The insects known as caddisflies and mayflies are abundant in Arizona. These two insects dwell and breed near natural water bodies, and it is not uncommon for mayflies and caddisflies to swarm large populated areas located near lakes and rivers. For example, back in 2015, massive swarms of caddisflies terrorized residents of Bullhead City. This Arizona city is located near the Colorado River, so residents were used to occasional caddisfly swarms. However, the summer of 2015 saw repeat swarms that were so unpleasant that real estate prices in the city dropped drastically, as nobody wanted to retire to the city knowing about the swarms. Mayfly swarms can also be a nuisance for Arizona residents, as one resident of Oak Creek reported a mayfly swarm as large as 30 by 30 meters. At the moment, residents located near Lake Erie in Ohio are being bombarded with repeat mayfly swarms that are literally covering houses. These swarms are large enough to be picked up on weather radar. While it is well known that both caddisflies and mayflies can be a nuisance, their negative effect on human health is not so well known. Much like cockroaches and dust mites, mayflies and caddisflies are two arthropods that can induce allergic reactions in sensitive individuals. In some cases, these insects can induce asthma attacks, hives, skin irritation and eczema.
Given the caddisflies appearance, it should not be surprising to learn that they are closely related to moths and butterflies. Much like moths and butterflies, caddisfly wings are covered in easily detachable scales that serve as airborne allergens. These scales are a source of both indoor and outdoor allergens, and inhaling these scales can induce asthma attacks. Mayflies, on the other hand, do not spread airborne allergens; instead, the discarded skins shed by mayflies serve as environmental allergens. Although their discarded skins are not as readily airborne as the dust-like scales on caddisfly wings, these discarded skins can be blown about in the wind, making it easy for people to inhale this allergen. Mayfly allergens have been shown to induce seasonal asthma symptoms and eczema. Once case report describes in individual who developed “huge” hives as a result of making contact with mayfly allergens. Keeping these insects out of homes is particularly important to prevent the development of allergies or the worsening of existing allergies.
Have you ever witnessed a caddisfly or mayfly swarm?