Over the course of our conversation, though, his tone took a turn. The caddisflies, Brady explained, were just the latest insect plague facing the city. Before the caddis, Bullhead saw a black fly infestation in the 1980s, the first sign that the ecosystem was out of whack. “I honestly believed when I moved here that our town would never grow because the black fly situation was so out of control,” he said. Like caddisflies, black flies are a native species, bloodsuckers whose aquatic larvae also grow up in the river. Brady remembers residents walking their dogs with insect head nets and helplessly waving their arms in front of their face. “The Bullhead salute,” they called it.

Black flies were finally controlled by introducing a strain of bacteria called Bacillus thuringiensis israelensis — Bti, for short — into the river. Bti produces a toxin that kills black fly larvae without making the water undrinkable or harming other creatures. “That has probably been one of the greatest things for Bullhead City’s growth,” Brady says. The city has expanded from a population of 10,700 in 1980 to over 40,000 today. But the Bti toxin is useless against the caddisfly infestation, which threatens to put a damper on the city’s future growth. “It’s a problem, and it could grow worse,” he said.

Although caddisflies don’t bite like black flies, their hairs and scales can send people into coughing and wheezing fits. Some unlucky souls have full-blown allergic responses, developing asthma, hives, and eczema. Befitting a creature that only expects to live a fortnight, their bodies are so mushy that if you try to brush them away, they’ll just smear across your skin and clothing. One angry resident told the town entomologist he had to wrap his kid up in plastic just to walk from the house to the car.

At night, the bugs are attracted to lights, and the riverfront casinos across the river in Laughlin draw them in from miles away. During the day, they hide out in the shade offered by waterfront vegetation and the alleyways between homes. Insecticides sprayed in the air don’t work well at controlling an insect that spends most of its life in the water, and you can’t just dump a poison in a river that’s headed straight for Phoenix. Some residents resort to household chemicals to kill them. “We spray a lot of Windex,” admits Brea Chiodini, who runs a dinner cruise on the Colorado called the Celebration. Others have taken out their frustration by incinerating masses of flies around their homes using handheld blowtorches.

Before the caddisflies came to Bullhead, they started pestering a small unincorporated community below Parker Dam, 88 miles downstream. Biologists caught 3.5 million caddisflies — about 12 pounds worth — there on a single summer night in 1999. Another 15 years would pass before they began laying siege to the more populous city to the north.