68
THE ESSEX NATURALIST
1961. The three recent specimens have been collected from
marshy situations.
Bombus pomorum (Panzer 1801-2). No Essex records. This
is our rarest bumble-bee, having been observed in Great Britain
on very few occasions.
Bombus pratorum (Linnaeus 1761). This is another fairly
common species in Essex, and recent records include Hawk Wood,
Chingford, 1.7.1958, A. C. Wheeler; Skipper's Island, Thorpe-le-
Soken, 15.4.1961; Billericay, 30.4.1961; and Little Easton, 14.5.
1961.
Bombus ruderarius (Mueller, O. F., 1776). The only record is
Colchester, 1894, from specimens in the Harwood and Cole-Pitch
collections.
Bombus ruderatus (Fabricius 1775). Colchester, no date, W.
H. Harwood; St. Osyth, 1893, Harwood (1884). No recent Essex
records.
Bombus smithianus (White, A., 1851). No Essex records. This
species is similar to B. muscorum and in this country is only found
in the north of Scotland, and the Scilly Isles.
Bombus soreensis (Fabricius 1777). No Essex records. It has
been taken in Suffolk, Morley (1935-1937), and at Royston Heath,
Hertfordshire, in 1924, Palmer (1925).
Bombus subterraneus (Linnaeus 1758). St. Osyth, 2.8.1884,
White; Colchester district, Harwood (1884). The only recent
record is Norsey Wood, Billericay, 30.7.1960.
Bombus sylvarum (Linnaeus 1761). Colchester, 1900, W. H.
Harwood. The only recent record is Navestock Park, 20.8.1960.
Bombus terrestris (Linnaeus 1758). This is one of our com-
monest bumble-bees and occurs over most, if not all, of the county.
PSITHYRUS Lepeletier 1833
These are the "cuckoo" bumble-bees and are parasites of
various Bombus species. The worker caste is missing; only males
and females occurring.
Psithyrus barbutellus (Kirby, W., 1802). Parasitic on B.
hortorum. Colchester, 1913 and 1914, W. H. Harwood. The only
recent record is Littlebury, near Saffron Walden, 28.6.1961.
Psithyrus bohemicus (Seidl 1837). Parasitic on B. lucorum.
No Essex records. Palmer (1925) records it from Stevenage, Hert-
fordshire.
Psithyrus sylvestris Lepeletier 1833. Parasitic on B. pratorum.
This is our commonest "cuckoo" bumble-bee. Records include
Colchester, 1896, W. H. Harwood; Epping Forest (near Wake
Arms), 25.8.1952; Scrub Hill, near Warley, 30.8.1959; Norsey
Wood, Billericay, 30.7.1960; and Walton-on-the-Naze, 3.9.1960.
Psithyrus rupestris (Fabricius 1793). Parasitic on B. lapidarius.
This is less common than the preceding species. Colchester, 1890
and 1893, W. H. Harwood; Hawk Wood, Chingford, 1.7.1958, A.
C. Wheeler; and Norsey Wood, Billericay, 30.7.1960.
Psithyrus sylvestris Lepeletier 1833. Parasitic on B. pratorum,