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With dry air and clear skies, people in the west have much greater opportunity to enjoy the light shows at dawn and dusk and celestial phenomena. Following are comments and details, each starting with a question about mechanisms. 

Boulder residents were acutely aware of the wildfires, for they had been breathing smoke since the Pine Gulch fire started near Grand Junction on July 31. But the proximity of the CalWood Fire and the sight of roiling smoke rising and forming pyrocumulus clouds at the northern edge of Boulder brought the terrible threat home.

A minimum of 21 subspecies have been described, usually geographically separated but sometimes with geographic ranges sharing a borderButterflies flitted among flowers beside South Boulder Creek, in Boulder's greenbelt near the town of Marshall.

Prickly poppies are distinguished from other species in the genus Argemone by the lack of spines on the upper sides of leavesPrickly poppies, Argemone polyanthemos, were abundant and in full bloom along the Degge Trail in the greenbelt north Boulder

They are secretive and cryptic, but you can see them if you know what to look forWhat causes those conical divots in the soft, dry soil beneath large conifers in the mountains and at the bases of cliffs on the Colorado Plateau? They presented a

Wielding all of these defenses, these moths have little to fear from birds or bats and they ignore photographers with impunityTriangular leaf senecio, Senecio triangularis, is common on the eastern slope of Cimarron Ridge in the San Juan Mountains,

The colors and patterns of black swallowtails reveal the diversity of evolutionary dynamics acting on the sexes and the various life-history stages

Evolutionary biologists have noted that effective chemical defenses promote gregarious behavior   During fall in the mountains, ladybugs migrate uphill, forming dense overwintering populations, defended by the alkaloids of

Mutations produce new genetic forms all the time, in all species, in all genesAt this time of year, firemoths (Schinia masoni) can be seen on blanketflower (Gaillardia aristata), a colorful native wildflower.   Evolution is the

Reakirt's blue, Echinargus isola, is one of ten species of blue butterflies in the Front RangeReakirt's blue butterflies were moving among the flower heads of white clover in my lawn. I presumed that they were nectaring, but I watched closely