When Craig Vallon and his spouse Denise relocated to Bullhead City, Arizona, in 1973, Craig felt fortunate to have found his dream home. The couple, who had met as teenagers in Los Angeles, were drawn to this small city by its affordable living, nearby casinos, and outdoor activities. As educators, they embraced the local culture, with Craig even dressing as the famed mountain man Jedediah Smith for educational talks. Post-retirement, he cherished watching the Colorado River flow by from his trophy-adorned home.

By spring 2015, Craig began noticing small, brown, moth-like insects congregating near their outdoor lights. Initially few in number, these pests quickly multiplied into a thick swarm hovering over the river, creating an unsettling sight. During the day, they clung to windows, leaving greasy smudges that obstructed the view. Denise found the swarms so overwhelming that hosting outdoor dinners became impossible, with insects contaminating the food.

Craig soon identified these invaders as caddisflies, a native species thriving in clean waters. While some areas of the Colorado River faced a decline in these insects, officials heralded their presence in Bullhead as a sign of a flourishing ecosystem. Craig, however, felt dismissed and decided to raise awareness about the burgeoning issue. He placed an advertisement on a digital billboard on Highway 95, warning potential property buyers of the infestation and suggesting a simple solution: increase trout populations in the river.

Despite Denise’s concerns about legal repercussions, Craig funded the billboard for a week, later receiving donations from neighbors to extend its run. His efforts soon drew the ire of city officials. In a quest for community awareness, he distributed flyers, only to face federal warnings from the post office.

The caddisfly population explosion was likely linked to the river, where they spend most of their lives. The Colorado River, stretching 1,450 miles from the Rockies to Mexico’s Sea of Cortez, underwent a transformation from a muddy waterway to a crystal-clear river due to numerous dams. This alteration disrupted its natural ecology, with wild, dynamic rivers becoming increasingly rare.

Craig Vallon passed away last year, but the caddisfly crisis remains unresolved, with local authorities employing entomologists and testing various pesticides and biological controls. Despite four years of attempts, their effectiveness has been limited.

In nearby Laughlin, Nevada, the once-popular riverwalk is now littered with negative reviews on TripAdvisor, warning potential visitors about the overwhelming bug presence. This situation reflects a broader ecological crisis, as a million species face extinction, largely unnoticed in everyday life. However, some insects, including caddisflies, are thriving in this post-extinction environment, exploiting a lack of predators and competition.

While many species are declining due to pollution and habitat loss, some, like the mountain pine beetle, have surged in population, devastating forests. Similarly, excessive nutrient runoff has led to explosive mayfly populations in Pennsylvania, necessitating street sweeps to manage their remains.

Biodiversity relies on a balance of species within an ecosystem, with occasional population booms being natural. However, when one species dominates, it indicates a significant ecological issue. Craig Vallon’s observations echo concerns from ecologists about native species transforming into pests.

The construction of dams has drastically altered landscapes, leading to simplified ecosystems that favor certain species over others. In places like the tropics, mosquito populations have surged due to damming, while in the Pacific Northwest, bird populations have thrived at the expense of endangered salmon.

The caddisfly situation in Bullhead City serves as a cautionary tale about the challenges facing rivers and dependent communities. As Albert Graves, an engineer, noted, effective solutions seem elusive.

Davis Dam, towering over the landscape, embodies the drastic changes brought about by human intervention. Originally built to harness the river’s power, it facilitated the growth of Bullhead City by attracting residents with its recreational opportunities.

The most common caddisfly species in the area, Smicridea fasciatella, thrives in the river’s depths, where larvae cling to rocks and feed on algae. These larvae can reach extraordinarily high densities, leading to a spectacular yet overwhelming emergence phase where adult caddisflies swarm above the water.

During a conversation with Bullhead’s mayor, Tom Brady, he expressed his love for the city but lamented the caddisfly invasion as yet another insect plague. Prior to the caddisflies, the area faced a black fly infestation, an early warning sign of ecological imbalance.

Control measures for black flies involved introducing a harmless bacterium that effectively reduced their population, fostering growth in Bullhead City. However, this method has proven ineffective against caddisflies, threatening the city’s future development and quality of life. While caddisflies do not bite, they can cause allergic reactions and discomfort.

As night falls, the bugs are irresistibly drawn to lights, with casinos attracting swarms from miles away. Residents often resort to unconventional methods, like using household cleaners or blowtorches, to manage the invasive insects.

The caddisfly invasion began downstream and gradually moved northward, overwhelming Bullhead City in 2015. Though they had existed previously, their recent numbers were unprecedented, leading to an extended season of infestation.

Residents now worry that property values will plummet, prompting an exodus from the riverfront. Despite being crucial to the ecosystem, caddisflies face their own extinction threats due to environmental degradation, with many species at risk.

Although some caddisfly populations are booming downstream from dams, the overall picture is grim for aquatic insect species globally. Studies highlight the troubling rise of caddisflies in various locations, particularly downstream from dams, suggesting a troubling ecological trend.

Joe Iburg, the former entomologist in Bullhead, noted that the transformation of the riverbed due to dam construction has created a perfect habitat for caddisflies. The reduction in sediment flow has resulted in clearer water, supporting algae growth and providing a steady food source for caddisfly larvae.

Other natural factors that once kept caddisfly populations in check have also diminished. Native dragonflies and fish that preyed on caddisflies have seen drastic declines, further tipping the balance in favor of these insects.

Many residents, including Craig Vallon, linked the caddisfly surge to the shutdown of a local fish hatchery, which had previously stocked the river with trout. However, Iburg found that the introduced trout were not adequately preying on caddisflies, as many were caught by anglers or consumed by larger fish.

Efforts to combat caddisflies in the past, such as a failed attempt in Montreal during the 1967 World’s Fair, highlight the challenges of managing insect populations. In Scottsdale, Arizona, a unique mechanical solution was employed, yet the insects simply reattached downstream.

Iburg’s advice for residents included using yellow bulbs to deter caddisflies and exploring the use of pheromone traps, though he acknowledged that significant control measures might require drastic actions like temporarily halting water releases from dams.

The ongoing alterations to our ecosystems demand active management to maintain balance. From controlled burns in forests to beach replenishment efforts, humans are forced to intervene continuously. In Bullhead, the future remains uncertain as residents face a new reality shaped by these ecological changes.

The U.S. Bureau of Reclamation is experimenting with river flow management to restore the Grand Canyon’s aquatic ecosystem, but the long-term effectiveness of these measures is yet to be determined.

Dam removal has been suggested as a way to restore river health, but the dependence on Colorado River dams complicates this solution. Bullhead City’s existence is intertwined with the dam, and its residents must adapt to this new ecological landscape while grappling with the challenges posed by the caddisfly invasion. Recently, a new entomologist was hired to tackle the issue, and as Denise Vallon reported, the caddisflies are back in droves, signaling a continued struggle ahead.