Yesterday my husband asked me if I knew that some moths migrate. I hadn’t really thought about it but decided it sounded probable, as I knew butterflies migrated and moths and butterflies belong to the same order, Lepidoptera.
Then he asked me which would migrate most speedily – birds or moths. Logically, at least as far as logic exists in my brain, I thought it must be moths – they’re lighter and smaller – but in fact birds and moths take the same amount of time to travel.
Night-flying moths match birds in efficient speed and direction, flying between 30 and 65 km per hour, but use different tactics. With a following wind they may fly as fast as 90 kmh. Birds navigate using visual markers, like rivers or mountains, the sun as a compass, the earth’s magnetic field and, for those that fly by night, the stars. They also fly in flocks led by experienced adults. Moths do not fly in flocks but have a genetically pre-determined preferred direction and are able to detect fast-moving winds. They only migrate on nights when the winds are favourable for the direction in which they need to travel and choose the most auspicious altitude. They may fly as far as 700 km in an eight-hour flight.
Image courtesy of Wikimedia CommonsMost of the UK’s 2,500 species of moths are resident but some are visitors, often from as far away as North Africa, some 3,000 miles. One stunning moth is the Hummingbird Hawk-moth which journeys from the Mediterranean and North Africa. It arrives between April and December with most migrants appearing in August and September. In hotter summers greater numbers are seen. This moth breeds in UK and it is thought that some of the offspring may endure in milder winters.
The Silver Y moth has been monitored flying vertically to catch faster winds at high altitude. It breeds profusely but very few moths born in Britain survive the winter.