Some butterflies are able to fly across huge distances. One of the most accomplished travelers is the American monarch, which leaves North America in the autumn and lies to Mexico where it spends the winter. The first three or four generations that hatch during the summer stay in the north where they mate, but the last generation to emerge before the autumn does not become sexually mature, although it will have well developed flying muscles. These butterflies then embark on a long journey, flying more than 3000km in eight to 12 weeks. The insects travel on average a distance of 70 km per day, but with favorable winds they can over as much as 300km or more. They use the positions of the Sun for navigation. In the spring, these creatures embark on the return journey north, during which they reach sexual maturity and lay their first eggs. Once they have laid their eggs a lot of females die, as do many males. Their descendants continue a journey that is completed in many stages and often takes several generations. On the descendants of butterflies that set off from the north eventually return to their original home.