Nature Notebook – Insect Migration

Many people are familiar with the seasonal occurrence of bird migration. Equally well known is the Monarch butterfly migration. Unbeknownst to most are the migration feats of other insects.

Research recently conducted in the United Kingdom led scientists to estimate that trillions of insects migrate. The biomass of the insect bodies was calculated to be 3,200 tons! That was just the UK. One scientist explained that “if the densities observed…are extrapolated to the airspace above all continental landmasses, high-altitude insect migration represents the most important annual animal movement over land, comparable to the most significant oceanic migrations.”

The purposes of the migrations are a mystery. One thought is that the insects migrate to disperse their offspring. Many female green darner dragonflies captured during their autumn migration along the eastern seacoast of the U.S. are pregnant. However, biologists don’t know if the dragonflies head for a specific area to lay eggs or if they just deposit them in any spot along the route. However, many insects become reproductively inactive prior to migrating.

Insect species known to migrate include: butterflies (other than Monarchs), moths, dragonflies (one species moves from southern India to Africa cross the Indian Ocean), damselflies, aphids, large milkweed bugs, hoverflies, ladybugs, aphids, lacewings and some flies.