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Order Orthoptera is one of the largest group of insects and is well-distributed all over the world. Against a documented diversity of 28,090 species worldwide, only 1630 sound recordings are available. In India, 1033 species of Orthoptera are described taxonomically, consisting of 231 sp. gryllids (142 endemic sp.) Owing to its biogeographical diversity India holds the potential for diversity of acoustic signals of field crickets. The acoustic signals have been recorded predominantly from the southern part of the country. Hence, the study was undertaken to investigate acoustic diversity of field crickets from different biogeographic regions in India, to analyse call differences between species. The study was carried out from August 2014 – April 2017. The acoustic sampling was carried out after sunset between 7 – 10 pm, the peak calling time of crickets. The calling males were tracked and located by their calls. All the recordings were made using digital recorder Tascam DR-100MKII at 44.1 kHz and Sennheiser ME66 shotgun microphone. The recorder was held at a distance of 20-25 cm away from the calling individual. Temporal and spectral analyses were performed using signal processing Software RAVEN Pro 1.4 (Cornell Lab of Ornithology, Ithaca, NY) and Spectra PLUS-SC (Pioneer Hill Software, Poulsbo, WA). The acoustic characterization was based on syllable period, syllable duration, chirp period, and chirp duration. A total of 47 different calls were recorded from the different regions of the country. Of the 47 recorded calls, 40 calls species were chirping and 7 calls species were trilling. All the recorded calls belonged to superfamilies Grylloidea and Gryllotalpoidea. 38 calls types were found to be narrow banded with the dominant frequency ranging 2-8 kHz. The present study also highlighted species with narrow range of distribution of certain species. Xenogryllus sp. was only recorded from Northeast region in monsoon. Itaropsis sp. was recorded from different regions that has only been described from southern part of the country. Tarbinskiellus sp. have shown the inter-regional differences. The present study aims to bridge the gap of acoustic inventory of the grylloids from different biogeographical region of India. This would help in biodiversity documentation and aid in development of non-invasive bioacoustic method for biodiversity assessment, monitoring on Indian Orthoptera.
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