A Final Meal for the Ages

For World Mosquito Day, meet the “one in a million” fossil that proved fossilized blood is more than just science fiction

The mosquito fossils from northwestern Montana, like the recently described species Culisteta kishenehn shown here, reveal that mosquitoes have changed remarkably little over the past 46 million years. Dale Greenwalt

The National Museum of Natural History is iconic for stunning prehistoric showpieces like the Nation’s T. rex, the colossal Diplodocus skeleton or the gaping maw of Megalodon. But one of the museum’s most remarkable fossilized treasures is only a couple centimeters long. Just looking at it may give you the urge to scratch your skin or snag a fly swatter.

The fossil in question is a petrified mosquito imprinted on a shale slab and displayed under a magnifying glass in the museum’s Objects of Wonder exhibition. Compared with its exhibit-mates, which include treasures from the museum’s sprawling collection like Martha, the last passenger pigeon, hunks of mammoth blubber and original, hand-colored illustrations from John James Audubon’s legendary Birds of America, the mosquito appears quietly mundane.

One of the museum’s most remarkable fossils — a 46 million year old mosquito with a dark smear of fossilized blood preserved in its abdomen. Smithsonian Institution

However, a closer examination of its guts reveals something remarkable. Stained inside its abdomen, which looks like it’s been filled in with a sharpie, are the remnants of the blood the mosquito lapped up 46 million years ago. When it was described by Smithsonian scientists in 2013, it was the first known mosquito fossil preserved with a belly full of blood. For World Mosquito Day on August 20th, we thought it was time to spotlight this groundbreaking fossil.

This discovery seems right out of Jurassic Park, where scientists harvest “Dino DNA” from blood-engorged mosquitoes entombed in hunks of amber. For decades, the idea of blood fossilizing at all seemed to belong strictly to the realm of science fiction. Which is why Dale Greenwalt, a research associate in the museum’s Paleobiology Department, knew he may have stumbled across something special when he first placed the mosquito fossil under the microscope. “I immediately saw the enlarged and darkened abdomen and asked myself ‘Can this be a blood-engorged mosquito?’” 

The mosquito fossil hails from a stretch of the Flathead River in Montana’s Glacier National Park. While the region is now renowned for its fly fishing, Greenwalt has been venturing out there for fifteen years, angling instead for a rich assortment of ancient flies.

The banks of northwestern Montana’s Flathead River are covered in slabs of shale that preserve a rich assortment of fossil insects like wasps, beetles, water bugs and a multitude of mosquitoes. Dale Greenwalt

Though this area is now a rugged expanse of grasslands and snow-capped mountains, it was a muggy mosaic of subtropical forests and wetlands mirroring Florida’s Everglades during the Eocene Epoch 46 million years ago. With plenty of water and heat, this region was a mosquitoes paradise. Greenwalt has discovered several new mosquito species in the paper-thin shale of the Eocene Kishenehn Formation that flanks the river. Many of these ancient blood-suckers look nearly identical to the mosquitoes buzzing around today.

While the site is iconic for its preservation of tiny insects — intricate traits like wing veins, antennae and even color are etched in the rock — fossilized blood this old would be a first. So Greenwalt took the mosquito with the dark abdomen to Tim Rose, the manager of the museum’s analytic laboratories who helps scientists examine everything from ancient artifacts to hunks of asteroids with heavy duty electron scanning microscopes. 

With the delicate fossil under the scanning microscope, Rose recorded how X-rays deflected off of different parts of the fossil to decipher the molecular makeup. He was looking specifically for which parts of the mosquito contained iron, a key component of red blood cells. “If we have remnant blood, there should be higher iron content in the abdomen than any other part of the mosquito,” Rose said.

The  X-rays confirmed a spike of iron molecules in the mosquito’s darkened belly. Further testing of the abdomen revealed the remnants of hemoglobin, the molecules that give blood its characteristic crimson color. “Insects do not make hemoglobin–it had to come from the mosquito's host,” Greenwalt said. They had drawn fossilized blood.

Smithsonian paleontologist Dale Greenwalt holds up the slab of shale containing the first blood-engorged fossilized mosquito ever described. James DiLoreto
The news of their discovery made headlines around the world. “The Jurassic Park connection ensured that it got a great deal of publicity,” Greenwalt recalled. However, for anyone hoping to re-engineer dinosaurs like T. rex with this mosquito may be a little disappointed. First off, the blood is 20 million years too young to be from any of the non-avian dinosaurs that terrorized parkgoers on the big screen. There’s also no way of telling what animal’s blood the mosquito drank before it died. Lastly, 46 million years has taken its toll on the quality of the sample, according to Rose. “Only a fragment of blood was found,” Rose said. “There’s no DNA, so you can’t get too excited about that possibility.”
The world’s oldest known blood-engorged mosquito specimen sports an outsized scientific importance despite its tiny size. Jack Tamisiea

Greenwalt contends that this makes the fossil no less remarkable. “This preservation is a ‘one-in-a-million’ occurence and is due to the unique preservational environment in the ancient lake,” said Greenwald. All the blood sloshing inside of its abdomen would have caused it to inflate like a balloon, making the mosquito incredibly fragile. Even the slightest pressure could cause this blood balloon to burst. Yet the insect tumbled into the water where it was encased in a sticky algal bloom, sank to the bottom of the pond without being snapped up by a hungry fish and was buried with its swollen stomach intact. 

Over the years, Greenwalt has collected around 8,000 insect specimens from northwest Montana, including a few more well-fed mosquitoes. “We continue to find new blood-engorged mosquito specimens, many of which are much better preserved than the original,” Greenwalt said. They remain  “the only fossil blood-engorged mosquitoes known to science.”

Related Stories:
The Secret Lives of Mosquitoes, the World’s Most Hated Insects
Get to Know the Scientist in Charge of Smithsonian’s 1.9 Million Mosquitoes
How Museum Collections Advance Knowledge of Human Health
Meet the Scientist Who Knows the Buzz About the Asian Giant Hornet