4
up, then overtake. Because the character of Aspen growth has changed little more growth
occurs.
The critical factor seems to be the presence of shade to keep drawing the Aspen trees
upwards which they seem unable to do on their own. A feature of these stands is the fact
that all the trees are growing at an angle away from the shading tree.
David Bloomfield
A BEE AND SPIDER-HUNTING WASP NEW TO ESSEX
On the 21st April this year Colin Plant, Peter Yeo and myself visited an area near the
Essex/Suffolk border south of Glemsford. There is a section of old disused railway track
adjacent to old sand and gravel pits with areas of sallow, sedge marsh, sandy banks and
lichen heath. We all took males (determined later) of the Nationally Endangered (RDB1)
cuckoo bee Nomada xanthosticta, a cleptoparasite of the spring mining bee Andrena
praecox. The Nomadas were flying in numbers around the bottom of a sallow bush at the
edge of an area of lichen heath. The host bee was present in small numbers, collecting
pollen from the sallow catkins.
On a further visit the following weekend I found the male Nomadas present in
considerable numbers flying around the bottom of sallow bushes at a number of places on
the edge of the lichen heath. Several females were found flying along a north-facing
bank between the lichen heath and the old railway track where the host bee seemed to be
nesting. Spider hunting wasps were active and several males were collected. These later
proved to be the widespread species Priocnemis perturbator together with two males of
the Nationally Scarce (Notable A) species Priocnemis coriacea, apparently new to Essex.
The Essex Spider Group has visited the site on several occasions to record spiders and it
is known to have a diverse and interesting fauna. The section of old railway track is
home to the only known Essex colony of the Nationally Rare (RDB3) bee Andrena
hattorfiana which has an obligate association with scabious, usually Field Scabious
Knautia arvensis. I first found the small and vulnerable colony of this bee in 1992 and it
was still present in 1994 but I could only find two females during a visit in 1995, when
the quantity of scabious was much reduced by the drought conditions. The bee was
recorded in the Colchester area by Harwood at the end of the last century and it is just
possible that it may survive elsewhere if there are sites where scabious still occurs in any
quantity.
Some parts of the Glemsford site seem to represent old unimproved remnants and this is
exemplified by the presence of Meadow Saxifrage Saxifraga granulata by the edges of
the lichen heath and old railway track and areas of sedge marsh by the side of the River
Stour. Like other sites which have in recent years proved to be of particular importance
for invertebrates, Glemsford Pits possess a complex mixture of old habitats combined
with more recent disturbed habitats. The sand and gravel pits were probably first
excavated during the war, but sandy banks and sparsely vegetated ground still remain.
This mixture of unimproved and disturbed habitats is found in important sites of the East
Thames Corridor for example at Mill Wood Pit, Broom Hill and Mucking Heath (Orsett
Golf Course) in Thurrock and Eastbrookend (Dagenham Chase).
Peter Harvey