Analyze This: A massive annual insect migration

Trillions of tiny travelers in the sky add up to a massive migration

Scientists tallied all the ladybugs (seven-spotted species shown) and other high-flying insects and their kin that travel over the United Kingdom each year. This may be part of the biggest migration of land animals on the planet.

LEVIATHAN1983/WIKIMEDIA COMMONS (CC BY-SA 3.0)

By Lillian Steenblik Hwang

June 13, 2017 at 6:00 am

Spring in the Northern Hemisphere is time for what may be part of the biggest migration of land animals on the planet. Look up! An invisible insect migration could be taking place overhead.

Scientists recently finished a 10-year study of insect migrations in the southern part of the United Kingdom. Some 3.5 trillion aphids, moths, flies and other arthropods (including spiders) were migrating high overhead each year. The total weight of all those critters flying over the United Kingdom alone is equivalent to some 30 blue whales swimming high in the sky.

Migrations of insects do not look the same as bird migrations. Birds usually make roundtrip flights — from one location to another and back — each year. Insects have much shorter lives. As a result, their migrations usually are a one-way trip from their home to a new destination. The next generation of insects might make a return trip back to their parents’ home — or just to the next stop on some journey.

Insects would seem to be at mercy of the wind. But scientists showed medium-size and larger insects could migrate seasonally in the same direction, regardless of wind direction. Perhaps these animals have specialized body parts that give them an advantage when flying against the wind, the researchers now speculate.

Insects are a fundamental part of many ecosystems. Having a better understanding of how and where they move can help scientists learn more about the animals that depend upon them, such as songbirds.

Each circle indicates direction of migration in the same way that a compass does. Arrows indicate average migration direction. So the leftmost circle shows a migration generally to the northeast. Insects of medium or large size (center and rightmost circles, respectively) were able to travel in the direction they chose. Many flew northwest in spring (middle and right circles). The majority of the insect migrants were tiny and did not travel against the wind, as indicated by the bulge in black dots surrounding the leftmost circle (representing a mass migration).G. HU ET AL/SCIENCE 2016

Data Dive:

Approximately what percentage of large insects traveled west?

In what direction did the largest percentage of medium-size insects travel?

Based on the data presented in this figure, if you studied the direction that 500 medium-sized insects migrated in spring by day, about how many would you expect to travel northwest? Approximately how many would you expect to travel east?

What do you think about how the researchers presented their data in this visualization? What is easy to understand? What is confusing?

How else might you present these data?

Analyze This! explores science through data, graphs, visualizations and more. Have a comment or a suggestion for a future post? Send an email to sns@sciencenews.org.