How Did E. M. Walker Measure the Length of the Labium of Nymphs of \u3ci\u3eAeshna\u3c/i\u3e and \u3ci\u3eRhionaeschna\u3c/i\u3e (Odonata: Aeshnidae)?

The exhaustive studies of nymphs of Aeshna Fabricius and Rhionaeschna Förster by E. M. Walker (1912-1958) have long guided the taxonomy of these groups and formed the basis for keys still in use today. However, uncertainty about how he measured the length of the labium, including the varied terminology he used over the duration of his career concerning this structure, has led to confusion about application of his taxonomic recommendations. We recalculated ratios of the maximum width/length [W(max)/L] by measuring the illustration dimensions of folded labia and prementums in publications throughout his career and compared these data with the ratios he stated in those publications and with ratios derived from measurements of specimens in our collections. Our results show that from 1912 to 1941, Walker restricted length measurement to the prementum proper (which he called the “mentum of the labium”), exclusive of the ventrally visible portion of the postmental hinge. However, in 1941 he reported ratios from length measurements done two ways, excluding the postmental hinge in his description of the nymph of A. verticalis Hagen, but including the hinge in his description of the nymph of A. septentrionalis Burmeister (Whitehouse 1941). In Walker’s most recent and influential work (1958), he included the postmental hinge in labium length measurements of nine species, but restricted length measurements to the prementum for five others. He was consistent with the use of terms, using both “folded labium” by which he meant the prementum plus the postmental hinge, and “prementum” by which he meant only that structure. However, Walker’s descriptions of the labium in his latest work are buried in long, frequently punctuated sentences that for most species include the terms “folded labium” and “prementum” in the same sentence, so careful reading is required to know which term is intended in the width/length ratio. Width/length ratios we each calculated independently were invariably similar for a given species and were usually similar to Walker’s stated ratio for that species. These similarities affirm our conclusion that while labium measurements must be done with care, they are closely repeatable among workers and will consistently lead to correct determinations in properly designed couplets of dichotomous keys to these genera. We recommend measuring the length of the prementum proper in future studies of these genera when labium ratios are calculated because we found less variability in those cases than when the measurements included the postmental hinge. An approximate conversion between the two methods of calculating W(max)/L ratios can be made as follows: ratio calculated when the length of the prementum excluding the postmental hinge is used x 0.88 is approximately equal to the ratio when the postmental hinge is included for species of Aeshna and Rhionaeschna in North America

Efficacy of Morphological Characters for Distinguishing Nymphs of \u3ci\u3eEpitheca Cynosura\u3c/i\u3e and \u3ci\u3eEpitheca Spinigera\u3c/i\u3e (Odonata: Corduliidae) in Wisconsin

Attempts to distinguish exuviae and last-instar nymphs of Epitheca cynosura (Say) and Epitheca spinigera (Selys) (Odonata: Corduliidae) using lateral spine characters have proven to be unreliable, and recent use of setae counts on only one side of the prementum or one labial palp have led to confusion because these structures often hold unequal numbers of setae on the two sides of the same specimen. Based on exuviae of 67 reared E. cynosura and 55 reared E. spinigera from lakes throughout Wisconsin, we tested the efficacy of previously used character states for distinguishing these species and searched for new characters to improve the reliability of regional keys. The most reliable diagnostic character was the combined number of setae on both sides of the prementum and on both labial palps (≤ 35 – E. cynosura; ≥ 36 – E. spinigera), which correctly determined 96% of our specimens. For the small percentage of specimens that lie in the region of overlap in total setae number, we found that total exuviae length, cerci ÷ epiproct ratios of females, tubercle distance ÷ epiproct ratios of males, and the shape of the dorsal hook on segment 8 could be used to strengthen determinations

First Records for \u3ci\u3eAeshna Sitchensis\u3c/i\u3e (Odonata: Aeshnidae) and \u3ci\u3eEnallagma Clausum\u3c/i\u3e (Odonata: Coenagrionidae), and a Northwestern Record for the State-Endangered \u3ci\u3eSomatochlora Incurvata\u3c/i\u3e (Odonata: Corduliidae) in Wisconsin

While surveying for Odonata in coastal peatlands and associated shoreline areas adjacent to Lake Superior in Wisconsin, we documented populations of two new state record species, the zig-zag darner (Aeshna sitchensis Hagen) and the alkali bluet (Enallagma clausum Morse). We also located a robust population of the state-endangered incurvate emerald (Somatochlora incurvata Walker) at the northwestern edge of the known range of this species. Adults and exuviae of A. sitchensis and S. incurvata were found at an insular fen on Stockton Island, Ashland County, within the Apostle Islands National Lakeshore (AINL). Breeding of both species had occurred in areas of the fen where small pools had dried by summer. Additionally, a single adult male A. sitchensis was collected in the City of Superior in Douglas County. Adult E. clausum were found at two sites: on the Lake Superior beach near the mouth of the Sand River within the AINL in Bayfield County, and along the northeast shore of Allouez Bay in the City of Superior in Douglas County

How Did E. M. Walker Measure the Length of the Labium of Nymphs of \u3ci\u3eAeshna\u3c/i\u3e and \u3ci\u3eRhionaeschna\u3c/i\u3e (Odonata: Aeshnidae)?

