Cladius pilicornis - Hairy Knucklehorn

Cladius (Priophorus) pilicornis Curtis, 1833
Priophorus pilicornis (Curtis, 1833)

North to Yorkshire with isolated records to northern Scotland. Seemingly common and widespread (Musgrove, 2024). According to Prous et al, 2019, there is currently no reliable key or species treatment available for this genus. The description follows Benson.

The head on the frons and temples above dull and with minute hair-warts. Cladius pilicornis is a black sawfly with almost white tibiae and tarsi on all legs. The sternopleural region is covered by an unbroken hair-patch. In the male, the third antennal segment has a dentate basal projection on the underside. In the female, the third segment is contracted medially and arched.

Larvae feed on hawthorn.

Jump to other Cladius species

Size: approx. 5 - 7mm

GB IUCN Status: Least Concern
GB Rarity Status: None

Distribution: England, Scotland, Wales, Ireland

Flight period: Bivoltine, May to August

Plant associations: Crataegus spp. (hawthorns)

The National Biodiversity Network records are shown on the map below. (See terms and conditions)

References:

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

Musgrove, A.J. 2024. A review of the status of sawflies of Great Britain - Phase 3: The Tenthredinidae (subfamily Nematinae). Natural England, unpublished

Prous, M., Liston, A., Kramp, K., Savina, H., Vårdal, H. and Taeger, A., 2019. The West Palaearctic genera of Nematinae (Hymenoptera, Tenthredinidae). ZooKeys, 875, p.63.