Costa Rica’s bugs are noticeable but manageable for most travelers. The country sits in the tropics, so insects are more abundant and diverse than in temperate climates, and a handful of species bite, sting, or carry disease. But the reality is far less dramatic than many travelers fear. With basic precautions, bugs rarely ruin a trip.
The Biting Insects You’ll Actually Encounter
Mosquitoes are the most common nuisance insect across Costa Rica, active in lowland and coastal areas especially around dawn and dusk. They range from mildly annoying to a genuine health concern depending on the region and season. Beyond mosquitoes, the main biting pests include midges (tiny flies sometimes called “no-see-ums”), chiggers, ticks, and sand flies. Wasps are also present but generally only sting when disturbed.
Chiggers deserve special mention because they catch many visitors off guard. These microscopic mites live in tall grass and brush, latching onto skin and causing intensely itchy red welts that can last for days. You won’t feel them at the time. Tucking pants into socks and applying insect repellent to your ankles and waistband before hiking through grass is the simplest prevention. Sand flies, found along some Pacific and Caribbean beaches, leave small bites that itch disproportionately to their size.
Mosquito-Borne Disease Risk
Dengue fever is the primary mosquito-borne disease concern. Costa Rica has reported over 392,000 dengue cases since the virus first appeared there in 1993, and transmission continues year-round. In 2024, the country saw a significant surge, with the Ministry of Health confirming 27,184 cases by late October alone. Dengue-carrying mosquitoes bite during the daytime, so repellent isn’t just an evening precaution.
Chikungunya arrived in 2014 and Zika in 2016, both spread by the same daytime-biting mosquito species. Cases of both still occur but at lower levels than dengue. Malaria transmission is limited to specific areas: Alajuela Province near the Nicaraguan border and parts of Limón Province on the Caribbean coast. If you’re staying in the Central Valley, popular tourist beaches, or cloud forest destinations, malaria is not a practical concern.
DEET-based repellent (25% or higher concentration) applied to exposed skin, along with lightweight long sleeves during peak mosquito hours, significantly reduces your risk for all of these. Permethrin-treated clothing adds another layer of protection for jungle hikes or rural stays.
Spiders, Scorpions, and the Bullet Ant
Costa Rica is home to 14 species of scorpions. The most commonly encountered one delivers a painful sting comparable to a wasp, but scorpion stings in Costa Rica are not considered deadly to healthy adults. They tend to hide in shoes, under towels, and in dark crevices, so shaking out clothing and footwear before putting them on is a reliable habit to build, especially in rural lodges.
The bullet ant is the insect that gets the most dramatic reputation. Found throughout Costa Rica’s tropical forests, it ranks at the top of the Schmidt Pain Index, a scale that rates insect sting pain. Its sting has been compared to being shot, producing waves of burning pain that can last a full 24 hours. The venom contains a neurotoxin that affects the central nervous system, which is why the pain radiates so far beyond the sting site. That said, bullet ants are large (about an inch long), slow-moving, and easy to spot. They primarily travel high in the forest canopy and nest in tree bases. Encounters happen most often when hikers lean against a tree or grab a branch without looking. They are not aggressive unless provoked.
Venomous spiders exist in Costa Rica, including wandering spiders and brown recluses, but bites are rare. Spiders avoid human contact, and most species you’ll see in lodges and bathrooms are harmless.
Where Bugs Are Worse (and Better)
Bug density varies dramatically depending on elevation, climate, and proximity to standing water. The hot, humid lowlands on both the Caribbean and Pacific coasts have the highest concentrations of mosquitoes, sand flies, and biting midges. Coastal towns like Manuel Antonio, Tortuguero, and the Osa Peninsula are beautiful but buggy, particularly during the rainy season from May through November.
Higher elevations offer real relief. The Central Valley, where San José sits at roughly 1,100 meters, has noticeably fewer biting insects. Cloud forests like Monteverde are cooler and historically too wet and cold for many lowland pests. Interestingly, research from the Área de Conservación Guanacaste has documented that cloud forest conditions are shifting: the cloud layer now sits 100 to 500 meters higher than it did in the 1980s, and some insects like ants have moved into elevations where they were previously absent. But for travelers, cloud forest destinations still mean far fewer mosquitoes and biting flies than the coast.
Dry forest areas in Guanacaste Province fall somewhere in between. The dry season (December through April) brings fewer insects overall, while the wet season ramps up mosquito breeding habitat considerably.
Practical Ways to Minimize Bug Problems
- Repellent: Apply DEET or picaridin repellent to exposed skin, reapplying every few hours. Natural alternatives like oil of lemon eucalyptus work but require more frequent application.
- Clothing: Light-colored, loose-fitting long sleeves and pants reduce exposed skin. Bugs are more attracted to dark colors. Treating clothes with permethrin before your trip provides protection that lasts through several washes.
- Timing: Mosquitoes peak at dawn and dusk, but dengue-carrying species also bite midday. Sand flies are worst in the late afternoon on beaches.
- Accommodation: Screened windows, air conditioning, and bed nets (if provided) make a significant difference at night. Higher-end lodges in buggy areas typically have good screening.
- Footwear: Closed-toe shoes on forest trails protect against chiggers, ticks, and ground-dwelling insects. Shake out shoes each morning.
Most travelers who visit Costa Rica come home with a few mosquito bites and nothing more. The bugs are real, and the tropical species are more diverse than what you’d find in North America or Europe, but they’re a manageable part of the experience rather than a reason to reconsider the trip. Packing good repellent and choosing your wardrobe wisely on hiking days handles the vast majority of the problem.