Parasitica is a huge group of Hymenopterans, outnumbering all vertebrates known globally in the number of species. They differ from their close relatives, stinging wasps, in having an ovipositor rather than a stinger. Ichneumonid larvae parasitize other insects. Since the hosts are often tree pests, e.g., capricorn beetles, or crop pests, some ichneumonid wasp species are used for biological control. To humans, however, such wasps are not a threat.
Megarhyssa rixator Schellenberg, 1802 wasps parasitize horntail larvae during egg-laying.
Vodlozersky National Park. Photo: A.E. Humala / FRI KarRC RAS
One of the world's most reputable experts on Ichneumonid wasps is Andrei Humala, Leading Researcher at the Laboratory of Landscape Ecology and Forest Ecosystem Protection at the Forest Research Institute (FRI KarRC RAS). A graduate of the Leningrad State University and the postgraduate program at the Zoological Institute RAS, he has been studying ichneumon wasps – one of the largest and yet least studied families of insects – for over thirty years.
– Ichneumonids is a difficult word for people without a specialized educational background, even if they speak a foreign language. Several years ago, an international group of experts proposed a new name for members of the family Ichneumonidae – Darwin wasps – one of the goals for the suggested change being wider awareness of these wasps, – explained the scientist.
Andrei Humala deploying a Malaise (tent) trap in the Lapland Nature Reserve (Murmansk Region).
Once inside the "tent," insects gather in the upper corner in the attempt to escape through a special opening, but eventually find themselves in a jar filled with alcohol. Photo courtesy of Andrei Humala.
The primary geographical focus of the research conducted by entomologists at the KarRC RAS is Karelia and other regions of Northwestern Russia. Yet, being a renowned expert on Ichneumonid wasps, Andrei Humala is also frequently invited to participate in international studies.
For instance, during a working visit to the Zoological Institute RAS, the Karelian researcher examined insect collections brought over by Russian entomologists from expeditions to African countries and discovered an Ichneumonid genus never previously described for this continent. After this finding was published, he was contacted by South African entomologist Simon van Noort, who curates the insect collection at the Iziko Museums of South Africa in Cape Town, with a proposal for collaboration. Van Noort provided high-resolution images of several specimens. The collaboration has resulted in the discovery of four new Darwin wasp species: Eusterinx dzanga Humala & van Noort, E. kirkwoodi Humala & van Noort, E. gamka van Noort & Humala, and E. kibale van Noort & Humala. They are now all included in the illustrated guide to known Afrotropical species of Eusterinx, available online.
A female Eusterinx gamka – a new species described as a result of examining specimens from the museum in Cape Town.
Photos: Journal of Hymenoptera Research 98
Examining unsorted material from previous years on one of his trips to the Zoological Institute, the entomologist noted an unusual ichneumonid specimen originating from Primorsky Krai: “I noticed immediately the body punctures were very different from what I saw in any other species of this genus before”. As a result, a new species was described and pictured, and given the name Microleptes scabrum. In an article published in Far Eastern Entomologist, the scientist compares it against known congeners, remarking on an unusually coarsely sculptured body.
The entomologist managed to quickly recognize the new species due to his previous experience from joint research with scientists from South Asia.
– Just a year earlier, we published an article with colleagues from India and Thailand, whose insect fauna is also yet poorly studied. They sent a series of high-resolution photographs taken with professional equipment for me to analyze, – noted Andrei Humala.
During this work, scientists reported, for the first time ever, on parasitic wasps of the subfamily Microleptinae for India and Thailand. In total, five new species were discovered. They also found the Chinese species M. xinbinensis Sheng & Sun, previously not encountered in India. The results of this study were published in the international Journal of Hymenoptera Research. The article provides an identification key to known species of Microleptes – a rare and poorly studied subfamily, which had only been composed of 14 species prior to this study.
Modern remote work technologies help the Karelian scientist efficiently overcome geographical barriers, but this has largely become possible due to the experience he has accumulated over the years of scientific travel. The specialist has been invited quite a few times to work with entomological collections in museums across Europe and in South Korea. For instance, an outcome of joint processing of samples with colleagues in Germany was a checklist of German parasitic wasp species. In Norway, the entomologist also set traps, collected and analyzed the samples within a project (2011-2012). Twice, in 2010 and 2016, the scientist had the opportunity to work in Mexico.
Andrei Humala on an expedition in Tamaulipas, Mexico. Photo courtesy of A. Humala
– What makes the Mexican parasitic wasps of the group I study especially intriguing is that they had not been investigated at all before. In Europe, insects have been described for hundreds of years already, and by specialists of varying qualifications. Besides, the type specimens are now housed across different museums and countries, so pooling it all together is very challenging. But when you start from scratch, it's a sheer pleasure. In Mexico, of course, the parasitic wasp species are mostly different from those in the Palearctic region. They look brighter, – the entomologist clarified.
The scientist’s activities in Central America have resulted in descriptions of over fifty new parasitoid wasp species. This material was published in several articles and the monograph «Mexican species of the genus Orthocentrus (Hymenoptera, Ichneumonidae: Orthocentrinae)», and publication of scientific articles continues.
Parasitic wasps, part of the entomology collection of the Laboratory for Landscape Ecology and Forest Ecosystem Protection, Forest Research Institute KarRC RAS. Photo: M. Dmitrieva / KarRC RAS
Throughout his scientific career, Andrei Humala has discovered and described 3 genera and 149 species of parasitic wasps. As the scientist himself admits, there are still many unprocessed materials and even more plans, so these are most certainly just interim results. In the upcoming season, entomologists will continue their study of insects in the Zavidovo National Park, which they started last year. As always, the focus remains on Karelia, where there is also a chance of new discoveries.
– Darwin wasps are an incredibly diverse group of ichneumonids. Some of them are very narrow specialists. For example, there are parasitic wasps that would even go underwater to infect caddisfly larvae. They create an air tube from their accessory glands, allowing the larva to breathe underwater. They are quite numerous in China, but only one such species is known for Europe, and it’s very rare. I found one specimen in samples from the Vologda Region, and it has also been reported for Finland. It may also occur Karelia, but we haven’t encountered it yet, – shared Andrei Humala.