|Gall (approx 20mm diameter) on a Salix cinerea twig - it has clearly developed on one side of the twig and has a swollen and irregular surface.|
|One side of the gall was softer with fibrous material, possibly the remnants of a galled bud.|
My first stop was the excellent Redfern & Shirley (2011), a standard (and affordable) work with excellent coverage of British galls, though the rapidity of change in cecidology (gall study) means here are always new species being added and new host-galler association being found. It quickly became clear that this is either a species not found in that book, or an unfamiliar form of a gall which is included. Either way, it was time to open the gall and look at the the larvae.
|Larva (approx 12-14 mm long) from the Salix cinerea gall.|
|Larva in dorsal view, noting the paired dots clearest on the front few segments.|
- It could be C. servillana creating an unusual form of gall, or utilising an existing growth of the type sometimes caused by the tree's response to a wound of infection.
- It could be a different species of moth which I can't find reference to or which hasn't been recorded before, at least not as a galler of S. cinerea.
- An unknown gall causer such as that noted on catkins in Redfern & Shirley (2011).I have my money on this option...
- Something I haven't thought of. Also distinctly possible!
- As the larvae are alive, try to raise them as adults and identify the moths that emerge.
- Ask a gall-specialist - in this case I forwarded this post to the British Plant Gall Society.
|The gall is held above the larva which then climbs onto it and begins to investigate the various holes and crevices.|
|The larva continues to explore.|
|After a few minutes, the larva entered the gall - hopefully it will pupate and emerge as an adult.|
Redfern, M. & Shirley, P. (2011). British Plant Galls (2nd ed.). FSC, Shrewsbury.