Butterfly populations peak in July across the Open Space system. On just about any hike you’ll notice many different species, like the Anise Swallowtail pictured above. Butterflies are most active on warm days. They often congregate in flower-filled meadows and in low-lying muddy areas where small streams cross trails.

But if you really want to see a butterfly show, head to the top of one of Boulder’s mountains on a warm afternoon. Many butterflies engage in hilltopping: as the day progresses, they fly up slope. A mountain peak is like a funnel in reverse - as the butterflies move upwards, the topography concentrates them all at the summit. This may help them find mates, but it will also help you find oodles and swarms of butterflies. Grab your camera and head for the top of Green Mountain!

Butterflies feed on nectar which they gather from flowers with their long, hollow tongue or proboscis. They keep the tongue rolled up in a tight coil while flying. When a butterfly alights on a flower to feed, special muscles at the base of the proboscis force high pressure fluid into the tongue, causing it to elongate. The butterfly can then probe the depths of a flower in search of nectar, much like a kid slurping the dregs of a soda bottle with a long straw.

The Front Range has the fourth highest biodiversity of butterfly species in the United States! Butterflies are a quick and dirty indicator of overall biodiversity: since the larvae are very picky about which plants they eat, you can estimate how diverse the plant community is by  observing how many kinds of butterflies you find.   Tiger Swallowtails are the big black and yellow butterflies that visit gardens and back yards. Pale Swallowtails are their cream-colored cousins. Weidemeyer’s Admirals are handsome dark chocolate brown butterflies with prominent white wing bands; look for them in wooded canyons and shrubby gulches. Many kinds of orange-brown fritillaries may be seen nectaring in patches of wildflowers.  

This Snowberry Clearwing is a harmless, plump little moth that mimics a stinging bumblebee (yellow & black warning stripes, clear wings) to scare off predators. But unlike bees, they can hover at flowers to extend a straw-like proboscis for nectar.

Mimicry is everywhere - just look in your garden for examples. The Anise Swallowtail in the previous picture has tails and spots on its hind wings, mimicking a fake head with an eye and antennae. When a bird tries to snatch up the butterfly, it strikes for the head…which isn’t real. The butterfly escapes in an unexpected direction.

Fake eye spots are also found on the hindwing of some drab moths. When at rest, the moth pretends to be tree bark with brown speckled colors; but if it’s startled, it flashes its big eyespots. For an instant it looks like an owl or other dangerous predator, giving it a chance to fly off.

Many of the bees and wasps you see are actually harmless flies with black and yellow colors. By resembling something with a sting, they avoid becoming a tasty snack.