PRESERVED INSECT FAUNA OF GLACIERS OF FREMONT COUNTY IN WYOMING - INSIGHTS INTO THE ECOLOGY OF THE EXTINCT ROCKY-MOUNTAIN LOCUST

From 1989 through 1992, preserved insect fauna of Knife Point, Bull Lake, and Upper Fremont glaciers (Wind River Range, Fremont County, Wyoming) was examined. Knife Point Glacier contained the first intact, glacially preserved grasshopper specimens found in the past 40 yr. These specimens were found below a crevassed region, and available evidence indicates that they may have been concentrated and preserved within a crevasse 140 +/- 50 yr ago. Morphological assessments of these bodies and cluster analyses of mandible and tibia measurements established that all but one or two of the exposed deposits were comprised of the extinct Rocky Mountain locust, Melanoplus spretus Walsh. Examination of distinct summer-melt strata indicates that this species was deposited at random intervals over a period of 300 yr. The floating section of strata also contained the first known glacial remains of swarms of the extant migratory grasshopper, Melanoplus sanguinipes (F.), and the first record of an insect other than grasshoppers (a parasitic wasp, Copidosoma sp.) having been periodically deposited. A total of six insect orders was found on this glacier. Aerial and runoff samples indicated that the rate of accidental insect deposition on the glacier is very low, and the rate of loss of material from the surficial runoff may exceed a million specimens per year. Bull Lake Glacier also contains at least one very rich deposit of well-preserved M. spretus, but other grasshopper remains appear to be widely scattered across the surface. Grasshopper remains from ice cores of Upper Fremont Glacier were dated from as early as 840 +/- 85 yr before the present, making this the oldest known glacially preserved insect deposit.