Insect migrations
Birds don't have the sky to themselves. All manner of insects and other tiny creatures also make impressive journeys through the air. Weaker fliers, such as aphids, simply take off and trust the wind. Some spiders put up silken threads, like tiny parachutes, and drift for miles on the breeze. However, these creatures do not return to the same spot and so their journey’s are not return migrations, like the ones birds make. The insects and spiders simply disperse to make sure that their population is not too crowded. In summer, the air can be thick with these tiny creatures, providing vital food for aerial feeders, such as swallows and swifts. Some strongly flying insects do make return migrations, just like birds. The painted lady butterfly migrates each spring from North Africa to the UK – some getting as far north as Scotland. It returns in autumn to North Africa where it lays its eggs before dying. The next generation of painted ladies then sets off to the UK in spring. The best known migrating butterfly is the monarch from North America. In autumn, as it gets colder, monarchs migrate south. Some travel over 3,000 km (1,800 miles), at an average speed of up to 50 kph (30 miles per hour). They spend winter in Mexico and California, where hundreds of millions cluster on tree trunks in a few special forests. In spring, they mate, before flying north again to lay their eggs. |
