Notes on Essex specialities. 6: the mining bee Colletes halophilus Verhoeff
Adults are found later than other mainland Colletes species, from mid-August to mid-October,
occasionally into early November, generally in line with the flowering of Sea Aster. The author has
seen females foraging on Picris on a number of occasions, both before the Sea Aster has come into
flower and after it has gone over, and males will certainly forage for nectar on a wider variety of
flowers. Males have been found roosting on grass stems, in much the same manner as males of
Dasypoda altercator (see fig. 2), in groups of up to a dozen (Kirby in Edwards 1997).
Fig. 2. Dasypoda altercator male roosting on stem © P.R. Harvey
Nesting occurs in bare or sparsely vegetated soil, such as that exposed by natural erosion or associated
with rabbit burrows, artificial mounds of soil or sea banks (Falk 1991), and apparently these may be
subject to occasional inundation by the sea (Edwards 1997). At Bradwell one female was found on
1 October 1994 nesting at the edge of a gravelly depression just below the sea wall. At East Tilbury
a nesting aggregation of hundreds of bees occurs in a sandy bank adjacent to the footpath at the end
of the silt lagoons. Here its cleptoparasite, a large variety of Epeolus variegatus (Plate 14 inset),
also occurs in some numbers.
Colletes halophilus has a very restricted distribution in Britain and the species is threatened in
various ways. The grazing of upper Saltmarsh produces grass swards which contain little suitable
forage. Rising sea levels are causing erosion of saltmarshes in Essex and at the present rate most of
the habitat will have been lost within a few decades (Gibson 2000). Managed realignment should
benefit this species at some places on the Essex coast. However, many of the Thames Marshes have
been reclaimed for industrial development, and with the abandonment of older industrial sites next
to the Thames, there is now enormous pressure from initiatives such as the 'Thames Gateway' to
redevelop, often for high value riverside housing. Barking riverside and PFA lagoons and various
sites on the Kent side of the Thames have been lost in recent years and other key Essex Thames-side
sites are threatened.
References
EDWARDS, R.(Ed). (1997) Provisional atlas of the aculeate Hymenoptera of Britain and Ireland (Part 1).
Biological Records Centre.
FALK, S. (1991) A Review of the Scarce and Threatened Bees, Wasps and Ants of Great Britain. NCC.
Peterborough.
GIBSON, C. (2000) The Essex Coast beyond 2000. English Nature.
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Essex Naturalist (New Series) 18 (2001)