventually identify it as Pristiphora testacea. An examination of the N.B.N.(National Biodiversity Network) maps on-line showed only eleven records for the species in Britain but unfortunately these maps rely on records being submitted - and not all are. Nevertheless, this seems to be a genuinely scarce species.

What else? Yellow Toadflax, Linaria vulgaris was present in a neglected flower bed. It is common of course but is a cheerful little plant, much visited by bees and a new species for the site.

Yellow, or Common. Toadflax. Byfield Pocket Park. 27 August, 2020

Greater Plantain, Plantago major, was also new but of more interest was the mine of a fly, Phytomyza plantaginis, on its leaves.

Phytomyza plantaginis seems to feed on any plantain species.

Byfield Pocket Park. 27 August, 2020

And now to go through all the other insects found during my visit. More surprises perhaps?