Odynerus simillimus Morawitz, F., 1867, rediscovered in Essex
holes in an area of bare ground at the edge of a footpath. He returned on 7th August to capture one
female. This is in the same general vicinity as the old Harwood records and it seems likely that the
species has remained undetected in the area since that time.
Both authors then visited the site on 10th August. The original aggregation of five nest holes in clay
was found, and although there were no chimneys, a pile of clay pellets was present below each hole.
More aggregations were discovered in a bank beside the road (see photo). Here some holes had
short chimneys but others had none. One nest appeared to have been carefully capped. One aggregation
of thirteen nests was within an area of less than 30cm by 30cm and amongst grass stems. Another
aggregation of seven nests with at least two active nests was in bare clay a metre or so further along
the bank. Further searches in the area revealed one definite nest with a chimney in a rabbit scrape
along the footpath running north along the sea wall and another possible nest was found.
The morning was cloudy and no wasps were seen. The weather improved in the afternoon with
sunny periods developing and becoming warmer. The first active nest discovered had its owner (see
plate 2) leave and return after about 30 minutes, then leave again after short interval inside nest. This
was repeated after about 20 minutes, then another 15 minutes and then more than 30 minutes. A
second active nest was seen, with a wasp which returned, spent a short time inside and then left to
return after about 20 minutes, leaving after a short time inside and not seen again before we left.
Every time the two wasps left they flew across a cornfield towards trees and old gravel pits containing
water. One prey larva was collected from the first returning wasp and the second wasp returned with
same type of larva, held in the jaws behind its head. The larva was about 8mm length with a black
head, two black markings on the first segment, black spines with black spots at bases. The overall
colouration was green, with a pale line at the sides and a wide pale central band. Little appears to be
known about the ecology or prey of O. simillimus, but Richards (1980) describes the prey of the
genus as larvae of Curculionidae (Phytonomus). The identity of the collected larva is in the process
ofinvestigation.
Altogether about 25-30 nests were found, always on sloping clay, not level or vertical and in both
open bare areas and on the ground amongst the bases of grass stems. Four females have definitely
been seen, one captured by David Scott on 7"' August, a second captured by David at the original
aggregation on 10th August and two actively working from nests on the roadside bank. The dates are
likely to be towards the end of the species' flight period; Archer (2000) gives details of two male
records during June and one during July, and one female record during June and one during August.
This is an important discovery of a very rare wasp. The identification of nesting aggregations opens
the door for detailed research into the species' autoecology.
References
ARCHER, M..E. (1989) Odynerus simillimus Morawitz (Hym., Eumenidae) taken in Norfolk.
Entomologist's Monthly Magazine 125: 206.
ARCHER, M.E. (2000) The British Potter and Mason Wasps: a handbook. Vespid Studies, York.
FALK, S. (1991) A review of the scarce and threatened bees, wasps and ants of Great Britain. Research and
survey in nature conservation 35. Nature Conservancy Council.
HARWOOD, B.S. (1902) Aculeates at Colchester in 1902. Entomologist's Monthly Magazine 38: 266-267.
Essex Naturalist (New Series) 18 (2001)
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