94
THE ESSEX NATURALIST.
side of the abdomen and nest in crevices in walls, dead trees, posts;
also in locks, snail shells and other suitable cavities, or in the
ground ; in clayey districts dead wood is more favoured. Sand
and earth are mixed with a secretion to form the cells. They are
known as Carpenter and Mason bees. The commonest and most
widely distributed is rufa, L. ; Billericay, Hale End, etc ; is.
parasitised by Chrysis ignita ; common on flowers of Brassica.
Pilicornis, Sm. Colchester district ; rare. Caerulescens, L.
Generally distributed ; Billericay, Hale End, etc. ; usually nests
in posts and walls, but it burrows in a hard path in my garden.
Ventralis, Panz., Billericay, Colchester district, etc. ; of similar
habits to the preceding, on hawkweeds and thistles. Bicolor,
Schk., nests in snail shells and banks ; very local ; Aldham,
Lexden, Purfleet. Spinulosa, K., nests in snail shells and
frequents the flowers of scabious, yellow composites, thistles and
knapweeds ; Colchester district ; local.
Chelostoma, Latr., nests in crevices or makes burrows in posts
and rails, also in straw and reeds ; the males sleep in flowers or
extend themselves horizontally from grass, tendrils, etc., which
they grasp with their jaws. They are parasitised by Chrysis-
ignita and cyanea and Faenus assectator and several species of
Ichneumon-fly. Florisomne, L., generally distributed ; Billericay,
Hale End, etc. Campanularum, K., frequents the flowers of
Campanula rotundifolia, and is found only where that plant grows
freely ; Colchester district.
Sub-Order VESPOIDEA.
We now pass on to the "Solitary Wasps," all the British
species of which belong to a single family, Eumenidae, sometims
known as Keyhole-wasps because some of the species have been
found nesting in keyholes ; more often they are called Mud-
wasps because they use mud or soft clay for their cells ; these
are fashioned in tubular burrows in banks or in hollow stems,
holes in walls and similar cavities, and the cells are provisioned
with the larvae of lepidoptera or coleoptera. The wasps frequent
flowers, and they sting severely, but this does not protect them,
from parasitisation by Chrysis ignita.
Hoplopterus spinipes, L., nests in sandy banks usually, but
sometimes in stiff clay, its burrows being easily recognisable 
by the tubular spout-like entrance, projecting and curved down.