To date, 122 fossil insect assemblages
have been analysed from 13 sites, ranging from northern
Montana to southern Colorado (Fig. 1). These sites have yielded
about 300 insect taxa, predominantly beetles (Coleoptera). The
sites range in age from about 125,000 years to recent (Table 1). The
fossil beetle faunas include 200 taxa identified to the species level,
based on the external morphology of their exoskeletons. This is
roughly triple the level of diversity of identified species of mammals
from Late Pleistocene assemblages in this region, based on
data from Faunmap (Graham and Lundelius, 2010).