Noisy neighbours among the selfish herd: a critical song distance mediates mate recognition within cicada emergences (Hemiptera: Cicadidae)

Cicadas probably experience mate recognition challenges as a result of the densities that may occur during adult emergence events, and in Okanagana, the most speciose genus of North American cicadas, high alpha diversities during protoperiodical emergences will exacerbate the mate recognition problem. Using 227 songs from 23 taxa, a linear plateau model regressed recognition potential, estimated from linear discriminant analysis, against song distance, revealing a critical song distance of 0.728 standard deviations in z-transformed song parameter space accompanied by a recognition of 91.6%. Based on detailed examination of museum specimen localities, field observations and habitat, taxa were classified as sympatric or allopatric. Sympatric species were separated by song distances that were significantly greater than this critical distance. As expected for mate recognition characters, little within-species variance was observed in the songs of most species, and the relationship between increases in syllable rate and improved recognition was one of diminishing returns. For several taxa that sang with extreme syllable rates of high variance, a mate recognition – sexual selection continuum is proposed. Along this continuum rapid rates simultaneously prevent mate recognition errors while signalling male quality to females.

Evaluation of multiaxial fatigue life prediction criteria for Ni-based superalloy GH4169

Fatigue tests under multiaxial loading were conducted on Ni-based superalloy GH4169 tubular specimens. The microstructures of fracture surfaces under different loading paths were compared. Several multiaxial fatigue criteria were reviewed and evaluated with multiaxial fatigue test data. The criteria of equivalent strain, maximum shear strain and Kandil–Brown–Miller provided unsatisfactory results for GH4169. Fatemi–Socie and Wu–Hu–Song parameters showed better life prediction abilities for this material. Minor modification has been introduced in Wu–Hu–Song parameter. The material constants of modified Wu–Hu–Song criterion are only dependent on torsional fatigue tests. The satisfactory prediction results based on modified Wu–Hu–Song model were obtained for GH4169.

Geographic and individual variation in the morphology and sequential organization of the song of the Savannah Sparrow (Passerculus sandwichensis)

Advertising songs of male Savannah Sparrows (Passerculus sandwichensis), from Ontario and Nova Scotia, were studied for patterns of species, regional, and individual distinctiveness. Using a five-category, alphabetic cataloguing scheme. species-typical patterns of song organization were found in the morphology of introductory (A and B) and trill (D) song sections. Using finite-state grammar analysis, regional variation was found in the sequential organization of song sections; regional differences were also seen in the morphology of trill (D) and terminal (E) song sections. Individual differences were detected in the structure of transition (C) sections between B and D, as well as between successive D sections, with no two C sections being alike. Regional variation was also seen in the morphology of C sections.The potential for C sections to act as individual as well as regional markers, and of trills to have both species and regional characteristics, suggests that a song parameter may be capable of carrying more than one type of identifying information.