Microgastrinae

Death from below: the first video of a parasitic wasp attacking caterpillar underwater

Named after fictional monster Godzilla, a parasitic wasp becomes the first observed and filmed to dive underwater for several seconds, in order to attack and pull out caterpillar hosts, so that it can lay its eggs inside them before releasing them back in the water.

A very few species of parasitoid wasps can be considered aquatic. Less than 0.1% of the species we know today have been found to enter the water, while searching for potential hosts or living as endoparasitoids inside of aquatic hosts during their larval stage.

Within the subfamily Microgastrinae (family Braconidae), only two species have previously been recorded to be aquatic, based on their parasitism of aquatic caterpillars of moths. However, none has been known to actually dive in the water.

Recently, during their research work in Japan, Dr. Jose Fernandez-Triana of the Canadian National Collection of Insects and his team found and recorded on camera the first microgastrine parasitoid wasp that dives underwater for several seconds, in order to attack and pull out caterpillar hosts, so that it can lay its eggs inside them before releasing them back in the water.

Interestingly, the wasp, which was described as a new to science species in the open-access, peer-reviewed scientific Journal of Hymenoptera Research, was given the awe-striking name Microgaster godzilla, because its emergence out of the water reminded the scientists of the Japanese iconic fictional monster Godzilla.

In the video, the female wasp can be seen walking over floating plants as it searches for hosts, specifically larvae of the moth species Elophila turbata, which constructs a portable case from fragments of aquatic plants and lives inside it near the water surface. Once the wasp finds one of those cases, it first probes it repeatedly with its antennae, while moving around. Eventually, it forces the larvae to come out of the case and parasitizes it by quickly inserting its ovipositor. In some cases, the wasp has to submerge completely underwater for several seconds, in order to find and pull the caterpillar out of its case. To do this, the species has evolved enlarged and strongly curved tarsal claws, which are thought to be used to grip the substrate as it enters the water and looks for hosts.

A female wasp Microgaster godzilla seeks out a moth caterpillar, dives in the water and pulls it out of its case, in order to parasitize it by quickly inserting its ovipositor.
Video by Dr. Jose Fernandez-Triana

As for the curious choice of name for the new species, Dr. Jose Fernandez-Triana explains:

“The reasons why we decided to use the name of Godzilla for the wasp species are interesting. First, being a Japanese species, it respectfully honours Godzilla (Japanese: ゴジラ, Hepburn: Gōjira), a fictional monster (kaiju) that became an icon after the 1954 Japanese film of the same name and many remakes afterwards. It has become one of the most recognizable symbols of Japanese popular culture worldwide. Second, the wasp’s parasitization behaviour bears some loose resemblance to the kaiju character, in the sense that the wasp suddenly emerges from the water to parasitize the host, similar to how Godzilla suddenly emerges from the water in the movies. Third, Godzilla has sometimes been associated, albeit in different ways, with Mothra (Japanese: モスラ, Hepburn: Mosura), another kaiju that is typically portrayed as a larva (caterpillar) or an adult moth. As you can see, we had biological, behavioural and cultural reasons to justify our choice of a name. Of course, that and having a bit of fun, because that is also an important part of life and science!”

Beyond unusual behaviours and funny names, Dr. Fernandez-Triana wants to emphasize the importance of multidisciplinary work and collaboration. The team that published this paper got to know each other at an international meeting devoted to biological control (The 5th International Entomophagous Insects Conference in Kyoto, Japan, 2017).

“I was very impressed by several presentations by Japanese grad students, which included video recordings of parasitoid wasp biology. As a taxonomist, I am always impressed with the quality of research done by colleagues in other fields. In this case, we saw an opportunity to combine our efforts to study the wasp in detail and, when we found that it was a new species, we described it together, including adding the filmed behaviour to the original description. Usually, taxonomic descriptions of parasitoid wasps are based on dead specimens, with very few details–often none–on its biology. Thanks to my biocontrol colleagues, we could add more information to what is known about the new species being described. Hopefully we can continue this collaboration and combined approach for future studies”.

