Mystery alien of unknown origin is spreading
THE appearance of harvestmen is one of the signs that heralds the arrival of autumn. Since they have eight legs these life forms are more closely related to spiders than to six-legged insects. However, unlike spiders they don’t have fangs or poisonous venom to kill their prey, so harvestmen comprise a small but distinct group of their own.
Harvestmen are completely harmless to humans. They start to appear resting on walls in late summer and they are so called because their peak abundance coincides with harvest time in the farmers’ annual calendar.
They are in the news at present because the latest alien to colonise Ireland is a harvestman. For the time being, the alien of unknown origin is known as ‘ Leiobunum species A’.
Leiobunum species A was first discovered in the Netherlands in 2004. Since then, it has been recorded in Germany, Austria, Switzerland, Poland, and the UK in 2009. There is a report of the species being recorded in Dublin in 2021 and recently naturalist Brian Murray discovered the species breeding at the Curragh Camp in Co Kildare. The rate at which the alien is spreading has been described as “alarming”.
The species is typically found around houses, outside buildings, on walls, under window sills, and gutters. Adults are easy to identify due to two unique characteristics: they have a huge leg span of 15cm or six inches, far in excess of any of our native species, and they form impressive social aggregations of fifty to several hundred individuals.
Long-legged harvestmen should not be confused with the Daddy Long Legs that is a fly with wings, or the gangly Cellar Spider that is common in many buildings. September is the peak time for seeing harvestmen. They appear to live for one year only. As winter establishes a grip it is assumed that adults die, and that the species overwinters in the form of eggs.
The National Biodiversity Data Centre asks members of the public to keep an eye out for the remarkable alien harvestman and to report sightings to assist scientists track the distribution of the mystery arrival. Sightings should be reported via https:// records.biodiversityireland.ie/record/invasives#7/53.455/-8.016 together with the best images possible.