What bit me in Colorado?

16 biting or stinging species have verified records in Colorado. The fastest way to narrow it down is where on your body the marks are and how they are arranged — below the knee in clusters points to fleas or chiggers, lines on uncovered skin point to bed bugs, scattered single bumps point to mosquitoes. Bite season here runs roughly May to September.

Active around now in Colorado

• Honey bee
• Paper wasp
• Bald-faced hornet
• Wolf spider
• Yellow sac spider
• Carpenter ant
• American dog tick
• Bed bug
• Black fly
• Brown recluse spider

Recorded biting species in Colorado

Record counts come from the GBIF biodiversity database and reflect how often a species is reported and identified in Colorado. They are a guide to what is plausible here, not a census — and they say nothing about how likely you are to be bitten indoors.

Bite season month by month

Of the 16 species recorded in Colorado, 16 are active in June — the peak of the local season. The semi-arid highland climate here is what sets those boundaries: species that need warmth disappear at the edges of the year, while the indoor ones do not care.

Narrowing it down in three questions

1. Where on your body? Below the knee in clusters points to fleas or chiggers. Uncovered skin — arms, shoulders, neck — points to bed bugs or mosquitoes. Along a sock line or waistband is close to diagnostic for chiggers.
2. How are they arranged? A line or zigzag of three or more suggests bed bugs. Scattered single bumps suggest mosquitoes. A curved group with white pustules the next day means fire ants.
3. Indoors or outdoors, and when? Bites that appear overnight in one specific bed are a different problem from bites after an afternoon in tall grass. In Colorado the outdoor season runs May to September; the indoor species run all year.

Stings rather than bites in Colorado

Honey bee, Paper wasp, Bald-faced hornet, Carpenter ant, Yellowjacket are recorded here. Stings differ from bites in one way that matters: they can cause anaphylaxis in sensitised people, and that risk does not depend on how bad previous stings looked. Anyone who has had a severe reaction should carry an adrenaline auto-injector.

Species associated with illness here

• American dog tick bite — Rocky Mountain spotted fever, tularemia, tick paralysis (rare, resolves on removal)
• Mosquito bite — West Nile virus, La Crosse encephalitis, dengue (Gulf Coast and Southwest, local cases), chikungunya (rare, travel-linked)
• Lone star tick bite — ehrlichiosis, Heartland virus, tularemia, STARI, alpha-gal syndrome (red meat allergy)
• Scabies rash — secondary bacterial skin infection is common from scratching

Most bites from these species transmit nothing. What matters is the follow-up: note the date of the bite, and report any fever or expanding rash in the following weeks to a clinician, mentioning the bite explicitly.

Year-round in Colorado

Weather does not affect everything. Bed bugs, scabies and head lice depend on people rather than season, so a bite pattern in January in Colorado points to those first — see what is biting me at night.