Two New Parasitoid Wasps That Eat Their Hosts From The Inside Out Discovered In Ugandan Jungle

E. quagga, a new species with zebra-like markings. Hopkins et al./ZooKeys 2019; CC BY 4.0

Deep in the jungle of Uganda’s Kibale National Park, scientists have been collecting hundreds of parasitoid wasps – critters that lay their eggs in the bodies of unsuspecting insects, before the larvae eat their way out – greatly improving our knowledge of some poorly understood species. Among them, the researchers discovered two species new to science: Epirhyssa quagga, a stripy creature named after the zebra (Equus quagga), and Epirhyssa johanna.

Parasitoid wasps are famous for being particularly nasty little beasties. They differ from conventional parasites in that they eventually kill their hosts – their larvae live inside insects and arachnids, eating away at them from the inside out. But they don’t stop there, some types turn spiders or cockroaches into their zombie slaves, with one species transforming innocent ladybirds into their own personal zombified bodyguards. Be glad you’re not a bug.

The group of wasps that the two new species belong to are rhyssines, which have some gruesome parasitic tendencies. They parasitize wasp and beetle babies, or larvae, that live in decaying wood. The rhyssine larvae feast on their host’s innards as it lays motionless, paralyzed by the mother wasp when she laid her eggs. Female rhyssines have impressively long ovipositors (egg-laying organs) attached to their tails.

Specimens of rhyssines have been lacking, so we still have a lot to learn about them. During their fieldwork, the researchers managed to collect 448 wasps in big, tent-like traps and captured another eight in handheld nets. In total, these comprised six different species, including the two new ones. The discoveries bring the total number of Afrotropical species up to 13.

E. johanna up close. Hopkins et al./ZooKeys 2019; CC BY 4.0

"A good example of how poorly tropical rhyssines are known is the species Epirhyssa overlaeti, which is the largest African rhyssine,” said project leader Tapani Hopkins of the University of Turku in Finland. “Only two females were known before, one collected in the 1930s in the Congo and the other one in Cameroon in the 1980s. Now, at one single Ugandan site, we found large numbers of both females and males. This completely changed what is known of the distribution of the species."

Rhyssinae is a subfamily of wasps that includes 259 species distributed around the world. The largest rhyssines can grow to over 10 centimeters (4 inches) in length, which we can all agree is uncomfortably big for a wasp. However, the tropical African species are a little smaller, with E. overlaeti, the largest, measuring up to 37.8 millimeters (1.5 inches).

E. johanna has a unique color pattern and measures 8.4 millimeters (0.3 inches) in length. It is named after Hopkins’ wife, Johanna, as it “is known from only one, quite exceptional, female specimen.” In contrast, E. quagga is known from 46 specimens and can grow up to 14.3 millimeters (0.6 inches) in length. The insects are described in the journal ZooKeys.

The researchers note that rhyssines are probably much more common in tropical Africa than we thought and say it’s still too soon to conclude how the species richness of these insects is distributed around the planet. It seems likely there are still many parasitoid wasps waiting to be uncovered.

E. quagga. Hopkins et al./ZooKeys 2019; CC BY 4.0

 

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