3. ANDRENA NIGROAENEA Kirby. A male enlarged approximately three 
times natural size. 
Drawn from a specimen preserved in the Museum of Comparative Zool- 
ogy, Harvard University. 
4, ANDRENA TRIMMERANA Kirby. A male enlarged approximately three 
times natural size. 
Drawn from a specimen preserved in the Museum af Comparative Zool- 
ogy, Harvard University. 
5, Opurys rusca Link, A single flower enlarged approximately three 
times natural size. The labellum varies considerably in color, but. is 
usually dark purple, sometimes with a narrow golden yellow border. 
The markings that are supposed to simulate the wings of a female An- 
drena (probably the partly folded wings) , are lighter in color than the 
rest of the labellum and are more or less iridescent with greys and 
blues. The wing-like pattern formed by the iridescent area is in reality 
densely beset with minute glandular hairs, but these are so minute that 
to the unaided eye the surface from which they emerge appears to 
be quite smooth, The rest of the labellum is velvety or even hairy 
almost to the margin and under the microscope is sharply demarked, 
by the difference in the length of the hairs, from the area occupied 
by the iridescent wing-pattern. Insome forms of this species the hairs 
are much elongated, as in O.speculum, just within the margin of the 
large middle-lobe. At the base of the labellum beneath the rostellum, 
there is a shallow cup-like depression with a broad opening. The ante- 
rior margin and wall of this depression are densely covered with short 
glandular hairs and the opening is sufficiently large to admit the pos- 
terior part of the abdomen of an insect that effects pollination, while 
the rostellum is sufficiently close to the opening to touch the posterior 
segments of the insect’s body and to affix the pollinia in preparation 
for transportation to another flower. 
Between O. fusca and O, lutea the differences are chiefly those to 
be found in the color of the labellum, the fundamental structures of 
the two species being very similar. 
[ 24 ] 
