Migrant Moths

 

The term 'migrant moths' refers to individuals who have made their way to the UK from another country. The picture is clouded by migrant species that have temporarily colonised or are in the process of full colonisation. Then there are resident species of which numbers are boosted by migration. Added to this is the accidental introduction of moths by importation in food or plant material, which are known as adventives. Deliberate introductions, legal or not, can occur but are more frequently associated with butterflies. Sometimes an open mind is required in judging which of these situations is which.

 Convolvulus Hawkmoth

  

I think it's fair to begin with a word of warning concerning the study of migrant moths. The subject can become addictive, which has been known to affect decisions such as holiday destinations and even, in extreme cases, living locations. However, its draw does mean that you won't be alone in the study, which leads to good sources of up-to-date information on the subject.

One such source is Atropos. This journal is produced three times a year and available on subscription. It is concerned with the migration of moths, butterflies and dragonflies into the UK. The Atropos website has a Flight Arrivals section where you can see recent arrivals and add your own. There's also a section that shows an updated list of migrants with the number of UK records for each species.

For Facebook users, Migrant Lepidoptera (GB and Ireland) is recommended (private group, 2.2k members). Posts usually contain photographs of the species seen with their locations. The administrators often post upcoming weather charts, which can be a good indicator of possible migration events throughout the year and give the chance to put traps out in good time. These events are often accompanied by falls of Saharan dust into the UK.

For our region, there's a Migrants option in the Arrivals menu of the West Midlands Moth Atlas (available only to Golden Cinnabar members). This contains annual migrant information from 2020 onwards and includes migrant records, recorders and their locations. The page does not include the common migrants Silver Y, Rush Veneer and Diamond-back. That reminds me of a time when I was growing Dwarf Beans commercially: the field was struggling to compete with self-set oilseed rape until thousands of Diamond-back larvae began eating the brassica.

 

Regionally, most of our migrant sightings occur in late summer, although they can occur at any time given the right conditions (including larval records). With our warming climate, more years are now suitable for migrants and new species are often recorded. Planting night-scented flowers in the garden can help attract species, such as the spectacular Convolvulus Hawk-moth being drawn to Nicotiana flowers; Hummingbird Hawk-moth is a regular migrant that's attracted to a variety of flowering garden plants. Some species will come to pheromone lures and light, including Dewick’s Plusia which is attracted to the Ni lure. Sugaring and torching (inspecting ivy blooms and old fruit after dark) can also be productive for migrants, especially later in the year. With close attention to your moths, it's still perfectly possible to add records of new migrant species to your county list – with your name attached!