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2 Posts tagged with the parasitoid_wasps tag

Two species of wasp have been identified as belonging to a whole new genus endemic to the isolated Atlantic island of St Helena.


St Helena, a British Overseas Territory, is home to more than 400 species that can't be found anywhere else. However, the wildlife is under serious threat from development and invasive species.

Napoleon complex

The new wasp genus, named Helenanomalon in honour of its home territory, belongs to a family of parasitoid wasps - those that spend a part of their lifecycle on another organism that they eventually kill. However, little is known about the specific lifestyle of Helenanomalon since only a handful of specimens are known to exist.


One of the new wasps species, Helenanomalon bonapartei


The most recent specimens came to the Museum following a collecting expedition in 2006 that included the former Head of Entomology collections at the Museum, Howard Mendel. On re-examining the specimens, and a couple of others at the Musée de l'Afrique Centrale, Museum hymenoptera curator Dr Gavin Broad assigned them to two different species in the new genus:

These little wasps belong to the family Ichneumonidae, a huge family with over 24,000 described species in the world, but with only six species known to have made it all the way to St Helena. That two of these species form a genus not known anywhere else in the world is remarkable.

One of the new species, Helenanomalon bonapartei, is named after St Helena's most famous exile, whilst Helenanomalon ashmolei is named after Philip and Myrtle Ashmole, who have led recent work in exploring and documenting the fauna of St Helena.

Lost giants

Islands like St Helena often host unique organisms that have evolved in isolation for millions of years. However, these species are also extremely vulnerable to changes such as introduced predators and habitat loss.


St Helena used to be home to the world's largest earwig, the giant earwig, which reached over 8cm long and lived in deep burrows. Only a few specimens of the giant earwig have been recorded, and several scouting trips since the 1960s have failed to find any living examples. It is now considered extinct.


St Helena giant earwig, Labidura herculeana


Says Dr Broad:

The extinction of the giant earwig was a sad reminder of how vulnerable island endemics can be. There is still much work to be done on assessing just how unique the St Helena fauna is, and Philip Ashmole tells me that they have collected other potentially new genera of insects and spiders but the taxonomy of the groups concerned is difficult and there are few people with the expertise.


The native vegetation has been massively reduced by the usual pressures of introduced goats, non-native species, inappropriate agriculture, and so on. Restoring the native vegetation, particularly the seriously denuded forests, is the most important step in conserving the unique invertebrates.


Sub-millimetre-sized wasp discovered in scientist's son's playground.


Museum wasp expert Dr Andrew Polaszek has identified a new species of tiny wasp living inside whiteflies on a tree in his son's playground in Sevenoaks, Kent.


The wasp is a parasitoid. While true parasites depend on other organisms their whole lives, parasitoids just lay their eggs in other organisms. The larvae of newly discovered wasp, named Encarsia harrisoni, are born inside whiteflies and eat their way out.


It was the whiteflies on a maple tree in the playground that alerted Dr Polaszek to the presence of the wasp:


'I noticed some of the whiteflies looked slightly different to the others so I took them to the laboratory. When I saw the wasp inside I knew it looked different to anything I'd seen before.'




Not a tourist


Dr Polaszek made the discovery five years ago, but there was a lot of work to do to define it as a new species. Even more surprising to Dr Polaszek is that the new species is native to the UK.


'I thought it might be a species from Northern Europe that had come over to the UK. I was really surprised when I realised it was native to the UK and was previously unknown. Finding an undiscovered insect in the rainforests of Borneo is relatively easy but the fauna of England is some of the most studied in the world so to find something new here is a real thrill, and makes it even closer to my heart.'


In those five years Dr Polaszek has been regularly collecting the new wasp, but has never found a male, suggesting that females can lay eggs without them. This is similar to other parasitoid wasps, such as the related Encarsia formosa.


What's in a name


The new species is named after local scientist Dr David Harrison, chairman of the Harrison Institute that promotes taxonomic research to support biodiversity studies and conservation. The institute is only a few hundred yards from the trees where Encarsia harrisoni was discovered.


Dr Harrison has a few species named after him, but finds the new wasp especially intriguing:


'I now have a flea, a bug, a sand cat and a wasp named after me, which is obviously quite an honour. Dr Polaszek's wasp is a particularly interesting one - it was found right here in Sevenoaks just a few hundred yards from my home.'