Singers in the grass: call description of conehead katydids (family: Tettigoniidae) and observations on avoidance of acoustic overlap

Abstract

ABSTRACTThe sub-family Conocephalinae constitutes one of the richest groups of katydids in terms of diversity and distribution. Tropical katydids especially in India have largely escaped academic attention. Here, we record and describe call patterns for six conehead katydids from India: Conocephalus melanus, Conocephalus sp X, Euconocephalus indicus, Euconocephalus mucro, and Euconocephalus sp Y from North-Eastern Himalayas and Euconocephalus pallidus from the Western Ghats. All the species showed broadband frequency spectra (10.5–42.4 kHz), and three of the six species showed high rates of calling (289–453 syllables/s). We observed that the co-occurring call types never called at the same time or from the same location. We hypothesized this partitioning between call types is due to similarity in their calls; we used non-metric multi-dimensional scaling (NMDS) to investigate patterns of temporal or habitat-partitioning that some of the co-occurring call types exhibited during the course of study. The co-occurring Euconocephalus sp Y and E. mucro with high degree of overlap and similarity in their calls exhibited partitioning on a spatial scale. Conocephalus sp. X and C. melanus with distinct calling activity peaks formed separate clusters based on temporal call structures. As females rely heavily on spectral qualities, we speculate partitioning on temporal scale to avoid heterospecific interference due to similar spectral properties between the two call types.