First paragraph: Bumblebees belong to the genus Bombus, which comprises about 250 species, largely confined to the temperate Northern Hemisphere. They are wholly dependent on flowers for their energetic and developmental requirements. Most are social species, with nest sizes varying from 50 to 400 workers. As such, they have attracted considerable attention regarding their role as pollinators. There is a growing body of evidence that bumblebees have declined in Europe, North America and Asia in recent decades because of multiple causes probably including habitat loss, impacts of pesticides, competition from non- native species and the introduction of non-native diseases (Goulson, Lye & Darvill 2008a; Williams & Osborne 2009). Recent health problems affecting honeybees and a perception that other pollinators may be declining has led to serious concern that we might be facing a global ‘pollination crisis' affecting pollination of crops and wildflowers (e.g. Aizen & Harder 200