172
THE ESSEX NATURALIST
enormous variation in mandible size in the former sex. Figure 4
shows the heads of two extreme examples. Imms (1957) points
out that in the Lucanidae there are often three forms of the male
with short, medium and long mandibles. There is some indica-
tion from the figure that this is the case here, peaks occurring at
34 mm., 42 mm. and 52 mm. Another noticeable feature is the
change in the shape of the head associated with size, it being quite
smooth in the small males and very strongly ridged in the large
ones. The form of the mandibles is also found to be variable. It
should be pointed out that no correlation was found between size
and locality.
References
Donisthorpe, H. (1941). The Distribution of Lucanus cervus L. (Col.,
Lucanidae) in Britain. Ent. mon. Mag., 77: 198.
Fletcher, T. B. (1941). Lucanus cervus L. (Col., Lucanidae) in Gloucester-
shire. Ent. mon. Mag., 77: 252.
Hall, D. G. (1961). The Stag Beetle Survey—First Report. London Nat.,
40: 80.
Imms, A. D. (1957). A General Textbook of Entomology. Methuen.
The Beetle Lathridius bifasciatus Reitter in Essex
By P. M. Hammond
This small Australian beetle was introduced to the British
list on specimens taken at Esher Common and Chipstead, Surrey,
in October 1950 by A. A. Allen (1951). An earlier capture, by
E. Lewis at Godstone, Surrey, in July 1949, has been recorded
by Side (1956). Since 1951 this species has been found in most
south-eastern counties, but not elsewhere in Britain. There are
now records from Surrey, Kent, London, Middlesex, Essex,
Hertfordshire, East and West Sussex, Berkshire, Oxfordshire,
East Suffolk, Cambridgeshire, and Huntingdonshire. As there are
numbers of assiduous and reliable coleopterists in southern Eng-
land, and as L. bifasciatus is easily recognisable, the temporal
sequence of recorded captures of this species probably reflects
fairly well its actual spread. A gradual increase of range from a
centre somewhere south of London seems to be indicated. The
first records for Oxfordshire, Cambridgeshire, and Huntingdon-
shire, the counties furthest from this centre, are after 1960.
This paper is concerned with the occurrence of L. bifasciatus
in Essex. The first record for this county is by Side (1956), from
Stanford-le-Hope in November 1954, and this remains the only
published record for Essex. Since 1957 I have collected in most
parts of Essex with an eye kept open for L. bifasciatus, and have
been fortunate to receive a number of lists of beetles from various
localities in the county from other coleopterists. Evidence regard-