Newfound Understanding of Insect Migration

Their Behavior and Activities are More Complex Than Realized

Oct 17, 2009

Migrating insects return to the same wintering locations while they fuel, rest, and use routes and flight patterns that are similar to those used by birds.

Many studies on insect migration have focused on searching for innate compasses and maps that these tiny migrants may have genetically wired into their brains. Researchers have noted that insects use the same behavioral methods and follow the same pathways as birds during their migrations. New thinking on the matter suggests it may be birds that follow the same pathways the insects use because the insects may provide the fuel for the birds.

Which Insects Migrate

People have known about the movements of migratory locusts since Biblical times. Migratory movements of the monarch butterfly (Danaus plexippus) into California have been observed for over one hundred years, but little was known about why they moved, what forces drove them, or how they found their way, and the even more impressive migration between Canada and Mexico was not recognized until 1976 when Fred Urquhart found the wintering areas in oyamel forests in the mountains southwest of Mexico City. With the understanding of the monarch migrations, came awareness of migrations of other butterflies: in North America: common buckeye (Junonia coenia), painted lady (Vanessa cardui), American lady (Vanessa virginiensis), red admiral (Vanessa atalanta), cloudless sulfur (Phoebis sennae), sachem (Atalopedes campestris), question mark (Polygonia interrogationis), clouded skipper (Lerema accius), fiery skipper (Hylephila phyleus) and mourning cloak (Nymphalis antiopa).

The migratory movements of the green darner (Anax junius) are most well known and studied, but other species migrate: eastern pondhawk (Erythemis simplicicollis), blue dasher (Pachydiplax longipennis), black saddlebags (Tramea lacerata), twelve-spotted skimmer (Libellula pulchella), spot-winged glider (Pantala hymenaea), wandering glider (Pantala flavescens), and calico pennant (Celithemis elisa).

Bees and wasps can migrate, but their migrations are usually local and often altitudinal rather than longitudinal: moving up mountains in the spring and down into valleys in the fall. African “killer” bees (Apis mellifera scutellata) are expanding their range in North America in what some call a migration, but this is a range expansion rather than a true migration.

Migratory Behaviors

Insect behaviors while preparing to and actually migrating are often similar to those of birds. Prior to migration, the insects gorge and put on weight to provide the energy needed for flying. Migratory flights usually occur after cold fronts move through or during periods of extended windy weather. If insects fly on one day, they normally rest or feed on the next unless moving across inhospitable regions. When possible, migratory insects soar like albatrosses and vultures rather than using powered flight. Yet, if wind direction is other than the flight direction, insects are able to both use strong flight and tack across the wind to make headway.

By placing micro radio transmitters on dragonflies Martin Wikelski found that they sometimes reverse their flight direction if they encounter large bodies of water to cross – much as birds do.

Researchers often state that insects use the same paths and behaviors that birds do. Since dragonflies have been on the planet since the Carboniferous Period (about 325 million years ago) and birds only began flying in the Jurassic (about 120 million years ago), it is more likely birds developed migratory behaviors by following insect swarms than the reverse. By following migratory insects, birds would be ensured food to refuel along the way.

Although butterflies usually refrain from mating during migration and in their wintering locations, dragonflies and locusts often mate and lay eggs along their migratory path. Dragonfly larvae live in water and are less affected by low temperatures than are terrestrial larvae, and since adult dragonflies do not live as long as adult butterflies, breeding in winter habitats ensures a fresh generation to make the return flight. Butterflies resume reproductive activity during the northward migration, and the new generation(s) produced along the spring and summer paths complete the migratory circuit.

Locusts do not migrate to escape inclement weather, rather they move to find new food sources. By laying eggs during the migration, leaving offspring along their path allows for range expansion and increased population sizes.

Although a large dragonfly or butterfly weighs only three or four grams, these featherweights can migrate several thousand miles to the same locations and even same trees their ancestors flew to a year earlier. The way they do this is still only partially worked out, but investigators are making great strides toward understanding the intricacies of insect migration.

The copyright of the article Newfound Understanding of Insect Migration in Insects/Spiders is owned by Albert Burchsted. Permission to republish Newfound Understanding of Insect Migration in print or online must be granted by the author in writing.