Insect Olympic Feats Astonish Biologists

Butterflies cross the Atlantic, and
tiny gnats fly over the Pyrenees.

 

For their small size and fragility, easily smashed with a swatter, insects are capable of amazing feats of endurance. Here are two examples in the news worthy of a Wow! expression.

Non-stop flight: in a world-first, researchers map a 4,200 km transatlantic flight of the Painted Lady butterfly (University of Ottawa, 25 June 2025). Many Americans have seen “painted lady” butterflies. They’re pretty small as butterflies go, flittering around fields in America, Britain and mainland Europe. Their long-distance migrations have come to light in recent years— among the longest of any known butterfly.

Researchers cannot tag them like they can the larger monarch butterflies, the usual heroes of long-distance migration (see Illustra’s documentary film Metamorphosis, or this excerpt at TheJohn1010Project.com). And yet it has come to light that the smaller painted lady flies even farther than monarchs on their annual migrations, from Europe to Africa and back.

Now, researchers at the University of Ottawa determined that some painted ladies found in French Guiana in 2013, not native to South America, must have flown over from West Africa—a distance of 4,200 km (2,600 miles) over open ocean. This is an astonishing discovery.

“We usually see butterflies as symbols of the fragility of beauty, but science shows us that they can perform incredible feats. There is still much to discover about their capabilities,” emphasizes Roger Vila, a researcher at the Institute of Evolutionary Biology (CSIC-Pompeu Fabra University) and co-author of the study.

The scientists used indirect methods to determine where the insects came from. Pollen studies and genetic comparisons indicated that they started in Europe, made it to West Africa, and then flew across the ocean, making the transatlantic flight in 5-8 days. Even if well fed when they departed, they could not have stored enough fat for energy to make it, so favorable trade winds undoubtedly helped them along the way. Still, that is a long time to hold wings outstretched through nearly a week of nonstop flying.

This finding indicates that natural aerial corridors connecting continents may exist, potentially facilitating the dispersal of species on a much larger scale than previously imagined.

“I think this study does a good job of demonstrating how much we tend to underestimate the dispersal abilities of insects. Furthermore, it’s entirely possible that we are also underestimating the frequency of these types of dispersal events and their impact on ecosystems,” comments Megan Reich, a Postdoctoral Fellow at the University of Ottawa who also coauthored the study.

The work was published in Nature Communications today (June 25, 2024). The authors were pretty amazed at what they found.

The LDD [long-distance dispersal] event by painted lady butterflies documented here covered at least 4200 km across the ocean and is among the longest demonstrated to date for individual insects. With the possibility of an origin in Western Europe, this journey could extend to 7000 km or more – a remarkable feat for a small-sized organism weighing less than a gram. A few other insects are also known to be able to endure LDD. For example, the dragonfly Pantala flavescens apparently migrates annually across the Indian Ocean. The monarch butterfly (Danaus plexippus) also annually migrates between Canada and Mexico, and tagged individuals have demonstrated flights as long as 4635 km (2880 miles). Recent work using light aircraft and individual radio tracking of death head’s hawkmoths (Acherontia atropos) recorded a remarkable maximum ground speed of 69.7 km/hour (19.4 m/s). These scattered reports of individual feats of migration both in terms of distance covered and flight speed are important: collectively they indicate that trans-oceanic LDD events may be sufficiently frequent to have played an underestimated role in biogeographic dispersal over time….

The press release indicates that smaller insects might hitchhike on dust blown across the Atlantic from Africa.

The Saharan air layer is emphasized by researchers as a significant aerial route for dispersion. These wind currents are known to transport large amounts of Saharan dust from Africa to America, fertilizing the Amazon. This study now shows that these air currents are capable of transporting living organisms. 

See my articles at Evolution News about insect migrations, and  dust dispersal of microbes, and another amazing migration story in Australia, featuring a little gray moth.

Millions of insects migrate through 30-metre Pyrenees pass (University of Exeter, 17 June 2024). Though not matching the painted lady story for distance, this feat stands out for sheer insect mass.

Over 17 million insects migrate each year through a single mountain pass on the border between France and Spain, new research shows.

University of Exeter scientists studied migrating insects in the Pass of Bujaruelo, a 30-metre gap between two high peaks in the Pyrenees.

The team visited the pass each autumn for four years, monitoring the vast number and variety of day-flying insects heading south.

The findings for this single pass suggest that billions of insects cross the Pyrenees each year, making it a key location for many migrating species.

Most common were marmalade hoverflies, only 9-12 mm in length, but there were others, including tiny gnat-sized grass flies barely 3 mm long. Researchers also saw house flies and cabbage white butterflies.

“These insects would have begun their journeys further north in Europe and continued south into Spain and perhaps beyond for the winter.

“There were some days when the number of flies was well over 3,000 individuals per metre, per minute.”

Team leader Dr Karl Wotton said: “To see so many insects all moving purposefully in the same direction at the same time is truly one of the great wonders of nature.”

Should people care about insect migrations? Yes, the scientists say. Insects are “hugely important for our planet.”

Nearly 90% of the insects were pollinators and, by migrating, move genetic material great distances between plant populations, improving plant health.

Marmalade hoverfly (Episyrphus balteatus), an important pest controller. From Wiki Commons.

Some of the insects were pest species but many were pest controllers, including the marmalade and pied hoverflies that eat aphids during their larval stage.

Many play a role in decomposition, and all transport nutrients such as phosphorous [sic] and nitrogen large distances, which could be important for soil health and plant growth.

The paper in the Proceedings of the Royal Society B (12 June 2024) calls these insects “the most remarkable migrants of all” due to their sheer abundance. The scientists estimate over 300 pounds of biomass per season traverses this route. When tailwinds are present, the insects can rise over 3000-meter-high mountains through the pass.

The paper does not state the probable distance traveled by an individual insect on the annual migration, but most likely it amounts to well over a thousand kilometers from western Europe, including the UK, into Spain. Perhaps the young make the return trip but the paper did not say. If so, like monarchs, the information on the route must be stored in memory maps in the brain inherited from one generation to the next.

Another wonder of nature comes to light by careful observation. I doubt that human engineers will ever devise robots this small that can fly this far, living off the energy available on the ground, while being able to repair themselves, pollinate flowers, and carry on their missions for months at a time. And I really doubt that human-designed robot craft will ever be able to lay eggs that hatch and do the same, carrying on their functions for numerous successive generations for thousands of years! Could they equip them with sensors like compound eyes and sensitive antennae and jointed legs and flapping wings? And could they paint them with such brilliant colors and patterns as well?

The Lord installed supply chains for our planet’s biosphere: some nonliving (such as volcanoes, wind, and meteoritic dust), and some living, like these insects who “transport nutrients such as phosphorus and nitrogen large distances.” Like truckers and ships, billions of tiny motorized vehicles take part in distributing supplies to needy ecosystems. They also give human researchers an endless supply of wonders to investigate.

Darwinism apparently did not help these biology projects at all. David Lack of “Darwin’s finches” fame and his wife first observed the Pyrenees migration of insects in October 1950, and published the findings the following year, but I could not find if he attributed it to evolution. One co-author from the Institute of Evolutionary Biology in Spain worked on the painted lady butterfly project, but didn’t have anything to say about evolution. I should think any evolutionist witnessing such phenomena would be embarrassed to include that in their CV.