Thereva fulva (Diptera: Therevidae), new to Essex
PETER HARVEY
32 Lodge Lane, Grays, Essex RM16 2YP
The stiletto-flies (Therevidae) have a conical tapering abdomen, a feature found in some other flies
as well. Thereva fulva is a particularly blight tawny species with no conspicuous dark bands across
the abdomen (Fig. 1 and front cover), but Thereva species can be variable and difficult to identify.
Most specimens turn out to be the widespread T. nobilitata.
A single female Thereva fulva was collected at Anchor Field, S. Essex (TQ591778) on 11th June
2003. It was swept from tall grassland with yellow composites (Asteraceae) adjacent to allotment
plots opposite an area of scrub.
The species is listed in Falk (1991) as Nationally rare (RDB3). Most records are from the early part
of this century; it has a well-documented history in northern Kent (Darenth, Foots Cray, Dartford,
Farningham Road Station) between 1868 and 1939, though most of sites involved arc probably
now destroyed. It is also recorded from the south coast of Wales, with isolated records in West
Sussex, West Kent and possibly Gloucestershire (old) and Lincolnshire (1896). More recent records
include 3 sites in Glamorganshire in 1985 and 1986, and Sandwich, Kent in 1975 (Falk op.cit.).
The occurrence of this attractive Hy at Anchor Field is new to Essex. The author has also collected
the species at two sites on the Kent side of the River Thames in recent years, so its occurrence in
south Essex near the Thames is not entirely unexpected. Not so far away across the river in north
Kent, the author collected one female in an area of ruderal lichen heath and scrub at a post-industrial
site on 8th July 1998 adjacent to part of Dartford Heath (TQ517725), and a second specimen was
seen. A further female was collected at the same site in pan traps set between 15th July and 21st July
1998, and another female was collected between 21s1 July and 5lh August 1998. At Littlebrook
Lakes (TQ5576) also in north Kent across the Dartford Crossing, at a highly threatened if not
doomed site, one male was collected in pan traps between 3rd and 10th July 2001. A further female
was taken on 22nd June at the eastern end (TQ5575) and two females in the same area between 3rd
and 10th July. The habitat was a mosaic of drought-stressed grassland and scrub on a substrate of
sand and gravel, exposed at the surface in many places. There were areas of lichen heath, sparsely
vegetated ground, flower-rich areas, taller rough grassland and scrub, with a varied density of trees
close to the fence line. The traps that collected the Thereva fulva were in the open, but close to the
scrub and trees.
Anchor Field lies in a region of south Essex that is geologically complex with a chalk outcrop north
of the Thames variously overlain with sands, and so the vegetation frequently has areas containing
plants normally associated with chalk grassland adjacent to or mixed with areas containing acid
grassland plants. The site overlooks the Thames and runs down from the south-eastern edge of the
Lakeside chalk quarry towards the Thames. It appears to represent a survival of the original south-
facing scarp at the original pre-quarry land level of the chalk and overlying sands. At the southwestern
end there is extensive mature scrub with smaller open areas. The bulk of the site represents grassland,
with allotments, some disused, at the south-eastern end. The site is discussed in more detail in the
article on the spider Ero aphana, new to Essex.
Essex Naturalist (New Series) 21 (2004)
55