Specific Characters in the Bee Genus Colletes 5 
tion. Following the nomenclature adopted by Rev. Morice, the 
general construction of the armature is as follows: There is a 
basal portion, the cardo, upon which articulate two pairs of for- 
ceps-like structures, the stipites and sagittae. Each stipes or 
outer pair generally appears three-jointed when viewed from the 
dorsal side, there being a small, pilose apex, a larger central joint, 
and a large basal joint which bulges in to meet its fellow below 
the sagittae; between the basal and central joint is usually a 
transverse suture, the notch. The sagittae or inner pair are two 
rods of chitin of very variable form, much dilated basally, and 
apically expanded into a membranous wing. Protruding from 
the inner base of each stipes and partially covered by the dilation 
of the sagitta in the dorsal aspect, is a bifid structure the inner 
surfaces or jaws of which are tuberculated, the volsella. These 
structures, as Rev. Morice points out, are all of more or less value 
in distinguishing the species, but are not nearly so convenient as 
the seventh ventral plate. The help of these concealed structures 
to the systematist can scarcely be overestimated. Not only do 
they furnish most excellent criteria for deciding upon the specific 
identity or distinctness of two forms in hand, but a species can 
usually be told at a glance, thus doing away with the necessity of 
toiling through tables of slight external characters—every spe- 
cies, one may almost say, bears its own label. In this paper illus- 
trations of the seventh ventral plate and outline drawings of the 
armatures of each of the eighteen species known to the writer 
are given; of the eight remaining species five are unknown in the 
male and the other three are known only by the types, which are 
not available for dissection. 
The pronounced sexual dissimilarity in this genus renders the 
proper matching of the sexes often a matter of unusual difficulty. 
The males are almost always smaller than the females (larger, 
however, in the aestivalis group), more slender, and more densely 
pubescent, usually with a dense clypeal beard. The antennae are 
usually much longer and the joints differently proportioned, the 
scape being short and cylindrical instead of long and clavate. 
The malar space is almost invariably longer, legs more slender, 
fasciae narrower, spurs not pectinate and coxal spines obsolete. 
47 