The exhaustive studies of nymphs of Aeshna Fabricius and Rhionaeschna Förster by E. M. Walker (1912-1958) have long guided the taxonomy of these groups and formed the basis for keys still in use today. However, uncertainty about how he measured the length of the labium, including the varied terminology he used over the duration of his career concerning this structure, has led to confusion about application of his taxonomic recommendations. We recalculated ratios of the maximum width/length [W(max)/L] by measuring the illustration dimensions of folded labia and prementums in publications throughout his career and compared these data with the ratios he stated in those publications and with ratios derived from measurements of specimens in our collections. Our results show that from 1912 to 1941, Walker restricted length measurement to the prementum proper (which he called the “mentum of the labium”), exclusive of the ventrally visible portion of the postmental hinge. However, in 1941 he reported ratios from length measurements done two ways, excluding the postmental hinge in his description of the nymph of A. verticalis Hagen, but including the hinge in his description of the nymph of A. septentrionalis Burmeister (Whitehouse 1941). In Walker’s most recent and influential work (1958), he included the postmental hinge in labium length measurements of nine species, but restricted length measurements to the prementum for five others. He was consistent with the use of terms, using both “folded labium” by which he meant the prementum plus the postmental hinge, and “prementum” by which he meant only that structure. However, Walker’s descriptions of the labium in his latest work are buried in long, frequently punctuated sentences that for most species include the terms “folded labium” and “prementum” in the same sentence, so careful reading is required to know which term is intended in the width/length ratio. Width/length ratios we each calculated independently were invariably similar for a given species and were usually similar to Walker’s stated ratio for that species. These similarities affirm our conclusion that while labium measurements must be done with care, they are closely repeatable among workers and will consistently lead to correct determinations in properly designed couplets of dichotomous keys to these genera. We recommend measuring the length of the prementum proper in future studies of these genera when labium ratios are calculated because we found less variability in those cases than when the measurements included the postmental hinge. An approximate conversion between the two methods of calculating W(max)/L ratios can be made as follows: ratio calculated when the length of the prementum excluding the postmental hinge is used x 0.88 is approximately equal to the ratio when the postmental hinge is included for species of Aeshna and Rhionaeschna in North America

The Puzzling Presence of Lestes australis (Odonata: Lestidae) in Wisconsin - Does This Species Migrate?

Lestes disjunctus australis Walker, 1952 was named as a subspecies of Lestes disjunctus Selys, 1862. In recent decades it has been considered deserving of full species status by most specialists. The core of its eastern North American range is south of Wisconsin, but during April through June of some years, mature individuals, and occasionally reproductive behavior, are observed at shallow ponds and wetlands mostly in the southern half of the state. Since first recorded in Wisconsin in 2002, it has been detected in 13 of Wisconsin’s 72 counties. However, there has been no unequivocal documentation of successful reproduction in the state. Various possibilities regarding long-range dispersal or facultative migration of this species and other species of Zygoptera are discussed

Ultra-low phase noise all-optical microwave generation setup based on commercial devices

In this paper, we present a very simple design based on commercial devices for the all-optical generation of ultra-low phase noise microwave signals. A commercial, fibered femtosecond laser is locked to a laser that is stabilized to a commercial ULE Fabry-Perot cavity. The 10 GHz microwave signal extracted from the femtosecond laser output exhibits a single sideband phase noise $\mathcal{L}(f)=-104 \ \mathrm{dBc}/\mathrm{Hz}$ at 1 Hz Fourier frequency, at the level of the best value obtained with such "microwave photonics" laboratory experiments \cite{Fortier2011}. Close-to-the-carrier ultra-low phase noise microwave signals will now be available in laboratories outside the frequency metrology field, opening up new possibilities in various domains.Comment: 8 pages, 3 figures. To be published in Applied Optics, early posting version available at http://www.opticsinfobase.org/ao/upcoming_pdf.cfm?id=23114

Damping rate of plasmons and photons in a degenerate nonrelativistic plasma

A calculation is presented of the plasmon and photon damping rates in a dense nonrelativistic plasma at zero temperature, following the resummation program of Braaten-Pisarski. At small soft momentum $k$, the damping is dominated by $3 \to 2$ scattering processes corresponding to double longitudinal Landau damping. The dampings are proportional to $(\alpha/v_{F})^{3/2} k^2/m$, where $v_{F}$ is the Fermi velocity.Comment: 9 pages, 2 figure

Algebraic characterization of the Wess-Zumino consistency conditions in gauge theories

A new way of solving the descent equations corresponding to the Wess-Zumino consistency conditions is presented. The method relies on the introduction of an operator $\delta$ which allows to decompose the exterior space-time derivative $d$ as a $BRS$ commutator. The case of the Yang-Mills theories is treated in detail.Comment: 16 pages, UGVA-DPT 1992/08-781 to appear in Comm. Math. Phy