76 
Psyche 
[June 
chile), Triepeolus (on Melissodes etc.), and others. They lay 
their egg alongside that of the host in the cell. Then, according 
to Fabre (’ 15), the parasite’s egg hatches out and its first instinct 
is to seek out and destroy the egg of the host. It then develops, 
usually throughout the winter to come out the next summer as 
the adult. Thus each bee and each genus has its own peculiar 
methods of nesting. Many more interesting details can be ob- 
tained from Fabre’s works. And many interesting facts remain 
yet to be found in nature. 
The small bees of the genus Perdita are found chiefly in 
the arid south-western region of the North American Continent. 
Some have been found in Canada (P. canadensis Crawfordfand 
Fig 3. — The pollen grains on the hind legs of the female are larger than the ocelli. (Hind 
leg of female X33 diameters). 
P. citrinella Grsenicher); others in Mexico (P. mexicanorum 
Ckll). 8 Between these two countries the bees of this genus are 
abundant, especially in New Mexico. P. albipennis, a western 
form, is found from South Dakota and Nebraska through 
Colorado and New Mexico into Texas, according to Grsenicher 
(’14). 
Before Professor Cockerell (’96) started his work on this 
genus, only 17 species were known. By 1896 he had added 53 new 
species to the list. Of these, 26 were known in both sexes, 26 
only in the male, 18 only in the female. The flower visiting 
habits of 50 species were known. Their nesting habits were as 
yet unknown. Fifteen years later, in 1911, he reported a list of 
8 Prosessor Timberlake informs me that the genus is recorded on the At- 
lantic coast from Guatemalo to New Brunswick; on the Pacific coast from 
Lower California to Victoria, British Columbia, at which latter place he has 
found an as yet undescribed species. He is at present describing some 
fifty new species, mostly from California. 
