Those Migrating Insects: Why the Skies Are Getting Crowded

Despite the widespread interest in migrating monarch butterflies, other insects migrate, too.

That's way we were excited to see National Public Radio's Nell Greenfieldboyce generate a recent piece on "Bugs Abound: If You Think the Skies Are Crowded, You Have No Idea."

She touched on a newly published study in the journal Science, which found that more than 3 trillion migrating insects fly over south-central England each year. 

More than 3 trillion!

Greenfieldboyce interviewed Hugh Dingle, UC Davis emeritus professor of entomology (not involved in the study) for the piece, published in late December.

Dingle, author of the popular textbook, Animal Migration: the Biology of Life on the Move (Oxford University Press), is one of the world's experts on animal migration.  National Geographic featured Dingle in its cover story on Great Migrations in November 2010.  LiveScience interviewed him for its November 2010 piece on Why Do Animals Migrate?

Dingle agrees that many migrating insects receive little attention. "Certain insects like locusts and the monarch butterfly, have gotten a great deal of attention," he told Greenfieldboyce. "But perhaps because of all that attention on these big charismatic insects, the huge migrations that occur in lots and lots of other insects, all the way down to tiny aphids, are certainly not as well known by the public, and may not even be as well known by scientists."

Indeed, the monarch butterfly is one of those "big charismatic insects."  It's an iconic insect in North America largely because of its long-distance migration to precise overwintering sites in Mexico and subsequent return, Dingle told us last year prior to a UC Davis seminar on monarchs. Short photopriods trigger diapause and fat storage, necessary to support migration "and the butterflies orient using a sun compass synchronized to a circadian rhythm in the antennae. Butterflies head for overwintering sites in North America: Transvolcanics Mountains of central Mexico, and the California Coast, particularly Santa Cruz, Pismo Beach, and Pacific Grove.

And scores of butterfly enthusiasts flock there, too, to admire, photograph and monitor them. It's good to see the increasing human population banding together to help save the declining monarch population.

As for the NPR piece, Greenfieldboyce gave a little press to one of the least publicized insects, the marmalade hoverfly, which she described as a "a small, insignificant-looking creature."

But don't consider the hoverfly "inconsequential." It's not only a long-range migrant that travels at great speeds and for hundreds of kilometers in a single flight, but it's a beneficial bug: it eats aphids and pollinates crops as well as wildflowers. It winters in the Mediterranean but returns to England in the spring.

Check out the paper in Science, "Mass Seasonal Bioflows of High-Flying Insect Migrants," for more information on migrating insects and you'll see why the NPR headlined its piece "Bugs Abound: If You Think the Skies Are Crowded, You Have No Idea."

The researchers' 10-year project of monitoring the migration of large and small insects over the southern United Kingdom yields incredible information. That's why we now know what they know--that 3 trillion of these migrating insects fly the friendly--and not so friendly skies--every year.

It's getting pretty crowded there.