Colorado, a state known for its diverse landscapes, also hosts an extensive variety of insects. From the sprawling eastern plains to the towering peaks of the Rocky Mountains, these varied environments provide habitats for numerous insect species.
Common Colorado Insects
Across Colorado’s varied terrain, many insect species are commonly observed. Butterflies and moths are frequent sights. Various types of beetles, such as the familiar ladybugs and dung beetles, also inhabit the state. Grasshoppers are abundant in grassy areas, while common bees, including honey bees and native bumblebees, play a significant role as pollinators, supporting plant life across different altitudes.
Insects of Health Concern
While many insects are harmless, some in Colorado can pose health risks. Mosquitoes, for instance, are the primary carriers of West Nile virus in the state, with human cases typically peaking in August and September. Colorado has experienced severe West Nile virus seasons, including 2023, which saw 634 human cases and 51 deaths, making it the highest in the nation that year. In 2024, the state remained among the top five nationally for West Nile virus cases, and in mid-2025, confirmed human cases and deaths have already been reported. Most individuals infected with West Nile virus show no symptoms, but serious illness can develop, particularly in those over 60 or with underlying medical conditions.
Ticks are another concern, with 27 known species in Colorado. The Rocky Mountain wood tick is the most common tick that bites humans and is primarily active in spring. Colorado Tick Fever (CTF) is the most prevalent tick-borne disease in the state, characterized by flu-like symptoms that can sometimes recur, though recovery is usually complete. Rocky Mountain Spotted Fever (RMSF) is rare in Colorado, typically accounting for only a few cases annually, despite its name. Lyme disease, however, is not endemic to Colorado, as the specific tick species that transmit it are not found within the state, meaning any cases in residents are acquired elsewhere.
The Western black widow is the most common venomous spider in Colorado. Females are identifiable by their glossy black bodies and a distinct red or orange hourglass marking on their underside. While their venom contains a neurotoxin, fatalities from black widow bites in the U.S. have not been confirmed in recent decades. The brown recluse spider is extremely rare in Colorado and is often misidentified, typically only appearing if transported from other regions. Its venom can cause localized tissue damage, leading to a slow-healing ulcer.
Colorado’s Diverse Insect Habitats
Colorado’s varied ecosystems provide a wide array of habitats that support its diverse insect populations. The state’s geography includes arid high deserts, expansive eastern plains, dense forests, and high-altitude mountainous regions. Each of these distinct environments offers unique conditions, such as specific vegetation, moisture levels, and temperature ranges, which influence the types of insects that can thrive there. For example, certain tick species, like the Rocky Mountain wood tick, are primarily found at elevations between 4,000 and 10,000 feet. This ecological diversity ensures a broad spectrum of insect life, with different species adapted to specific regional conditions.
Coexisting with Colorado’s Insects
Interacting safely with Colorado’s insect population involves adopting practical preventative measures. When spending time outdoors, particularly in areas with tall grass or dense vegetation, wearing long sleeves and pants can help reduce skin exposure. Tucking pant legs into socks provides an additional barrier against ticks. Using insect repellents containing active ingredients like DEET, picaridin, or oil of lemon eucalyptus can also deter ticks and mosquitoes. After outdoor activities, it is advisable to conduct thorough body checks for ticks, including clothing and gear, and inspect pets.
While taking precautions against potentially harmful insects, it is also beneficial to recognize the positive roles many insects play in the environment. Many species are crucial for pollination, nutrient cycling, and serving as a food source for other wildlife, contributing to the overall health of Colorado’s natural ecosystems.