Original source:

Fernandez-Triana J, Kamino T, Maeto K, Yoshiyasu Y, Hirai N (2020) Microgaster godzilla (Hymenoptera, Braconidae, Microgastrinae), an unusual new species from Japan which dives underwater to parasitize its caterpillar host (Lepidoptera, Crambidae, Acentropinae). Journal of Hymenoptera Research 79: 15-26. https://doi.org/10.3897/jhr.79.56162

All microgastrinae wasps from around the world finally together in a 1,089-page monograph

With 3,000 known species and thousands more left to describe, the wasps of the subfamily Microgastrinae are the single most important group of parasitoids attacking the larvae of butterflies and moths, many of which are economically important pests. Consequently, these wasps have a significant impact on both the world’s economy and biodiversity.

Due to their affinities, these wasps are widely used in biological control programs to manage agricultural and forestry pests around the globe. Further, they have also been prominently featured in many basic and applied scientific research (e.g. chemical ecology, biodiversity studies, conservation biology, genomics, behavioural ecology). However, the information about Microgastrinae species is scattered across hundreds of papers, some of which are difficult to find. To make matters worse, there has never been an authoritative checklist of the group at a planetary scale.

All currently available information about the group is now brought together in a large monograph of 1,089 pages, published in the open-access, peer-reviewed journal ZooKeys. The publication presents a total of 2,999 valid extant species belonging to 82 genera. On top of that, the monograph features fossil species and genera, unavailable names and the institutions that store the primary types of all listed species.

Moreover, the researchers have included extensive colour illustrations of all genera and many species (thousands of images in 250 image plates); brief characterisation and diagnosis of all genera; detailed species distributions (within biogeographical regions and per individual country); synopsis of what is known on host-parasitoid associations; summary of available DNA barcodes; estimations of the group diversity at world and regional levels; as well as notes on individual species upon request.

“Compiling this annotated checklist was, more than anything, a labour of love,”
says Dr. Jose Fernandez-Triana of the Canadian National Collection of Insects, lead author of the paper.

Monograph paper openly published in *ZooKeys* at
https://doi.org/10.3897/zookeys.920.39128

“For the past six or seven years, we have spent thousands of hours pouring through hundreds of publications, reading original descriptions in old manuscripts, checking type specimens in many collections worldwide, exchanging information with colleagues from all continents. For the past year or so, I basically stopped all other ongoing research projects I was involved with, to focus solely (almost obsessively!) on finishing this manuscript. The work was often tedious and mind-numbing, and many times I had the temptation to delay the completion of the paper for a later time. However, I was lucky that the other co-authors were just as passionate as myself, and we all pushed each other to finish the task when energy ran low.”

Fifteen species of microgastrinae wasps showing the incredible diversity within the subfamily. Note the variety of colours and shapes.
Image by Dr. Jose Fernandez-Triana

“For the past few years, the Microgastrinae wasps have been one of the most intensively studied groups of insects, at least from a taxonomic perspective,” he adds. “Just to give you an idea: between 2014 and 2019 a total of 720 new species of Microgastrinae were described worldwide. That is an average of one new species every three days, sustained over a six-year period and showing no signs of slowing down.”

He also points out that many scientists from many different countries and biogeographical regions have been involved in the description of the new species. The paper recognises them all and their contributions in the Acknowledgements section.

“You could even say that we are witnessing a renaissance in the study of this group of wasps. However, even then, what has been done is only the tip of the iceberg, as we estimated that only 5 to 10% of all Microgastrinae species have been described. That means that we do not have a name, let alone detailed knowledge, for 90-95% of the remaining species out there. Perhaps, there could be up to 50,000 Microgastrinae wasp species worldwide. It is truly humbling when you consider the magnitude of the work that lies ahead.”

Yet, it is not only a matter of counting huge numbers of species. More importantly, many of those species either have already been put in use as biocontrol agents against a wide range of agricultural and forestry pests, or have the potential to be in the future.

