Episode 203: Swarms!

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Thanks to Nicholas and Juergen for their suggestions! Let's learn about some insects that migrate and swarm! Further listening: The Animal Migrations Patreon episode (it's unlocked so anyone can listen) Further reading: Ladybugs Are Everywhere! Monarch butterflies gathered in winter: The painted lady butterfly: The bogong moth: The globe skimmer dragonfly: Ladybugs spend the winter in bunches, sometimes in your house: A stink bug, one of many potentially in your house: This person is not afraid of locusts even though I would be freaking out: A field in Australia being eaten by locusts (the brown part): Show transcript: Welcome to Strange Animals Podcast. I’m your host, Kate Shaw. Let’s learn about some insects this week, but not just any old insects. Let’s learn about insects that swarm. Thanks to Nicholas and Juergen for suggestions that led to this episode! Nicholas suggested long-distance migrators ages ago, and I did do an episode about migration for a Patreon episode. I’ve unlocked that episode so anyone can listen to it, with a link in the show notes. I’ve also used some of the information in that episode for this one, specifically the part about monarch butterflies. In fact, let’s start with the monarch butterfly. The monarch is a good-sized butterfly, with orange and black wings with white spots along the edges and a wingspan of up to four inches, or 10 cm. It lives in many parts of the world, but only the North American subspecies of monarch migrates. Every autumn, monarch butterflies living in North America, where they breed, head south to winter in the mountains of central Mexico, a trip that can be as long as 3,000 miles, or 4,800 km. They spend the winter in oyamel fir trees, millions of butterflies in the branches. When spring arrives, the butterflies head north again, but they don’t get all the way back to their original range. If they’re lucky, they reach Texas, where they mate and lay eggs on milkweed plants before dying. The caterpillars hatch, eat up the milkweed, spin cocoons, and emerge transformed into new butterflies that continue the flight north, deeper into North America. But those butterflies don’t make it all the way to their parents’ home range either. They too stop to mate, lay eggs, and die. It can take four or five generations for monarch butterflies to reach Canada and other distant parts of North America, and by that time it’s autumn again. The butterflies fly back to Mexico. Butterflies heading north live out their entire life cycle in only five or six weeks, but the butterflies that return to Mexico live up to eight months. Researchers think the northward migration follows the blooming of milkweed plants. Milkweed contains toxins that make the monarchs poisonous to a lot of animals, but some birds and a lot of insects will eat the caterpillars. Some populations of North American monarchs overwinter in California, Arizona, or Florida instead of Mexico. The North American monarch is declining in numbers, probably mostly due to the decline of milkweed. The best way to help the butterfly is to plant milkweed in any area you don’t want to mow very often. While the monarch migration is astounding, it’s not the only butterfly that migrates. A small, pretty butterfly called the painted lady lives throughout much of the world, even the Arctic, but not South America for some reason. Some populations stay put year-round, but some migrate long distances. One population winters in tropical Africa and travels as far as the Arctic Circle during summer, a distance of 4,500 miles, or 7,200 km, which takes six generations. The butterflies who travel back to Africa fly at high altitude, unlike monarch butterflies that fly quite low to the ground most of the time. Unlike the monarch, painted ladies like many kinds of flowers, not just one plant, and they don’t always migrate every year. In Australia,

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