Why is Lepidoptera the second-largest insect order after beetles?

With approximately 180,000 known species, Lepidoptera (butterflies, moths, and skippers) is the second-largest order of insects, surpassed only by Coleoptera (beetles).12

The order's immense diversity is largely attributed to its evolutionary history and ecological adaptability. As the Lepidoptera evolved, they developed specialized feeding mechanisms, such as the proboscis, which allowed them to exploit a wide range of food sources, including nectar and plant juices, as flowering plants diversified. Concurrently, their larvae evolved diverse strategies to feed on various seed plants, allowing them to occupy numerous ecological niches.1

This evolutionary success is further supported by a complex life cycle—consisting of egg, larva, pupa, and adult—and a wide array of defense mechanisms, including camouflage, mimicry, and chemical toxicity, which have enabled them to thrive in diverse environments. Their current species count is so significant that it is more than two and a half times greater than that of all known vertebrates combined.123