112
The adult wasp is distinguished by having the mesoplcuron entirely reticulate, the median scutal
furrow present in the posterior third, scutellar foveae weakly or indistinctly separated and closed
externally and the length of the radial cell is 2'/3 x width.
Phanacis centaureae Foerster, 1860 1 km.sq. records: 5
Host Plant: Centaurea scabiosa L., Greater knapweed
Part galled: flower stem
Scarce
Phanacis centaureae
First recorded as a gall in the north-west of

the county in a disused chalk pit at
Arkesden in 1992, further examples being
found on roadside verges in the area. A
search at Grays located the species on a
steep chalk bank in 1996. The only
localities not situated on the chalk are at
Glemsford Pits and Valley Walk, Borley.
This species is restricted by the distribution
of its host plant and perhaps needs a
reasonable stand of Greater knapweed to
maintain a viable population. It is again
likely to be under-recorded, as the galls are
internal in the stem as in the preceding
species. Occasionally, a slight swelling is
discernable in some galled stems.
The adull insect is separated from all other Phanacis spp. by liaving the marginal vein
completely pigmented and in the female, the third antennal segment is l'/2 x the length of the
fourth. In both sexes the mesoscutum is reticulate and the scutellar foveae confluent, forming a
broad hollow, open externally. Radial cell length 2'/2 x width.
Phanacis hypochoeridis (Kieffer, 1887) lkm.sq. records: 28 Local Fig. 1
Host plant: Hypochoeris radicata L., Cat's ear
Part galled: flower stem
The first Essex record fortius species appears to be from Epping Forest in 1933 (Burkhill,
1934). Niblett (1950) gives a record from Benfleet and there is a specimen from Elmstead
Market, collected by K.Hawkins in 1982, in the collections of Colchester Museums. It is now-
known to be fairly widespread, with a recording bias to the north-east of the county.
A variety of grassland habitats together with scrub are utilized, but these must be either
unmanaged or cut late in the season. The eggs are laid in the stalk of the inflorescence in early
summer and premature cutting, severing the source of nutrients before a critical gall size is
reached, appears to be fatal. Cutting in late summer when the gall has finished its development
appears not to be detrimental, however. Under normal conditions the galled inflorescence
remains attached to the plant until spring.
Essex Naturalist (New Series) 16 (1999)