Correction Statement: Naming conventions were incorrectly modified for the Early View publication and have been corrected for final issue placement. Specifically, flat-wing, flat wing, curly-wing, and curly wing have now been corrected to their proper nomenclature of flatwing and curlywing. We apologize to the authors and our readers for this error.

Located in the forelegs, katydid ears are unique among arthropods in having outer, middle, and inner components, analogous to the mammalian ear. Unlike mammals, sound is received externally via two tympanic membranes in each ear and internally via a narrow ear canal (EC) derived from the respiratory tracheal system. Inside the EC, sound travels slower than in free air, causing temporal and pressure differences between external and internal inputs. The delay was suspected to arise as a consequence of the narrowing EC geometry. If true, a reduction in sound velocity should persist independently of the gas composition in the EC (e.g., air, CO2). Integrating laser Doppler vibrometry, microcomputed tomography, and numerical analysis on precise three-dimensional geometries of each experimental animal EC, we demonstrate that the narrowing radius of the EC is the main factor reducing sound velocity. Both experimental and numerical data also show that sound velocity is reduced further when excess CO2 fills the EC. Likewise, the EC bifurcates at the tympanal level (one branch for each tympanic membrane), creating two additional narrow internal sound paths and imposing different sound velocities for each tympanic membrane. Therefore, external and internal inputs total to four sound paths for each ear (only one for the human ear). Research paths and implication of findings in avian directional hearing are discussed.

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A kindred on the mid-Atlantic island of St. Helena has severe "knock knees" and variable lesser malalignment at the elbows and wrists. The disorder is the consequence of hypoplasia of the corresponding bony condyles, with subsequent progressive degenerative osteoarthrophy. Inheritance is autosomal dominant and the condition seems to be a private syndrome which has arisen on the island by recent mutation. In view of the geographical localisation of the disorder and the anatomical distribution of the abnormalitites, we propose the title "St. Helena Familial Genu Valgum".