A Case of Mistaken Identity in the World of Crane Flies

From the 1800s into the 1900s, there was an unconventional scientific competition: entomologists all over the world were racing to see who could describe the most new species, which inevitably led to an unprecedented level of documentation of the world’s insect diversity.  

One group of insects that received a great deal of attention in the midst of this rivalry was the crane flies (Tipuloidea). In North America, several naturalists — such as Baron Osten Sacken, Rennie Doane, Francis Walker, E. E. Bergroth and Charles Paul Alexander — each described tens to hundreds of species in dozens of papers.  

There was a problem, however — all these naturalists had no way of rapidly and widely communicating their findings.  

In an era without Twitter, Instagram, cell phones, computers or even cameras, naturalists published their findings in scientific journals, often without photographs or drawings of the specimens they were describing. New species were presented to the world based solely off of brief paragraphs describing their appearances.  

As you can imagine, confusion ensued. 

Jon Gelhaus, PhD, curator of entomology at the Academy of Natural Sciences and professor in the Biodiversity, Earth and Environmental Science Department at Drexel University, recently identified one such instance of this kind of mix-up in his work. Another university professor working with a wastewater plant in Reno, Nevada contacted him to identify a crane fly species that was infesting the trickling filters — designed to sustain a biofilm of algae and bacteria — and interfering with the treatment of the wastewater. 

Gelhaus recognized the species as one in the large genus Dicranomyia.  He had collected the same species a number of times in western United States in natural and artificial situations where water flowed in a thin film over rocks, or in a splash zone on a rock in a stream. But Gelhaus had long puzzled what name to apply to this species as it was confused in the scientific literature.   

It had been known variously through time as Dicranomyia defuncta Osten Sacken, Dicranomyia simulans Walker or Dicranomyia concinna Williston or following the current crane fly catalog, even Dicranomyia simulans concinna Williston.  Which was correct, and did the names really refer to the same species? 

He also noted that there were actually several other similar-looking species described in the literature (for example, Dicranomyia venusta) and wondered whether they were also referring to this same species. The adults of all these forms were described as having extensively spotted wings and banded legs, unlike most other species in the genus Dicranomyia

Gelhaus reached out to Bryan Eichen, a dual undergraduate and graduate student in Drexel’s Biodiversity, Earth and Environmental Science department with co-op experience in water treatment, and together they took on a new project: to clarify who was really who among these spotted wing species in the genus Dicranomyia and, in so doing, apply the appropriate name to this pest species in sewage treatment plants.  

Who’s Who? 

Eichen and Gelhaus spent countless hours sorting specimens housed at the Academy’s Entomology Collection, along with other specimens on loan from the Smithsonian National Museum of Natural History. Through this intensive, detail-oriented work and Gelhaus’s expertise, they determined that what was once considered six separate species in the literature, were actually only three!  

“We based our determinations on differences and similarities between the pattern of veins in the wings of these flies,” Eichen says, “as well as the structure of the genitalia in male specimens.” 

Broken down, here’s what they know now: Dicranomyia venusta and D. negligens are one species; D. simulans and D. pemetica are one species; and D. defuncta and D. concinna are one species.  

But you may be wondering what will they called these single species. “The typical naming convention is that when the same species is named one or more times, the valid name is the one that was described first,” Eichen explains. As such, we are left with D. venusta Bergroth, D. simulans Walker and D. defuncta Osten Sacken.  D. venusta is a western North American species, D. simulans is primarily a species of the Boreal North and D. defuncta is found across North America.   

So which species was impacting the sewage treatment plant?  They determined that it was D. defuncta, as the natural habitat for larvae of this species — on stones within splash zones in rivers — fit well with the artificial habitat of the plant’s trickling filters where water flows in thin sheets over a corrugated surface.  

In looking through the older specimens in the museum collections and capturing the data on the specimen labels, they also found that specimens had been previously collected in sewage treatment plants at least 60 years ago, but no special publications had detailed these occurrences. 

A drawer with 154 specimens identified, labeled, and sorted by Bryan Eichen.

Why is this important? 

While sorting out the species may seem trivial, ensuring that species are properly identified is essential to the work performed by conservationists, taxonomists and museum curators. When conservationists seek to determine whether a species is at risk of extinction, they must be able to accurately survey the individuals in their habitat by using the correct identification and be able to apply the appropriate scientific knowledge in the literature to the species being observed. 

If, for instance, conservationists wanted to see whether D. venusta was endangered in a particular habitat, they may produce incorrect data if they were counting individuals of D. venusta and D. negligens separately. Similarly, many scientists look to museum collections to analyze changes in insect populations over time. They would produce an incorrect account of the history of D. venusta if they excluded specimens labeled D. negligens since both those names we now know refer to the same species. 

Eichen believes that there are probably countless examples of similar mistaken identities just waiting to be uncovered by future scientists and researchers. “And the species most likely to be improperly described are those that are regarded as uncharismatic, like crane flies,” he says. 

Since there is not a constant push for new research on smaller, less flashy species like insects, their improper identifications can go unnoticed for long periods of time. Eichen hopes that his research will inspire others to take a second look at their specimens, because they just might not be who they seem! 

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