For applied scientists, working with hyperdiverse and poorly known groups such as Microgastrinae is even more perplexing. Navigating the maze of old names, synonyms (species described more than one time under different names), homonyms (same names applied to different species), or unavailable names (names that do not conform to the rules of the International Commission of Zoological Nomenclature) is a daunting task. Often, that results in the same species being referred to in several different ways by different authors and academic works. Consequently, many historical references are full of misleading or even plainly wrong information. Meanwhile, it is very difficult to seek out the useful and correct information.

The present annotated checklist could work as a basic reference for anyone working with or interested in the parasitoid wasps of the subfamily Microgastrinae. In the future, the authors hope to produce revised editions, thus continuing to incorporate new information as it is generated, and to also correct possible mistakes.

“We welcome all kinds of criticisms and suggestions. And we hope that biocontrol practitioners will also help us, the taxonomists, to improve future versions of this work. However, for the time being, let me say that it is a tremendous relief to get this first version out!”
concludes Dr. Fernandez-Triana.

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Original source:

Fernandez-Triana J, Shaw MR, Boudreault C, Beaudin M, Broad GR (2020) Annotated and illustrated world checklist of Microgastrinae parasitoid wasps (Hymenoptera, Braconidae). ZooKeys 920: 1-1089. https://doi.org/10.3897/zookeys.920.39128.

Ottawa confirmed as the biodiversity hotspot for a subfamily of wasps in North America

What usually comes to mind when speaking about biodiversity hotspots are tropical regions, pristine areas and magnificent forests. Meanwhile, it is quite rare that a city in a temperate zone is considered significant in terms of biodiversity, much less mentioned as a hotspot. Yet, the city of Ottawa together with its surroundings, despite having population surpassing 1 million people, is now confirmed to be the locality in North America with the most recorded species of braconid wasps in the subfamily Microgastrinae, a group of parasitic insects that attack caterpillars and play an important role in the natural biocontrol of agriculture and forestry pests.

A study published in ZooKeys reports 158 species within 21 different genera of Microgastrinae for Ottawa. “To put this into perspective,” says Dr. Jose Fernandez-Triana, affiliated with the Canadian National Collection of Insects and lead author of the paper, “if Ottawa (a relatively small area of less than 7,800 km2) would be considered as a country itself, its species total would rank 17th among all countries in the world.”

There are close to 200 species of microgastrine wasps known from Canada and around 350 – from North America. Thus, the fauna in Ottawa equals to three quarters of the total recorded for the entire country, and almost half of all species in the Nearctic region. In fact, the diversity in the Canadian capital represents by far the highest number of species ever recorded for a locality in North America, a consequence of the city being a transition from an eastern deciduous forest biome to a boreal biome, with small areas of unusual habitats like dunes, alvars, floodplains and bogs.

Based on the analysis of almost 2,000 specimens, collected between 1894 and 2010, and housed in the Canadian National Collection of Insects, the paper also reports two new species for North America and two additional species records for Canada and Ontario, as well as dozens of new additions to the regional fauna. Seasonal distribution showed several peaks of activity, in spring, summer, and early fall.

The study highlights the incredible diversity of parasitoid wasps and how much remains to be discovered, even in temperate areas and/or city environments. “It is possible that southern localities in North America are eventually found to be more diverse than Ottawa,” notes Dr. Fernandez-Triana. “But for that to happen one would need to find an area that has a variety of habitats and has also been thoroughly sampled over the years, with thousands of specimens available for study.”

“In the meantime,” jokes the scientist, “the citizens of the Canadian capital will have the bragging rights in North America, at least for microgastrine wasp diversity.”

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Original source:

Fernandez-Triana J, Boudreault C, Buffam J, Mclean R (2016) A biodiversity hotspot for Microgastrinae (Hymenoptera, Braconidae) in North America: annotated species checklist for Ottawa, Canada. ZooKeys 633: 1-93. https://doi.org/10.3897/zookeys.633.10480