18 TRANSACTIONS OF THE 
The mud-wasp Osmia is not at all averse to rented 
apartments and places her dainty brownish cells in the 
empty cell of the common eastern mud wasp. The cells 
are so arranged and shaped that they will exactly fill 
the cavity of the mud cell. 
The cells are extremely dainty, being composed of 
chewed plant fibres and plant hairs of a reddish brown 
color. They are very firm in texture and will resist 
considerable pressure before bending. In leaving the cell 
the young bee may emerge either through the concave 
end of the cell or through the side of the cell. The adult 
closely resembles the Snail-shell Osmia. 
The Pine Osmia is a pretty little greenish bee which 
builds its nest under the overlapping scales of the pitch 
pine. She does not waste extra labor in constructing 
a burrow for herself but finds the abandoned tunnel of 
a grub or wasp and places her tiny cocoons therein. 
These are placed end to end and are separated by thick 
partitions of chewed vegetable matter. The material used 
in the nests under observation was charcoal. The plug 
closing the burrow is likewise of charcoal and about 
half an inch long. 
The burrows of the mud wasp which builds in 
similar situations are always supplied with mud partitions 
and their burrows are always closed with a plug of mud. 
The character of the partitions may be relied upon for 
determining the ownership of the nests. 
The Snail-shell Osmia is, however, the aristocratic 
member of the family and while she has long been known 
in Europe has never before been described from America. 
They choose for themselves dainty houses of pearl, the 
deserted shell of Helix. The adults emerge early in the 
spring from the middle of April to the first of May in 
the vicinity of Ithaca, N. Y., the only locality from which 
they have been reported. 
The adults spend the first two or three weeks in the 
shells and on cool days may be found there often four or 
five in one shell. The males are much smaller and usually 
occupy the inner spirals, often crawling into the third 
