Published: Oct. 5, 2018 By

Remembering the profusion of flowers in the previous year, I returned to the White River Plateau this August to photograph wildflowers and their pollinators.

When I arrived at the campground at Deep Lake, I was stunned and disappointed. Instead of meadows bright with flowers, I saw one healthy aster and a paltry, diffuse population of spent flowers.


Pollinators congregate on some of the remaining flowers in a meadow. Click on image or on this link to see larger image. Photo by Jeff Mitton.

After considering my options for several minutes, I decided to test an optimistic hypothesis. If one healthy flower remains in a large meadow, and if pollinators are still foraging for either nectar or pollen, then all of the pollinators must converge on the same flower.

The bright, robust plant still in bloom was a dwarf golden aster, Heterotheca pumila, almost three feet across, slightly over one foot tall, with hundreds of blooms. It thrives on rocky sites in the subalpine and alpine predominantly in Colorado with minor range extensions into Wyoming and New Mexico.

This last flower had, indeed, collected a large population of pollinators — the insects were constantly moving so the aster seemed to be seething. I was intrigued with the diversity of species.

The species that first caught my eye was the largest and most colorful, Edwards fritillary, Speyeria edwardsii. Wingspans ranged from 2.5 to 3 inches, and above the wings were orange with white spots and black markings, while below the wings had numerous large silver spots on a gray-green background. A few were in moderate condition, but most were faded and tattered, showing their age.

Next I noticed about a dozen small butterflies, grey with dark markings on the ventral side of the wings, and blue on the dorsal side. I mistook these for one of the blues, but found that these were blue copper butterflies, Lycaena heteronea. The males are bright blue on the dorsal side while females are light brown. Some of the blue coppers were very old, for their wings were torn and missing substantial fragments, usually a sign of a close encounter with an avian predator. But others were in excellent condition with bright colors. I suspect that two cohorts were flying at the same time.

Another conspicuous group was the tachinid flies, which are large, robust, noisy flies with prominent bristles. They are mimics of bees, and that resemblance protects them from predators. Two species were present, one with a large, bright orange abdomen, and the other predominantly black with a reddish brown stripe on the thorax. Tachinid flies are frequently seen searching flowers but not stopping to sip nectar — they are searching for caterpillars or larvae of a wide diversity of species of butterflies, moths and grasshoppers to inject their eggs onto or into. When the eggs hatch, larvae consume the caterpillar.

Moths were abundant, and while they all looked similar, multiple species might have been in attendance. They were shades of grey with darker lines and light areas — very cryptic. One of the moths was a miller moth, Euxoa auxiliaris, while others were in the same genus. We call them miller moths because their wing scales are easily removed so that the scales litter surfaces like flour covers surfaces in a mill and the clothing of people milling flour. Occasionally hordes of miller moths move off the mountains to nearby towns.

The most abundant group of insects moving among the blooms was solitary bees, which do not store honey and therefore are not defensive and almost never sting. Some were in the family Megachilidae, which includes leafcutter, mason and resin bees. They carry pollen in a pouch on the underside of the abdomen rather than in baskets on the legs. These were relatively large, but still smaller than honeybees. Smaller, distinctly slender bees were in the family Halictidae, called sweat bees for their attraction to droplets of sweat.

In addition, I saw some beetles and some other insects, but could not identify them. 

I really enjoyed this tiny hotspot of species diversity and came away with two thoughts. On the positive side, many of these pollinators were fueling up to continue mating or to deposit more eggs. On the melancholy side, I suspected that some of these insects could fly to lower elevations to find more flowers, but for most the distance to the next filling station was too far.