Researchers from the University of California, Riverside rediscover the wasp species Oobius depressus, which was last seen in 1914.  The female Oobius depressus grows up to 1.2 millimeters long, sporting a black, flattened body.

The Oobius depressus is the natural enemy of the locust borer or wood-boring beetle, a beetle species considered as pest by many. The wasp actually parasitizes the beetle’s eggs.

Researchers say that rediscovering the wasp is very significant. Locust borers are a pest because they kill the black locust trees that helped build the historical Jamestown, where colonists first settled in the US.

wasp species

The rediscovered wasp species can help control the beetle population that deteriorated this broomstick.Credit: Túrelio/Wikimedia

The Oobius depressus wasp was last seen alive more than 100 years ago. There were specimens of the species collected and preserved but these were missing heads and antennae.

Therefore, Serguei Triapitsyn, an entomologist and the director of the university’s UC Riverside Entomology Research Museum, sought to find better wasp specimens. The search was complicated, however.

Finding an adult locust borer is easy since they can be found in the Midwest during early autumn. Meanwhile, its eggs are not that easy to locate.

So the research team equipped a black locust located in Rose Lake State Wildlife Area, Michigan with an insect trap. This allowed the collection of beetles and other insects that live on the tree. The task started from August 2015 up to October of the same year.

The trap was composed of ethanol. This chemical can also keep the specimens preserved for a longer period of time.

The insects collected in ethanol were then sent to the UC Riverside Entomology Research Museum earlier this year. The research team found that one female wasp was actually an Oobius depressus.

The rediscovered wasp species was then photographed and re-described. These results will be published in the journal The Great Lakes Entomologist by the Michigan Entomological Society.