Mayfly Nation

If you want to find the most species of wildlife, go to the tropics, a fact well known among conservation biologists for years. Tropical habitats favor diversity more so than temperate climates.

To give one example: Colombia, where I just spent a month, may not be the largest country on earth, but it leads the world in the number of species of vertebrates, birds, amphibians and butterflies.

One reserve in Peru, Manu National Park in the Amazon Basin, has more bird species than the entire United States.

The United States may be a big country, but it doesn't have the most species. Unless you're talking about mayflies.
The United States has more than 600 species of mayflies, more than any other country.

It's truly mayfly nation: A fact well appreciated by fly fishers, but perhaps less so by other nature lovers. The adult mayfly is a beautiful, delicate insect with a fascinating life history. When a major hatch is occurring (as above), it's one of nature's finest spectacles, even if you don't fish.

Mayflies live as underwater nymphs for a full year, hatching (often en masse) to become winged adults. As they take flight, the mayfly's journey is coming to an end: An adult mayfly only lives from 30 minutes to a day before it breeds, lays eggs and dies.

As such, adult mayflies only have vestigial mouths, and their digestive tracts are filled with air.

Mayfly hatches can reach truly staggering proportions: Along some of the Great Lakes, snow plows clear them off the streets. They can literally blanket the surface of a stream (see Silver Creek intern Ryan Urie's photo below of a brown drake hatch, from an earlier blog post).

I remember once standing along Penns Creek in Central Pennsylvania, listening to an evening hatch of Eastern green drakes: So many were in the air, it sounded like the wings of geese beating overhead.

Silver Creek has some of the finest mayfly hatches in the country, with the brown drake (early June) and trico (July and August) being particularly famous. Those hatches are one of the reasons Silver Creek has so many trout. If you visit now, you should be able to see scattered fall hatches, especially the small olive Baetis.

Mayflies may exist in huge numbers and varieties, but they do have one requirement: Clean water. A polluted stream is quickly cleared of its mayflies. Fortunately, efforts to clean water supplies over the last few decades have meant a resurgence in mayflies in areas where they had disappeared--like the Great Lakes. As long as this commitment to clean water remains, the United States will likely remain as the capital of mayflies. --Matt Miller