Falcon – Prince Henri, an 8-year-old with a regal demeanor and a stoic personality, was about to lose his mind.
He had been spotted by the keen eyes of a bloodthirsty monster that cruised the sky above a field in this small town east of Colorado Springs. The winged dragon swooped low and then attacked, biting the prince directly on his exposed rump.
The pain sent him into a rage. He kicked violently and rammed his head into the side of his metal trailer.
The prince – and maybe we should have pointed this out earlier – is a horse.
His attacker, all quarter-inch of him, was a stable fly, Stomoxys calcitrans, a devil of an insect with a sword-like proboscis, that – along with millions of relatives, including horse flies, deer flies, black flies, biting gnats and horn flies – has swarmed across the plains of eastern Colorado this summer.
The masses of tiny insects have put farmers and ranchers in their barns for days at a time, spraying bug repellant and cleaning the stalls and then spraying some more. Hikers and anglers and others who trek through the mountains have felt the wrath of the bugs, too, often in the forests where typically the things that bite have fur, not wings.
But the cattle and horses of the plains have suffered the most during this summer, one of the worst for biting insects that most people can remember.
The cause, according to those who know, is moisture. And manure.
“Just another highlight from our blizzards,” said Susan Russell, who, along with husband Curtis, owns WW Feed and Supply in La Junta. The region was pounded by nightmarish snows some eight months ago.
And then the snows melted. Water trickled and roared and gathered. Horse and cow manure stayed wet – the perfect breeding environment for the nasty flies. And unimaginable dark clouds of them, two and even three generations of flies, emerged and began a summer-long search for blood.
Swordlike mouths, savvy brains
Alexandre Latchininsky, a Russian-born assistant professor of entomology at the University of Wyoming, knows a thing or two about biting flies.
“Although I should point out,” he said in a heavy accent, “that my primary specialty is grasshoppers.”
Nevertheless.
“Stable flies, first of all, they look very much like housefly,” said Latchininsky. “People blame housefly for biting them, but houseflies do not bite. Stable flies, they have piercing, sucking mouth parts and feed on blood many times each day.”
And inside the tiny heads is a brain.
“Surprising part,” Latchininsky said, “is that stable fly knows where to land on horse or cow to stay safe. They land on feet or stomach of the animal so the tail cannot swat them.”
Unlike mosquitoes, both the male and female stable flies feed on blood. The female drinks it for reproduction purposes: she needs the protein-rich blood to produce viable eggs. The male, well, he just likes it.
Together they swarm and bite and suck and make life downright miserable for livestock, dogs and people such as Rexann Frank, who owns the great black horse attacked in the Falcon field, a horse with the formal name of Magnat Prince Henri.
“He just absolutely hates the biting flies,” Frank said. “Sometimes they’ve been so bad this year that his body was covered with welts the size of my fist.”
Frank, with a master’s degree from Colorado State University in entomology, and her veterinarian husband have fought back, spraying Prince Henri and their other horses with botanical solutions such as marigold extract – they don’t use chemicals – that ward off the fly attacks. But the sprays are only effective for half a day, she said. So they spray almost continuously.
And, as they’ve done for five years, they also unleashed a swarm of fly predators in the spring, savage little wasps – purchased via catalogs – that feed only upon fly larvae.
“This year, even that didn’t help,” she said.
A bounty of breeding places
These days Prince Henri spends most of his time draped in a gray, full-body bug suit and face mask. The light nylon mesh lets in the cooling air but keeps the nasty flies off.
In typical years, a good sanitation program keeps the biting fly problem down to little more than a nuisance. Experts tell ranchers and farmers to get rid of piles of manure, wet straw and grass clippings and to manage their compost piles. This year, all of those standard measures have failed.
Like the more urban areas of Colorado, the plains received heavy snows in December and early January. But then came more blizzards in the late winter and early spring. Then heavy rain.
“Stable flies develop in straw mixed with old manure, and horn flies develop in fresh manure,” said Frank Peairs, an entomologist at CSU in Fort Collins. “It usually dries quickly and the larvae die. But this year that didn’t happen.
“And the black flies, they develop in clear, running water. This year the pastures are full of those little creeks.”
So severe is the problem that even Colorado’s mountains – typically immune from the fly plagues of the plains – are getting a dose of trouble, according to Rocky Mountain National Park biologist Jeff Connor.
“Black flies surprised me the other day. And the biting gnats, the ‘no-see-ums,’ they’re here too. In my 20 years in the park, this has been more of a problem than in any other summer.”
But where the snows of winter were the greatest, so now are the problems. Around La Junta, some 150 miles southeast of Denver and 65 miles east of Pueblo, it has been downright nasty.
“The biting flies have been so thick, so persistent, that it has affected weight gains in cattle,” said Susan Russell. “The cattle are too busy fighting the flies to graze. The snows came and they had to fight that fight, and now we’re asking them to fight another fight.
“I’ve seen white cows this summer that looked black just from the blanket of flies on them.”
Toughing it out until the frost
The cattle don’t fight alone. Ranchers have many weapons, including a food additive that works from the inside out, getting absorbed into the blood to repel the attackers. And there are cattle rubs, five or 10-foot-long fabric strips treated with insecticide and stretched between trees or fence posts on trails where the cattle walk.
Some cows inadvertently rub along the strips and get the bug repellent on them. Others, well, they’re smarter. “Many of them figure out that the insecticide keeps the flies off,” Russell said. “So they seek out the rubs and rub their backs and heads against it on purpose.”
Other livestock have a more natural approach. Cows and horses often stay together in large groups, forming a collective tail-swooshing society to keep the flies from settling. Scientists say the biting will end about mid-October, when nighttime temperatures kill off the adults and larvae.
It will be a summer long remembered by those who neigh and moo and the people who love them.
“It’s horrible, just horrible,” said Debbie King of Parker, who has battled since May against the stable flies, horn flies and especially the tiny black flies, also called buffalo gnats, that have been attacking her show horse, Goetz Grace.
“She is very sensitive,” King said of her mare. “She’s a princess. She doesn’t deal well at all with biting flies. She stomps her feet and shakes her head, and the flies just drive her crazy.”
Staff writer Rich Tosches can be reached at rtosches@denverpost.com.
This article has been corrected in this online archive. Originally, due to an editing error, a photo caption referenced an incorrect location for Rexann Frank’s barn. The photos were taken in Wellington.
