The species this week is the non-native micro moth Tachystola acroxantha. Its homeland is Australia, but it is now introduced to the UK, the rest of Europe, and New Zealand, probably as larvae, eggs or cocoons in plant pots. Its first British record was from Devon in 1908, and the species remained South-Western until the 1990’s, when it began to rapidly expand its range. It is now found throughout Southern coastal counties, in Southern Wales, East Anglia and North to Lancashire. This range expansion is almost certainly associated with climate change, bringing our own climate slightly closer to that in Australia. T. acroxantha is commonest in the South-west, London and Bristol areas. See the distribution map here:
The impact of the invasive T. acroxantha on native species is relatively unknown, but I think it is unlikely to be very significant. The larvae feed on dry leaf litter, in a loose silken tube, so are unlikely to compete with very many other species. Also, despite expanding its range very quickly, T. acroxantha never seems to be very abundant where it occurs. So far, from two nights of moth trapping at the Penryn campus (in Cornwall, where T.acroxantha is frequent), I’ve seen one individual. I’ve also found a single, fairly fresh adult whilst beating Oak, pictured below:
That brings me nicely on to identification. When fresh, this species is unmistakable. The moth is 7-10 mm in length, and the unusual overall shape and bright yellow patches along the termen (which is incurved, adding to the odd shape) are diagnostic. Problems with identification only occur in very faded specimens, where the ground colour may fade from red-brown to grey, and the yellow may be worn off. In these instances, confusion with other members of the family, such as the ubiquitous Brown House Moth (Hofmannophila pseudospretella) is possible. Unless the wings are very damaged, the shape of the moth is usually still distinctive.
Tachystola acroxantha is best found by moth trapping in garden or parkland areas where it is most abundant (the South-west, London etc.). It probably has multiple broods through the year, as it can be caught from April right through to December. I have no experience in finding the larvae, but sifting through leaf litter in suitable situations would probably be a good place to start.
In conclusion then, this attractive little moth seems to fit in with our native Lepidopteran fauna quite harmoniously, so I won’t be complaining when it turns up back at home in Huntingdonshire! My prediction is August 2018.