THE INSECTS OF ANCIENT AMERICA. 629 
few specimens while passing rapidly through the country, 
but he describes the shales in which they occur as a 
thousand feet thick, varying in color from a light cream 
to inky blackness, and crowded with the remains of in- 
sects and leaves of deciduous trees. Between sixty and 
seventy species of insects were brought home, represent- 
ing nearly all the different orders; about two-thirds of 
the species were flies, —some of them the perfect insect, 
others the maggot-like larve,—but, in no instance, did 
both imago and larva of the same insect occur. The 
greater part of the beetles were quite small; there were 
three or four kinds of Homoptera (allied to the tree-hop- 
pers), ants of two different genera,and a poorly preserved 
moth. Perhaps a minute Thrips, belonging to a group 
which has never been found fossil in any part of the 
world, is of the greatest interest. At the present day, 
these tiny and almost microscopic insects live among the 
petals of flowers, and one species is supposed by some 
entomologists to be injurious to the wheat; others believe 
that they congregate in the wheat, as well as in the 
flowers, in the hope of finding food in the still smaller 
and more helpless insects which congregate there. It is 
astonishing that an insect so delicate and insignificant in 
size can be so perfectly preserved on these stones ; in the 
best specimens the body is crushed and displaced, yet the 
wings remain uninjured, and every hair of their broad, 
but microscopic fringe, can be counted. 
The specimens came from two localities about sixty 
miles apart, called by Professor Denton Chagrin Valley 
and Fossil Cañon ; these two faunas are apparently quite 
distinct: the ants, the moth, the thrips, nearly all the 
small beetles and the greater part of the flies come from 
Fossil Cañon, while the larve are restricted to Chagrin 
Valley. 
