Tibicen winnemanna, Male: Lateral view
Garner, Wake Co., NC (Sept 2008)
Collected ~7:15 PM EDT while "singing" the typical winnemana/pruinosus-like call (Eeee-Ooooo..Eeee-Ooooo...etc.).
Same specimen in the pic below (individual at top of pic)
Diagnostics such as the "line bisection test" & "wing node position" used to separate T. linnei from T. pruinosus in the Midwest - seems to be challenged when applied to "T. pruinosus/winnemanna" (+ other taxa) in the Southeast. I have noticed that while the point of bisection varies in T. winnemanna and T. pruinosus from the upper mid-South, it nearly always bisects the designated wing cell somewhere across the last half or third. This point of bisection is often very near, on the point of coalescence, and in some cases even anterior to the point of coalescence between the C (costal vein) & SC (subcostal) - a characteristic predicted for T. linnei. Midwestern conventions and use of this test suggest little if any bisection of the designated wing cell at all in members of the pruinosus group.
PLEASE REFER to the following reference site: incl. Specimen Key with images (9)
Key to the cicadas of Michigan
In support of the test, the point of bisection is "relatively consistent" in most T. linnei and crosses the halfway point nearly everytime either on the point of coalescence (in females) or anterior to the point of coalescence (usu. males).
NOTE: Some variation exists between males and females of T. linnei and among populations of T. linnei. The "line bisection test" is not an ABSOLUTE. Even for T. linnei, there have been populations and isolated specimens which DO NOT conform nor meet the expected test results!
Although this test has some support and validity in the upper Midwest, it is of little use if you wish to separate female specimens of T. winnemanna, T. pruinosus and T. linnei collected below the Mason-Dixon Line. Using this character and test, as a stand alone deciding factor, may result in erroneous identification.
Costal Margin used in id!
Please refer to the follwing paper for discussion on the idenification of T. linnei and separation of this species from other related species.
See page 226 for bend discussion!
According to Beamer and supported in other manuscripts, the shape of the opercula of the males in T. linnei is the ONLY true deciding factor, not the wing shape. I have had this discussion with several leading cicada specialists and none of them weigh heavily on the costal margin diagnosis any longer for identification of linnei or separation of it from similar related types.
Bowing in the costae and use of the "line bisection test" for species determination can fail. There is significant overlap in this trait and strong bowing in the costae can be seen in any of the following taxa: T. linnei, T. pruinosus, T. winnemanna and T. canicularis (to a lesser extent T. robinsonianus). Due to overlap, it is not possible to separate the species based on this character alone!