Ireland has a newly discovered insect species, a gruesome wasp that lays its eggs inside marsh flies which are eaten from inside as the wasps grow, writes Dick Ahlstrom
A NEW INSECT species has been discovered buzzing about the marshlands at Ardkill Turlough, Co Mayo. It is a creature of nasty habits however, depositing its eggs in fly larvae that are then eaten alive by the growing young.
The new bug is a parasitic wasp of the Mesoleptus genus and has been named Mesoleptus hibernica by its discoverer, NUI Galway postdoctoral fellow, Dr Chris Williams. "It is very unusual to get something new to science, particularly a terrestrial species," says the delighted Williams.
This is the first time a parasitic species in the genus Mesoleptus and new to science has been discovered here and only three species of this genus are currently recorded for Ireland.
There are many parasitic wasp species and M hibernica is typical of most in that it lives alone rather than in a hive with others and deposits its eggs in a living host, usually the larvae or pupae of another insect species. The wasp eggs hatch out and their larvae eat their hosts from the inside out to emerge as adults, explains Williams who came to Ireland from Hengoed, mid-Glamorgan in Wales to pursue his PhD.
He is based at the applied ecology unit and the environmental change institute in Galway and made the discovery while conducting field work, looking in particular at the marsh fly (Tetanocera arrogans and T robusta).
The fly is interesting in that its larvae feed on aquatic snails, which in turn can carry liverfluke. This makes the marsh fly a potential form of biological control to inhibit the snails and therefore liverfluke transmission, Williams suggests.
The fly larvae change into pupae, living in tiny black cases called puparia that float on the water's surface. It was an encounter with these puparia that helped Williams to make his discovery. Funding for his research comes from the Environmental Protection Agency.
"I was sampling the turlough at Ardkill for fresh water snails. I collected a few puparia floating on the water and put them into a jam jar to see which species of fly would emerge. Instead of a fly a parasitic wasp emerged."
The wasps had got to the pupae or their preceding larvae first but the jam jar held two different species. He wanted to discover the species involved but unfortunately parasitic wasps are "a very difficult group to study or identify", he says.
Williams then began an international expedition to identify them, consulting first with Dr Lloyd Knutson in Italy before talking to Dr Gavin Broad at the Natural History Museum in London and finally to Drs Ilari Sääksjärvi and Reijo Jussila in Finland. They provided the final confirmation that one of the wasps was a completely new species.
"When we finally discovered that one of these insects had never been recorded before, the question then was what to call this creature.
"After resisting the temptation to name it after someone I know - who really wants to be named after a parasite - we settled on naming it Mesoleptus hibernica in honour of the country where it was discovered," Williams says.
The wasps are tiny, about four millimetres long, but now that they have emerged as a potential threat to the marsh fly, Williams is anxious to learn more about them.
The fly helps to keep the snails in check, which in turn inhibits liverfluke transmission, but if the flies become heavily predated by the wasp, this would have a negative effect on the natural liverfluke control provided by the obliging marsh fly.
He has yet to learn whether the female wasp lays her eggs in the larval stage of the fly or its subsequent pupa. These details should emerge as more is learned about this new species.