Taxonomy
Brachyopa insensilis
Distribution
Species Biology
Preferred environment
Both conifer and deciduous forest, over-mature Abies, Quercus and Fagus forest with senescent trees. May also occur in association with old trees in suburban parks. Presence of woodland microclimate seems to be of significance for this insect, since it is not recorded from isolated trees in hedge or pasture. This is an extremely anthropophobic insect in Ireland, not found in the standard Irish farmland landscape of green fields plus hedges, or in conifer plantations, or in suburban gardens.
Adult habitat & habits
Primarily arboreal, but descends to visit sap runs on various trees within woodland and the flowers of certain trees; normally only visits sap-runs when they are in the sun, which tends to be only around mid-day; flies up and down trunks of standing, live trees with a characteristic, rapid, zigzag flight, rarely descending below 3m from the ground. It may occur in small swarms, flying around close to the trunk and some metres from the ground, immediately in front of a sap run (T.Gittings, pers.comm.) - in which circumstance verifiying identity of the species requires climbing the tree!
Flight period
Beginning of May/end June. Larva: described and figured by Rotheray (1991) and figured in colour by Rotheray (1994), Schmid (1996) and Bartsch et al (2009a). The latter authors also provide a coloured photo of the puparium. Larvae occur in sap runs, and less frequently in rot-holes (where internal sap-runs are present?) on the trunks of living deciduous and coniferous trees. The species has been reared from larvae in damp tree-humus in a rot-hole in the trunk of a large, live Acer pseudoplatanus (MS), from sap-runs and goat moth (Cossus) tunnels in Quercus, from behind loose bark, in a pocket of sappy water on the trunk of live Acer monspecellanus (MS), from sap-runs on Aesculus (Sjuts, 2004), Alnus glutinosa (van Steenis et al, 2001) and Abies alba (Schmid and Grossmann, 1996b; Dussaix, 2005a) and Fagus (Krivosheina, 2005). Adults have also been found visiting sap runs on Tilia (Ball and Morris, 2000; T.Gittings, pers.comm.), which probably also provides appropriate conditions for the larvae. Recent literature suggests that B.insensilis is also associated with Ulmus.
Flowers visited
White umbellifers; Photinia, Prunus padus, Sorbus aria.
Irish reference specimens
In the collections of NMI
Determination
See Key provided in StN Keys volume. Kassebeer (2000) does not figure the male terminalia of B.insensilis,referring instead to an illustration provided by Pellmann (1998). The latter figure of the male terminalia of B.insensilis is unfortunately rather misleading in certain particulars and could itself lead to misdeterminations. The appearance of the adult of B.insensilis is shown, in colour, by Torp (1994). The male is figured in colour by Bartsch et al (2009b).
Distribution
World distribution(GBIF)
Denmark south to the Pyrenees and central Spain; Ireland east through central Europe into European parts of Russia and southeast to Tajikistan.
Irish distribution
Added to the Irish list by Chandler (1982). In Ireland, it is probable that the continued survival of this species is largely dependent upon introduced, European deciduous trees, notably sycamore (Acer pseudoplatanus). Sap-runs and tree holes in which sap-runs are present represent a preferred site for larval development of B.insensilis in continental Europe. The potential indigenous Irish tree hosts, oak and elm, are now so scarce in Ireland as overmature trees that overmature sycamore is more frequent and more generally distributed. In this context it is unfortunate that it can be fashionable to remove sycamore from protected sites on the grounds that this tree is not native - it often provides the only remaining refuge for indigenous old forest insects like B.insensilis. This insect is normally found only in the immediate vicinity of the site in which larval development has occurred, which reduces the probability of its discovery. The arboreal habit and short flight season of the adult insect also reduce the susceptibility of this species to collection. Together, these factors combine to suggest B.insensilis is likely to be under-recorded, in comparison with most other syrphids, which needs to be born in mind in considering the status of the species in Ireland. At present, there are but three known records of B.insensilis here, from widely separate locations, and, even if allowances are made for the difficulties of finding this insect, its distribution in Ireland has to be regarded as relictual in character.
Temporal change
Records submitted to Data Centre in 2024
The following map is interactive. If you would prefer to view it full screen then click here.
References
Publications
Speight, M. C. D. (2008) Database of Irish Syrphidae
(Diptera). Irish Wildlife Manuals, No. 36. National Parks and Wildlife Service.
Department of Environment, Heritage and Local Government, Dublin, Ireland.
Speight, M.C.D. (2014) Species accounts of European
Syrphidae (Diptera), 2014. Syrph the Net, the database of European Syrphidae,
vol. 78, 321 pp., Syrph the Net publications, Dublin.