I am getting slightly hooked on sawflies – a difficult task as there are hundreds of look-alike species, some are very tiny, and there is no handy guide book. Even worse some of the identification criteria are tricky – impossible-to-see things like the claws on the back legs, or shape of the ovipositor (which in live insects is tucked away most of the time). Even the massive and extremely useful websites Naturespot and Eakrings Birds aren’t all that helpful when it comes to IDing sawflies…and to be honest I’m not sure I’d ever positively identified one before this spring.
However, there is help at hand in the shape of the Sawfly yahoo group which like so many Yahoo enthusiast groups is watched over by some top-rank experts (in this case including Andrew Halstead of the Royal Horticultural Society and John Grearson who is Wiltshire’s County Recorder). Queries submitted are answered with patience and authority, where ID is impossible it’s so stated, and observers are reminded that sawflies are a very under-recorded group and every record is potentially useful in helping understand UK sawfly distribution.
Take the rather pretty (these things are very subjective I appreciate) lime-green banded sawfly I found drowned in a teasel ‘water tank’ yesterday (teasels often hold water where the leaves join the stem – a useful adaptation for dry periods as the plant often grows in arid sites with little ground water retention). A search of Google images brought me eventually to the North American species, Wheat Stem Sawfly Cephus cinctus. John Grearson responded to an ID request saying that it was a Cephus, one of the stem sawflies, and “either Cephus spinipes (formerly C. cultratus) or C. pygmeus. If you have kept the specimen have a look at the tarsal claws. In spinipes the inner claw is short and erect well away from the apex. In pygmeus the inner claw is more or less parallel with the apical one.”
Unfortunately the one I had was a little bit soggy and disintegrating in that decisive way that insects do after being immersed in stagnant water overnight. I didn’t have it to hand, in other words, by the time I knew what to look for. It will forever have to go down as an either/or…
More definite and easy to ID is the ‘pear slug’ in the photo below (once you know that’s it’s not a ‘slug’ but a sawfly larva anyway). The only dark UK ‘pear slug’ is Calora cerasi, the larval stage of the Pear Sawfly, which characteristically removes the upper layers of the leaf as shown. I’d actually been looking out for this larva, as we have an ancient pear tree in the front garden that should attract any adults in the area. I’ve yet to see an adult, incidentally but the photos are proof positive that they’ve been here lately! If you’ve got a fruit tree that has ting strips taken out of some of the leaves it’s worth checking for a similar smudge of slime that in fact could well be this species.
All photos copyright Charlie Moores/Talking Naturally 2012