Taxonomy

Chrysotoxum cautum

Distribution

Species Biology

Preferred environment

Deciduous forest and scrub; unimproved grassland and lightly grazed grassland which has not been subject to ploughing or tillage. The single Irish specimen was apparently obtained from an area of estate parkland. It is characteristically a species of open, grassy areas in forest, both deciduous and coniferous, and unimproved, humid, but well-drained, grassland.

Adult habitat & habits

Open areas in forest or scrub on well-drained sites; clearings, tracksides etc.; usually flies within 2m from the ground; settles on foliage of bushes etc.

Flight period

May/July, plus April in southern Europe. Larva: undescribed. Egg: the morphology of the egg of this species is described by Chandler (1968). The morphology of the chorion of the egg is figured by Kuznetzov (1988). The female has been observed ovipositing on roadside grasses by Reemer and Goudsmits (2004) and on grasses and Galium at the edge of a Rubus thicket by Smith (2004). The eggs are apparently laid singly.

Flowers visited

White umbellifers; yellow composites; Allium ursinum, Caltha, Cornus, Crataegus, Euphorbia, Geranium, Plantago, Ranunculus, Rhamnus catharticus, Rubus, Sorbus aucuparia.

Irish reference specimens

In the collections of UM

Determination

van der Goot (1981). The female of this species is unique among European Chrysotoxum in possessing a longitudinal, median, membranous strip on abdominal tergite 6, which effectively divides this tergite into two parts. The male terminalia are illustrated by Lehrer (1971). The adult insect is figured in colour by Kormann (1988), Stubbs and Falk (1983) and Torp (1994).

Distribution

World distribution(GBIF)

Finland south to the Pyrenees and Spain; Ireland (extinct?) and Britain (southern England) eastwards through central and southern Europe (Italy, the former Yugoslavia, Bulgaria, Greece) into Turkey and Russia as far as the Altai mountains (Mongolia). C. cautum reaches its northern limit in Europe at the southern tip of Norway. Further south it becomes frequent and widely distributed in Atlantic and central parts of Europe, extending beyond Europe southwards into Turkey and eastwards to Mongolia.

Irish distribution

Added to the Irish list by Speight and Nash (1993), on the basis of a solitary specimen collected in 1919. If C. cautum is not rediscovered in Ireland, inclusion of this species on the Irish list may require reconsideration. This large and distinctive species would seem to either be extinct in Ireland, or to have been recorded here in error. But in case it does persist in the island it should be included in any listing of insects requiring protection at national level. 

Temporal change

Records submitted to Data Centre in 2022

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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.

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