HYMENOPTERA > APOCRITA | Parasitica > Cynipoidea > Cynipidae

There are currently around 90 recognised species of cynipid wasps on the British List, which are placed in 22 genera, separated into eight distinct tribes (as confirmed below). Although the majority of these species are gall-inducers, the family also includes some inquilines that have to adopt an alternative strategy as they are unable to initiate their own gall. The end result is much the same, as the larval stages of all cynipid wasps develop inside the protective case of a plant gall, but it's important to understand the different methods.  

The gall-inducing species are mostly host-plant specific, primarily of oaks, but also roses and certain herbaceous plants. The female wasp lays her eggs on receptive tissue, which starts a process that results in the gradual growth of an abnormal structure that we know as a gall. This foreign organism damages the plant, but certainly doesn't kill it, so in essence these particular species are parasitic wasps, not parasitoids. The galls vary from species to species with different structures, shapes and colours. Given that the adult wasps are rarely seen, the primary interest in this family is with the galls that, in most cases, can be easily identified from various guides and internet resources, such as The British Plant Gall Society. If you can confidently identify the gall, you have effectively confirmed the wasp species.

Inquilines, on the other hand, inject their eggs into a pre-existing gall that's in the early stage of development. The process changes the natural morphology in favour of the inquiline which, one way or the other, usually results in the host larvae dying, typically through starvation or sometimes by being eaten. Whereas the true gall-inducing species form distinctive galls of their own making as previously described, inquilines ('temporary residents' from the Latin inquilinus) end up modifying the shape of the host gall as it will now contain the original egg chamber as well as a new chamber that is formed when the inquiline egg is injected. Initially the two developing larvae battle for space as the chambers grow, but eventually the parasitoid larva of the inquiline will take over even if the host is another cynipid. In these situations, it's impossible to know the species that will emerge.

For future reference, I thought it would be useful to have a list of the tribes, related genera and numbers of species, together with a few notes about their biology. I also looked at the records on the NBN Atlas and other sites, such as NatureSpot, so that I could come up with a list of species that are likely to be seen. As far as I can tell, the vast majority of records are of the gall rather than the actual wasp as expected, although I'm sure there are a few where an actual specimen has been reared and/or properly identified.

It's obviously been cobbled together from various bits of information, but I think it's pretty accurate.

Aulacideini - gall-inducers on various herbaceous plants

Aulacidea (6), Isocolus (3) and Liposthenes (1), although only three species are likely:

Aulacidea hieracii on hawkweed [Hieracium], Isocolus scabiosae on knapweed [Centaurea] and Liposthenes glechomae on ground-ivy [Glechomae]

Aylacini - gall-inducers on Poppies [Papaveraceae]

Aylax (2) - very rarely recorded

Ceroptresini - inquiline on Cynipini Oak galls

Ceroptres (1) - Ceroptres clavicornis, which has only been officially recorded once in past 20+ years

Cynipini - gall-inducers on Oaks [Quercus], and occasionally on Beeches [Fagus]

Andricus (c.28), Aphelonyx (1), Biorhiza (1), Callirhytis (2), Cynips (5) and Neuroterus (6), Plagiotrochus (1),

Pseudoneuroterus (1) and Trigonaspis (1) - discussed an/or featured on the next page

Diastrophini - gall-inducers on Rosaceae [Rubus and Potentilla], and inquiline on Rosaceae [Rubus and Rosa]

Diastrophus (1), Periclistus (3) and Xestophanes (2)

Diastrophus rubi - well recorded on Bramble [Rubus], Potentilla - records for Potentilla x | Hybrid Potentillas!

Xestrophanes brevitarsis on Tormentil, and Xestophanes potentillae on Creeping Cinquefoil [Potentilla]

Diplolepidini - gall-inducers on Roses [Rosaceae]

Diplolepis (5): Diplolepis rosae - regularly recorded, Diplolepis nervosa - well recorded, Diplolepis eglanteriae (sometimes agg.) and Diplolepis spinosissimae - occasionally recorded

Phanacidini - gall-inducers on herbaceous plants [Asteraceae and Lamiaceae]

Phanacis (3), Timaspis (1) - Phanacis hypochoeridis elongated swelling in Cat's-ear [Hypochaeris radicata]

Synergini - inquilines, primarily on Cynipini Oak galls, although some may be gall-inducers?

Saphonecrus (1), Synergus (14) - Synergus albipes, Synergus gallaepomiformis and Synergus reinhardi are occasionally recorded, presumably as adults that have been properly examined

Excluding members of the Cynipini tribe, it looks to me that the most likely species to be found - in terms of the gall - are the four common Diplolepis gall-inducers on Roses, Diastrophus rubi on Bramble, and probably the Aulacidea and Xestrophanes species on their various host plants.

Frustratingly, even if you manage to photograph an adult, they are extremely difficult to identify without close inspection and, in most cases, will just end up as a representative species. They're quite variable, but generally small, no more than 5mm or so, usually shiny brown or black with a humped thorax. The abdomen is compressed with only two segments visible from above as the remainder are telescoped beneath; the first segment of the hind tarsi is about as long as the others combined; the antennae are filiform with 13-16 segments; and the wing venation is reduced to the anterior portion and lacking a stigma.

I haven't, as yet, been out specifically looking for galls, but I have photographed a few, so I've added this page for photos of any adults I'm able to find, and have retained the original page purely for Cynipini oak galls. I may need to include a further page at some point if I'm able to include photos of any of the other galls.

Three different individuals are featured below. The first was photographed in our back garden a few years ago. It wasn't on an oak, but we do have oak trees in the very near vicinity. It was identified as the Knopper Gall Wasp [Andricus quercuscalicis] and I have no reason to doubt that assessment. The other two were found at the same location in the New Forest a couple of months apart - one on moss, the other on fungi. The site is a patch of open woodland with mainly Beech, but also some Oak trees. Consequently, I would guess that they're both members of the Cynipini tribe, but that's purely an assumption.

Please note that the original (now updated) page that features some of the galls that I've photographed can only be accessed from this link or via the associated thumbnail image on the Parasitic Wasps home page, as it is not in this collection and, consequently, is not the next page in this sequence.

New page added, March 25 (v.1)