Ormyrus’s tiny iridescent bot has long looked suspicious to a parasitic wasp. It wasn’t the amazing beauty of the hornets – wasps can be traditionally attractive too – but their strategy in life. Parasitic wasps lay their eggs on or inside insects and other arthropods, and the larvae eat their way out when they hatch. Each type of parasitic wasp tends to favor one host or several families. But Ormyrus labotus has been observed laying eggs in more than 65 different species of insects — more than one or a few.
Ormyrus labotus parasitizes gall wasps, which lay their eggs on plants and stimulate them to form protective, swollen structures called rounds around the larvae (a parasite, in a parasite!). When balls are formed from different types of wasps, they take on a variety of sizes and shapes. Some are tougher than others, and some have unusual defensive strategies. There are beams covered with chambers, secreting nectar or bristle with fibers. Parasitic wasps often have specialized adaptations that allow them to shed certain types of gall.
But Ormyrus labotus seemed to have had no problem penetrating an assortment of balls: round, lime-green balls and prickly yellow moths on the leaf blade and stubborn lumps on a twig. “It seemed strange that a species could effectively attack all these different orcs,” said Sophia Sheikh, a doctoral student at the University of Chicago who researched wasps when she was at the University of Iowa.
It turns out that entomologists have good reasons to be skeptical. After extracting DNA samples from parasitic wasps collected from oak trees across the country, Sheikh and colleagues at the University of Iowa revealed that Ormyrus labotus is actually a complex of at least 16 genetically different species that are indistinguishable by eye. Their research was published Wednesday in the journal Insect Systematics and Diversity.
The researchers note that the research paper is the latest in a series of studies revealing types of parasitic insects put forward as aggregators for many species. And scientists are sure that more of this hidden diversity lurks in insects that have not been studied for decades — there may be more Ormyrus labotus species out there.
These examples teach scientists to “suspect” what kind of parasitic wasps are thought to be generic, said Josephine Rodriguez, an entomologist at the University of Virginia in Wise, who was not involved in the research.
Andrew Forbes, an evolutionary biologist at the University of Iowa, said the paper came out of a larger project studying the coevolution of North American gall wasps and their parasites. “Nobody has looked at these groups for 50 to 100 years,” said Miles Zhang, a research entomologist at the USDA Systematic Entomology Laboratory, adding that much of the work on spinner wasps has been completed by biologist Alfred Kinsey, best known with it. The Human Sexual Activity Scale of the same name.
Sheik and Anna Ward, a graduate student in Iowa, spent several years uprooting the sprite from oak trees, which included searching for iNaturalist, a social network of biologists and other scientists, and inviting themselves into people’s backyards. They brought the goblins to the lab, put them in separate cups in an incubator the size of a refrigerator, and waited to see if the gall wasps hatched, parasitic wasps, or both—two wasps with one stone. “It’s often like 20 wasps with one stone,” Forbes explained. “Each gall wasp is attacked by 10 to 25 different types of parasites.”
While the wasps hatched and chewed the exit holes of the mites, the researchers extracted samples of the insects’ DNA to check for genetic variation among them. They then compared the genetic findings with the environmental findings, meaning the wasps that were found on tannins and tree species. They also studied the anatomy of insects, which was less useful because wasps looked very similar. This was how they found that wasps most likely represented at least 16 species. (There were likely two more, but the researchers didn’t have enough samples to be sure.)
While the researchers speculated that Ormyrus labotus was not a single species, the 16 to 18 distinct species came as a surprise. “Those are all of these in our little specimens,” Sheikh said. “That means there’s a lot we haven’t picked up yet.”
The paper does not formally describe or give a name to any species in the complex, as such taxonomic work would require further evidence and microscopic measurements of wasps’ body parts. The DNA analysis examined one mitochondrial bar-coding gene. But Forbes hopes that someone will take up the mantle of classification and name each of these 16 to 18 long-overlooked wasps. “This research adds to the situation that we need more support to train and fund more taxonomic experts,” Rodriguez said.
Distinguishing dozens of similar-looking slash wasps of a single species is not just a taxonomic exercise. The extreme specialties of parasitic wasps make them excellent pest managers; In Hawaii, the parasitic wasp Eurytoma erythrinae drastically reduced populations of the gall wasp that was threatening the native Willowley tree.
In Zhang’s view, entomologists often focus on bees and ants – the most dazzling insects in the order Hymenoptera – while neglecting tiny parasitic wasps.
“It’s underestimated because it’s so small,” Zhang said. “But they are iridescent, with beautiful bright eyes.”
Chang, who works at the Smithsonian’s National Museum of Natural History, says the museum contains at least 100 specimens named after Ormyrus labotus. Small wasps are usually stored in drawers. But if brought into the light, their iridescent bodies would shimmer, looking different from every angle.