Ultrasonic songs and stridulum anatomy of Asiophlugis crystal predatory katydids (Tettigonioidea: Meconematinae: Phlugidini)

ABSTRACT

The behavioural ecology of ultrasonic-singing katydids is not well understood, and the general bioacoustics, barely known for a few Neotropical Meconematinae, tends to be overlooked for species from Southeast Asia. These include Asiatic species of Phlugidini, commonly known as crystal predatory katydids. One of its genera, Asiophlugis consists of 16 species for which acoustic signals and stridulum anatomy are broadly unknown. These characters can be used to understand species boundaries. Here, we sampled Asiophlugis from five sites in Malay Peninsula and Borneo Island, recorded the acoustic signals of five species plus one subspecies using ultrasound sensitive equipment, and examined their stridulum anatomy. The calling songs of the taxa involved were documented for the first time. We found that the stridulum anatomy (e.g., tooth distributions, tooth length and tooth density) is distinct between species but less so between subspecies. In contrary, songs of different taxa are different based on acoustic parameters (e.g., pulse duration, peak frequency) and descriptive patterns, even between the subspecies. We also did not observe that song signals are more different in sympatry than in allopatry. Whether this can be generalised requires further sampling, highlighting the need for more research on the ultrasonic acoustic communication in Asiatic katydids.

KEYWORDS:

• Bioacoustics
• carrier frequency
• Southeast Asia
• stridulatory file
• taxonomy
• predator

Acknowledgements

The authors are thankful to Huiqing Yeo and Xingbao Jin (in Singapore and Brunei Darussalam), Siew Tin Toh (in Pulau Tioman and Sandakan), Amira Aqilah Muhammad and Sofwan Badr (in Ulu Gombak), Momin Binti, John Lee Yukang and Saudi Bintang (in Sandakan) for field assistance. The permissions for collecting material were granted by the Forestry Department, Ministry of Primary Resources and Tourism, Brunei Darussalam (JPH/PDK/01 Pt 2); the Sabah Biodiversity Centre (JKM/MBS.1000–2/3 JLD.3 (99)) (for Sandakan); the National Parks Board (NP/RP18–064), Singapore; and the Research Promotion and Co-Ordination Committee, Economic Planning Unit, Prime Minister’s Department (UPE: 40/200/19/3395), Malaysia and the University Malaya (for Pulau Tioman and Ulu Gombak).

Author contributions

MKT and FMZ contributed equally to this study.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

The work of MKT was supported by the Lady Yuen Peng McNeice Graduate Fellowship of the National University of Singapore; the Orthoptera Species File Grant 2019 under the taxonomic research project titled “Contribution to the species diversity and acoustic data on Orthoptera from Sandakan (Borneo, East Malaysia, Sabah)”; and Percy Sladen Memorial Fund (The Linnean Society of London) under the project titled “Advancing biodiversity informatics of Orthoptera from Brunei Darussalam”. The work of FMZ was also supported by the Leverhulme Trust Grant RPG–2014–284.