Aprosthema tardum
One of three very similar Aprosthema species found in the British Isles. The separation of the three species has been subject to much study and conjecture over the years. This species is bivoltine and shows seasonal dimorphism adding to the confusion. Head shape differs in that the summer generation has a short head with strongly narrowing temples and longer flagellae, whereas the overwintering spring generation has a longer head with parallel or posteriorly broadening temples and shorter flagellae. Vikberg postulates that the head shape corresponds to the muscle requirements needed for emergence from the cocoon. The summer spun cocoon is weakly formed from soft plant material, whereas the overwintering cocoon (spring generation) is stronger and constructed underground.
A. tardum can be distinguished from Aprosthema fusicorne and melanurum by less erect and more flattened or lateral directed hairs on the mesoscutellum.
Larvae suspected to feed on Lathyrus sylvestris L. For key to species see Vikberg, 2004.
Status: Rare
Distribution: England
Flight period: Bivoltine, May to August
Plant associations: Lathyrus sp. (sylvestris, everlasting sweet pea?)
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
Vikberg, V. (2004). Seasonal head dimorphism and taxonomy of some European species of Aprosthema (Hymenoptera: Symphyta: Argidae). Beiträge zur Entomologie= Contributions to Entomology, 54(1), 107-125