70 BULLETIN 94. 
those which are modified representatives of eastern species, and 
have probably reached Colorado in comparatively recent times, 
and those which are identical with species found east of the plains. 
Examples are as follows: 
(1.) Rocky Mountain Fauna.—TV. rubrella , schwarzi , mar ti¬ 
lt ell a, sc it a, grandis , civilis , etc. 
(2.) Modified eastern types.—TV. lepida , dacotana , vegana , 
zebrata , luteopicta. 
(3.) Typical eastern species.—TV. bella , albofasciata , cuneata 
superb a , • vincta. 
A few appear to be modifications of northwestern types; such 
are taraxacella , pecosensis , and possibly a few others. How far 
the species extend westward through Utah, etc., cannot be stated, 
owing to our almost complete ignorance of the Nomadce of that 
region; but the CaliforniaTVfl;«#ato-fauna is very distinct from that 
of Colorado, and the comparatively few species seen from Nevada 
indicate the extension of the Californian fauna,at least in part, into 
that state. The same indications exist for Idaho. 
The Nomadce of the mountains of northern New Mexico 
naturally resemble those of Colorado to a considerable extent, but 
our present lists show a rather surprising amount of difference, 
perhaps mainly the result of inadequate collecting. The species 
of southern New Mexico are different, and belong to a southwest¬ 
ern fauna which no doubt extends into Arizona and northern 
Mexico, though no knowledge of the Nomadce of those regions ex¬ 
ists, excepting a single record from Juarez in Chihuahua. 
It is hoped that the present paper will facilitate the study of 
Nomada in Colorado. The genus offers a very excellent field for 
research, and I venture to hope that some advanced student of the 
Agricultural College will interest himself in it. Undoubtedly 
more new species await discovery, while the habits of none of the 
species have been investigated. Very many species are known 
only in one sex, and there are probably some cases in which the 
opposite sexes of the same species have been described as distinct. 
As is well known, Notnada is parasitic in the nests of other 
bees, principally Andrena and Halictus. This parasitism should 
be carefully studied, and it is necessary to breed the bees from the 
nests in order to fully establish it. It is difficult for me to believe 
that the same species of Nomada can be parasitic in nests of both 
Andrena and Eucera , as has been reported of TV. alternata and TV. 
agrestis ; or in nests of both Halidas and Colletes as is recorded 
of TV. fare a. 
TABLE FOR THE DETERMINATION OF THE SPECIES. 
Vertex and mesothorax smooth and shining; male entirely 
black, females with a red abdomen (Montana).grimJsJfS Ckll. 
Not so, never entirely black. 1. 
