Bioacoustics of Conocephalus (Anisoptera) cinnamonifrons

Measurements. Taken from male holotype : body length alive 17 mm (inferred from photo), pronotum 3 mm , tegmina 7 mm , mirror of left tegmen 1 mm long, hind femora 12 mm . Habitat and phenology. Found in herbaceous vegetation and understory of woodland near the shore of the Río de la Plata, as well as around a lagoon and on wet, structurally complex meadows a few kilometers inland (before the current drought partly inundated and with pools), and also recorded from Entre Ríos close to the Uruguay River ( Fig. 4A,B ). Perhaps a specialist of riparian ecotones. Adults appear late in summer, February to May. Behaviour and song. Much more wary than the common Conocephalus longipes , always ready to hide. Active at day and night. The calling song of the captured individual was recorded after midnight, but males most probably also sing during the day, which is common among congeners (as far as known in all species). This holotype male called continuously, with long syllable trains alternating with short sequences consisting of a few sparse syllables ( Fig. 2A–C ). The long syllable trains varied in length from 2 to 10 seconds, with a syllable repetition rate of 41–42 per second at 23°C. The uniform short sequences lasted less than one second and constantly consisted of 5–8 syllables, mostly 7. The corresponding syllable repetition rate would be 10 per second. The very broad carrier frequency spectrum is located entirely in the ultrasound, from above 20 kHz to 60 kHz, with most energy between 30 kHz and 40 kHz ( Fig. 2D ).

Diagnosis. Head light brown (green in the majority of South American Conocephalus species ), lateral lobes of pronotum, thoracic pleura, mid femora and basal half of hind femora green, otherwise light brown, eyes brown, tips of hind femora not darkened, vertex with reddish medial band, pronotum with light medial band with thin, undulate reddish borders, abdomen in both sexes plain ( Fig. 2E , Fig. 3A–C ). Fastigium narrow, in dorsal view half as wide as scapus and barely wider than pedicellus, very little restricted ahead of apex. Prosternum with a pair of short and delicate spines. Tegmina in males slightly longer than twice the pronotum length, in females shorter (1.5–1.6 times pronotum length), stridulatory area as in Fig. 1C . Hind femora with 3–5 irregularly spaced ventral spinules in distal half. Male cerci typical of the genus ( Fig. 1D ). Females with relatively short, somewhat broadened, and distinctly upcurved ovipositor ( Fig. 3A ; all other known Conocephalus females from South America have straight or almost straight ovipositors).