A new species of assassin bug was discovered by accident, when scientists were working on the nymphs of three known species.
Dr. J. E. McPherson, professor emeritus at Southern Illinois University, was working with colleagues on a key to the nymphs of three midwestern species of assassin bug in the genus Sinea (i.e., S. complexa, S. diadema, and S. spinipes) in 2006 and to test their key for accuracy, they asked several others to check it by comparing it with insects in their collections or laboratories.
However, Dr. Scott Bundy from New Mexico State University, who found discrepancies in specimens that had been collected in New Mexico and identified as S. complexa.
Bundy said that when his bugs would not key out properly, he assumed there was just an error in the key and he then sent some western specimens and it was found that the two are different.
Since its original description, scientists had believed S. complexa and S. incognita to be a single species that was found from California to Missouri and Illinois. This long-time hidden identity is responsible for the new bug's specific epithet.
The two species also are separated by geography as Sinea complexa occurs in the western and southwestern United States south into Mexico, whereas Sinea incognita occurs from Maryland south to Georgia and west to Kansas and Texas.
The new species, Sinea incognita, is described in the Annals of the Entomological Society of America in an article that also explains the differences between it and its close relatives, the aforementioned S. complexa and another called S. integra, which is found from Arizona and Texas south through Mexico to, at least, Guatemala and Honduras.
The easiest way to tell the difference between the three species is by looking at the femora of their front legs. The femur of S. incognita is big and round on one end, but is much narrower on the other-kind of like a caveman's club. The femur of S. complexa is similar, but the big end is not as large, making it look more like a baseball bat. Finally, the femur of S. integra is nearly the same size on both ends, making it look more like a stickball bat.