Family Cimbicidae - Clubhorn Sawflies
These are large, chunky, sawflies with club-shaped antennae of not more than seven segments. The abdomen is arched dorsally and flattened beneath allowing the abdomen to curl under the thorax. They are fast flying insects and the males of some species are strongly territorial. There are five genera recorded in Britain and three in Ireland. Two genera in Britain, Pseudoclavellaria and Corynis, are known only from a few historic records and are no longer present in Britain. The remaining three genera, Abia, Cimbex and Trichiosoma, fall into two subfamilies: Abiinae and Cimbicinae.
The Abiinae are represented in Britain and Ireland by the genus Abia. Formerly, these were divided into two genera: Abia and Zaraea. However, genetic analysis demonstrates that this split is unwarranted. The species fall in the size range 9 to 12mm. Of the five species within this genus, Abia fasciata is easily recognised as a white banded, black bodied Abia. The remaining four species are more difficult to separate as they are all metallic, bronze bodied sawflies. Antennal colour offers some assistance in that Abia aenea and Abia lonicerae always have entirely black antennae, whereas in Abia sericea and Abia candens the antennae are almost always partially paler.
Larvae of Abia aenea, fasciata and lonicerae feed on shrubby members of the Caprifoliaceae family (e.g. honeysuckles, snowberry and pheasant-berry). Abia sericea and candens feed on herbaceous members of that family (scabious). Larvae cocoon in leaf litter or moss at or just below the soil surface.
The Cimbicinae are represented by the two genera Cimbex and Trichiosoma. Both genera have enlarged mandibles and hind legs which the males use for fighting and defending territory. The species fall in the size range 13 to 28mm.
There have been four Cimbex species in Britain (femoratus, connatus, luteus and quadrimaculatus), though quadrimaculatus is now absent, and only two in Ireland (femoratus and connatus). Of the species in this genus, Cimbex femoratus is the most commonly encountered and in the usual dark form easily recognisable. It is a black bodied sawfly with a cream-coloured membraneous area on the first tergite and with yellow antennae and yellow tarsi. The abdomen is often marked with red, or even predominantly yellow. However, even the palest forms can be recognised by the defined apical banding on the wings. Cimbex connatus and luteus are more difficult to separate and care must be taken in their determination.
Larvae of the Cimbex species feed on birches, alders, poplars and willows.
There are seven species of Trichiosoma in Britain, five of which are also found in Ireland. They are difficult to identify as adults and larval identification often relies on knowing the foodplant that they are feeding on. The adults are all dark brown in colour, with some variation in the tone, and with erect hairs on the abdomen varying in colour and density. Unfortunately, differences in genitalia are also slight and variable. There is not currently a reliable key that incorporates all the species found in Britain and further work is needed to better understand the species boundaries and their ecology.
Larvae of the Trichiosoma species feed on birches, willows, hawthorn and rowans.
Subfamily Abiinae Benson, 1951
Genus Abia Leach, 1817
Abia candens Konow, 1887
Abia nitens (Linnaeus, 1758) =Abia sericea (Linnaeus, 1767)
Abia aenea (Klug, 1820)
Abia fasciata (Linnaeus, 1758)
Abia lonicerae (Linnaeus, 1758)
Subfamily Cimbicinae Curtis, 1825
Genus Cimbex Olivier, 1790
Cimbex connatus (Schrank, 1776)
Cimbex femoratus (Linnaeus, 1758)
Cimbex luteus (Linnaeus, 1758)
Cimbex quadrimaculatus (Müller, 1766)
Tribe Trichiosomini Benson, 1951
Genus Pseudoclavellaria Schulz, 1906
Pseudoclavellaria amerinae (Linnaeus, 1758)
Genus Trichiosoma Leach, 1817
Trichiosoma laterale Leach, 1817
Trichiosoma lucorum (Linnaeus, 1758)
Trichiosoma pusillum Stephens, 1835
Trichiosoma scalesii Leach, 1817
Trichiosoma sorbi Hartig, 1840
Trichiosoma tibiale Stephens, 1835
Trichiosoma vitellina (Linnaeus, 1760)
Subfamily Corynidinae Benson, 1938
Genus Corynis Thunberg, 1789
Corynis crassicornis (Rossi, 1790)
Corynis obscura (Fabricius, 1775)
Benson, R.B., 1952. Handbooks for the Identification of British Insects. Hymenoptera, Symphyta, Vol 6, Section 2(a-c), Royal Entomological Society, London
Liston A, Knight G, Sheppard D, Broad G, Livermore L (2014) Checklist of British and Irish Hymenoptera - Sawflies, ‘Symphyta’. Biodiversity Data Journal 2: e1168. https://doi.org/10.3897/BDJ.2.e1168
Liston, A. D.; Savina, H.; Nagy, Z. T.; Sonet, G.; Boevé, J.-L. 2014: Taxonomy, phylogeny and host plants of some Abia sawflies (Hymenoptera, Cimbicidae). - Zootaxa, Auckland 3821: 125-132
Viitasaari, M. 1989: Taxonomic notes on the genus Trichiosoma Leach (Hymenoptera, Cimbicidae) II. - Annales Entomologici Fennici, Helsinki 55 (3): 111-129