A country built on small things

Costa Rica occupies less than 0.03% of Earth’s surface — yet it shelters an estimated 5% of the planet’s biodiversity. Insects lead that count by a wide margin. Entomologists working in the country have already described more than 300,000 species, and consensus among researchers is that at least twice that number are still waiting to be named.

That density means every trailhead is a working laboratory. A ten-minute pause at a fruiting fig can produce more insect species than most temperate biologists see in a year. Below are seven of the most spectacular — the ones worth planning a trip around.

1. Blue Morpho Butterfly (Morpho peleides)

The most photographed insect in Central America, and rightly so. A wingspan of up to 15 cm and dorsal wings that produce an unnatural, mirror-bright blue — not a pigment, but light scattering off microscopic ridges on the scales. In flight through a forest patch of dappled light, it flashes on and off like a signal.

Where to look: forest edges and clearings, especially near fruit falls where males gather to feed on fermenting fruit.
Best time: late morning, dry season (December–April) for peak activity.
Field note: the wing undersides are camouflage — cryptic browns with big eyespots. That’s why they seem to “vanish” when they land.

2. Leaf-cutter Ants (Atta cephalotes)

The most sophisticated agricultural civilization on Earth outside of humans. Colonies of up to eight million individuals harvest leaf fragments — following pheromone highways that can be 30 m long — not to eat, but to feed a fungus they farm in underground chambers. That fungus is their only food.

Where to look: along any lowland forest trail. Watch for a moving line of green flecks crossing the path.
Best time: anytime — activity is 24/7.
Field note: the soldiers guarding the trail are 200 times the mass of the smallest workers. Same colony, same DNA — different diet in the larval stage.

3. Hercules Beetle (Dynastes hercules)

The largest beetle in the New World, and one of the strongest animals on Earth relative to body weight — it can lift 850 times its own mass. Males carry a curved thoracic horn that can be as long as the rest of the body, used in duels over rotting logs where females lay eggs.

Where to look: mid-elevation cloud forest (Monteverde, Braulio Carrillo). Attracted to lights at night.
Best time: May to August, wet season nights.
Field note: harmless to humans. Handle with a light touch — those legs grip like fishhooks.

4. Bullet Ant (Paraponera clavata)

The most painful sting of any insect on the planet, according to Justin Schmidt’s famous pain index (4.0+ out of 4 — “walking over flaming charcoal with a three-inch nail embedded in your heel”). About 2.5 cm long, jet black, and solitary foragers on tree trunks.

Where to look: lowland Caribbean rainforest, on the trunks of large canopy trees.
Best time: nocturnal.
Field note: observe from a respectful distance. Their scientific name literally means “near ant” — evolutionarily, they aren’t even that closely related to other ants.

5. Glasswing Butterfly (Greta oto)

Its wings are literally transparent. No pigment, no scales — just a thin membrane over veins. In flight it looks like an animated pane of glass. A predator defense strategy taken to its logical extreme: if you can’t be seen, you can’t be caught.

Where to look: mid-elevation cloud forest, feeding on Lantana and Cestrum flowers.
Best time: mornings between 8–11 am, dry season.
Field note: males cluster in groups to feed on toxic plants — the alkaloids protect them from predators and boost their sex appeal.

6. Jewel Scarab (Chrysina spp.)

Living metal. Species in the genus Chrysina come in mirror-polished gold, silver, and green — the result of layered chitin that reflects circularly polarized light. Held in your palm they look like jewelry, not animals. Costa Rica hosts around 15 species, most in cloud forest.

Where to look: Monteverde, San Gerardo de Dota, and other cloud-forest sites — often on oak and myrtle foliage.
Best time: May to July.
Field note: the reflective coating may confuse predators by mimicking water droplets. Nobody is sure yet — new hypotheses appear every few years.

7. Owl Butterfly (Caligo memnon)

Large, dull-brown, and unassuming — until it opens its wings and reveals two enormous eyespots that mimic the face of an owl. Predators that were about to strike think twice. A masterclass in evolutionary mimicry.

Where to look: low, shaded forest edges and banana plantations (their larvae feed on Musa).
Best time: dusk — they are crepuscular, more active at low light than other butterflies.
Field note: when they flap slowly, the eyespots wobble — the movement mimics a blinking owl more than a static one.

How to observe insects responsibly

Three rules that protect both the insects and the ecosystems they depend on:

• Do not collect. Photography is enough. Costa Rica strictly regulates insect collection — permits are required and rarely issued to tourists.
• Watch, don’t handle. Even harmless species are fragile. Wing scales rub off with every touch.
• Skip the flash. Nocturnal insects are disoriented by bright lights. Use a low-lumen red headlamp for observation and a diffused flash only when the photo really justifies it.

Best season for insect watching

Dry season (December to April) is best for daytime butterfly diversity — clear mornings mean maximum activity. Wet season (May to November) is peak time for beetles, moths, and any species attracted to lights at night. Cloud forest sites like Monteverde and San Gerardo de Dota host unique high-elevation communities year-round.

Ready to see them yourself?

Our small-group expeditions in Costa Rica are led by expert naturalists with a specific eye for the small stuff. Macro photography sessions available on request. Limited spots each season. See upcoming Costa Rica tours →