Understanding which species migrate and why is critical to elucidating their ecology and planning for their conservation yet studying migration in insects is complicated by their small size and the difficulty of tracking individuals over long distances. In my PhD, I studied the movement patterns of butterflies and assessed global progress in insect conservation. First, I conducted a comprehensive literature review, and discovered that at least 568 butterfly species show evidence of migratory movements. This suggests migration is much more widespread among butterflies than previously realised; indeed, the rate of ‘discovery’ of migratory movements in butterflies suggests that thousands of species are migratory. The geographic distribution of butterfly migration is poorly understood. I built ecological niche models to describe and further investigate migration in migratory butterflies. I discovered strong seasonal variation in habitat suitability for most species, and the greatest rate of apparent migration occurs in the tropics. Several species showed extreme seasonal fluctuations in their distribution, and such species may be at elevated extinction risk. Our climate is changing, including directional changes in temperature, rainfall, and timings of seasonal transitions. We might expect to see changes in migratory behaviour as a consequence. I studied the range expansion of the tawny coster butterfly. I discovered that its climatic niche differs only slightly during its colonisation of Australasia, consistent with changing conditions driving its changed distribution. The species has expanded its range in Australia at an impressive average rate of ~ 135 km/year. Protected areas have been established around the world to preserve samples of biodiversity from pressing threats, yet the adequacy of protected area systems in many tropical nations is poorly understood. I assessed the extent to which butterflies are covered by protected areas in a mega-populated country, Bangladesh. Using three different methods to map species distributions, I found that the current protected area distribution in Bangladesh is inadequate for conserving butterflies, with