The Essex Naturalist
45
HYMENOPTERA
APOCRITA
ACULEATA
CHRYSIDOIDEA
CHRYSIDIDAE - RUBY-TAILED WASPS
Chrysid wasps prey principally on other aculeate Hymenoptera which either
nest in wood or cut stems, or which nest in the ground or build mud cells. The
larva either consumes the host egg or larva and then devours the food provided
for its host (cleptoparasitism), or else it only devours the mature host larva.
Such insects, which hover between true parasitism and predation are referred to
as parasitoids. A great deal remains unknown about chrysid biology and equally,
there is a great deal to be learned of their taxonomy. Within the genus Chrysis
in particular, the validity of the specific status of some taxa is open to question
and a great many collected specimens simply cannot be placed using available
information. Of the 33 currently accepted British species we have records of 18
so far in Essex. Notes on hosts are taken from Morgan (1984).
Cleptes semiauratus (L.) - Notable B
A parasitoid of the sawfly Nematus ribesii (Tenthredinidae).
The only Essex record to date is of a male at the City of London cemetery,
Manor Park on 30th May 1994.
Omalus aeneus Fabr.
A cleptoparasite of sphecid wasps of the subfamily Pemphredoninae.
The only available Essex record is of a female taken at Canfield Hart, neat
Takeley, on 20th August 1986.
O. auratus (L.)
A cleptoparasite of most, perhaps all, Sphecidae that nest in cut stems or dead
wood, such as Pemphredon lethifer, P. inornata, Passaloecus gracilis, Rhopalum
coarctatum and Trypoxylon species.
Evidently widespread in the southern part of the county with records from the
Grays area, Purfleet, Tilbury, Dagenham, Wanstead Flats, Leyton Flats, the
Roding Valley at East Ham and the Limmo Peninsula in the River Lea at
Canning Town. However, it remains unrecorded at present away from this area.
Omalus truncatus (Dahlbom) - RDB 1
Host unknown.
Listed for North Essex prior to the year 1910 in Falk (1991) without further
details.
Hedychridium ardens (Latr. in Coquebert)
A cleptoparasite of Tachysphex pompiliformis.
Evidently common at Colne Point in 1990 (PRH); also recorded at West
Mersea, East Tilbury, Linford Sand Pit and Mill Wood Pit, Grays. Sandy
substrates feature at all sites.