2 
BULLETIN OF WIPCOXSIX NATURAL LIISTORY SOCIETY. VOL. 5, NO. 1. 
whiteness of snow or of other transparent substances in a fine state 
of division. Iridescent effects and blues are due to obscure physical 
phenomena wliich are not entirely understood. Gra3^s are produced 
b}' combinations of the conditions which produce black and white. 
President Teller thanked Dr. Strong in behalf of the Society for his 
entertaining- address and for his kindness in coming to Milwaukee to 
lecture before the Society. 
The meeting then adjourned. 
Milwaukee, Nov. 8, 1906. 
Combined meeting* of the Biological sections. 
President Teller in the chair and 12 members present. 
As no topics for discussion had been announced and no program 
prepared, those present were loathe to start the proceedings. Finally, 
Dr. Graenicher called attention to two interesting cases of variation 
or mutation of instinct among bees. The first was Alcidainea producta, 
a species which hollows out steins, and the second a specimen belong- 
ing to a species of J/ e.^/r/f /nV^'. Both of these normally close the nest 
with a plug of malaxated leaf pulp, but in these two cases, out of a 
large number of nests observed, the female bees had used pieces of 
stone or gravel mixed in the pulp. He suggested that this was per- 
haps a. mutation in habits, but that it was more likelj^ an atavism, 
since the use of stones as building material was probably more primi- 
tive than the employment of leaves cut from plants. 
Mr. Brues said he agreed that this might be looked at as a muta- 
tion oi habit, but believed it was undoubtedly a reversion. He called 
attention to the bee genus Anthld'ium, certain species of which use 
plant material for their nests, while other very closely related ones 
utilize stone or gravel entirely, suggesting that the variation was per- 
haps not as profound as it would seem at first sight. Mr. Ward said 
that variations in nest-building among birds were common and often 
as striking as the cases among' bees mentioned by Dr. Graenicher. He 
cited the Caspian Tern, a species which he had seen utilizing shells to 
line its nests, a very unusual habit, since it usually uses no lining 
except a little plant matter. At the same time, he said, the species 
had departed from its usual solitary habits and was nesting in great 
numbers, and with a second regularly gregarious species, the Herring 
Gull. 
