Ancient Insect Discoveries From Across Colorado (Part 2)

In the second part of a two-part series, we look at Pleistocene beetles that feasted on mammoth dung, Eocene tsetse flies that are now confined to Africa, and a prehistoric wasp that went extinct 10 million years ago.

Dung Beetles (Snowmastodon Site)

Fossil from Snowmastodon excavation site at Snowmass Village, Colorado
Fossils from Snowmastodon site | Richard M. Wicker and Denver Museum of Nature & Science

When construction crews arrived at Snowmass Village near Aspen in 2010 to expand the nearby reservoir used for making snow, the last thing they expected to unearth was an entire Pleistocene ecosystem. Dating back 55,000 to 140,000 years ago, the Snowmastodon site yielded a plethora of ancient specimens, ranging from mammoths and mastodons, to lizards, plants, and insects galore.


Most abundant amongst the insect specimens were beetles, including 18 different species of dung beetles. Researchers were not surprised by this find. In an ecosystem where mammal megafauna like mammoths, mastodons, and ice-age bison thrived, dung beetles would be expected to live alongside them. Of the dung beetle species identified at the Snowmastodon site, one was notably specialized in feasting on mammoth dung.


While many of the fossilized insects and plants discovered at the Snowmastodon site still thrive in the modern day, they no longer exist in the Colorado Rocky Mountains. At some point in the last 140,000 years, their native distribution shifted to the Pacific Northwest. There they found warmer, wetter conditions like those prehistoric Colorado once provided.

Dung Beetles feasting on horse manure
Modern dung beetles feasting on horse manure | Duwwel

By the scheduled end of the dig in 2011, the excavation team had recovered over 35,000 bones of varying sizes, representing nearly 50 different species. The Snowmastodon site was considered the most productive high-elevation Pleistocene site ever discovered. Still, only 10 percent of the site had been excavated when the reservoir was refilled. While leaving so many potential bones and fossils buried in the ground seemed unfathomable, researchers said it wasn’t uncommon for digs to end before sites have been fully processed.


According to paleobotanist Ian Miller, “This is the perfect cold, low-oxygen environment for those fossils. And they’re quite safe from vandalism. Nobody’s going to disturb those fossils until we’re ready to go back for them.”

Tsetse Fly (Florissant Fossil Beds)

Tsetse Fly Fossil from Florissant Fossil Beds in Colorado
Tsetse Fly fossil from Florissant Fossil Beds | University of Colorado Museum of Natural History

Volcanic eruptions that occurred 34 million years ago created the fossil-rich Florissant Fossil Beds west of Colorado Springs. The ash from these eruptions trapped and preserved an entire Eocene ecosystem, including over 1,100 different insect species. Infamous among them was the destructive tsetse fly, a scourge of modern Africa.


Existing nowhere in the modern world outside of the African countries located between the Sahara and Kalahari deserts, bloodthirsty tsetse flies wreak havoc on agriculture and human health. A deadly parasitic illness called African sleeping sickness is spread by these pests. Humans, livestock, and wild animals can all be fatally sickened.

A tsetse fly on a branch
Modern tsetse fly | International Atomic Energy Agency

While the rest of the world is fortunate to be spared the destruction of tsetse flies, this wasn’t the case in prehistoric times. As researchers discovered when unearthing a 34-million-year-old tsetse fly fossil at the Florissant Fossil Beds, tsetse fly distribution was much wider during the Eocene epoch, extending all the way into present-day United States. Researchers believe this can be explained by the dramatic climate shifts that have occurred since the Eocene epoch.


Planet Earth was much warmer and wetter during the Eocene epoch, and had a higher level of greenhouse gases in the atmosphere. Colorado was a prehistoric topical forest back then. With a climate closer to that of the African tropics, it provided ideal conditions for tsetse flies to thrive.

Wasp (Florissant Fossil Beds)

Fossil Wasp Palaeovespa (Florissant Fossil Beds Colorado)
Wasp (Palaeovespa) fossil from Florissant Fossil Beds | National Park Service

Another significant insect fossil discovered at the Florissant Fossil Beds is an ancient wasp species belonging to the genus Palaeovespa. A remarkably intact specimen, the fossilized wasp provided researchers the ability to examine and understand the adaptations that allowed Palaeovespa to exist in its demanding prehistoric setting.


Researchers confirmed their belief that the Palaeovespa genus emerged around 44 million years ago, then went extinct 10 million years later. Despite its prehistoric extinction, this wasp was highly similar to modern predatory social wasps. It was a nasty predator and fierce defender of its nest, and possessed a venomous stinger.


According to the National Park Service, this species of wasp filled an important ecological niche in the Florissant Eocene ecosystem. It also serves today as the official mascot of the Florissant Fossil Beds National Monument.