Bioacoustics of Neoconocephalus spiza

Bioacoustics.— N. spiza and N. cf. spiza are the only Costa Rican species of the genus with a call consisting of individual, discontinuous chirps. Individuals from northern Costa Rica ( Santa Rosa National Park) exhibit calling behavior indentical to that of Panamanian populations of N. spiza . Their call consists of long sequences of chirps produced at the rate of about 3-5/s (at 27°C), each chirp (pulse train) lasting 30-32 ms (avrg. 45±72, n=50). The chirps have recognizeable structure ( Fig. 56 G). Walker and Greenfield (1983) measured the wingstroke rate of individual chirps of N. spiza at ca. 150/s, with 6-8 wingstrokes per chirp. The peak of energy of the call is located between 10 and 11 kHz. Individuals from southern Costa Rica produce chirps at the rate of 3.2/s at 24°C ( Fig. 56 E) and unlike N. spiza from Panama ( Fig. 56 G), individual chirps have no recognizable structure ( Fig. 56 F). The stridulatory file in both forms is similar ( Figs. 44 F-G). Costa Rican individuals of both N. spiza and N . cf. spiza call both at night and during the day. Greenfield (1988) demonstrated that males of N. spiza will cease their calling if other species of the genus call nearby, and females stop moving towards the singing male if congeneric males also sing. In places where populations of congeners are high, males of N. spiza will switch their calling periodicity from nocturnal to entirely diurnal. This behavior is presumably caused by the avoidance of energy wasted on calling while the females cannot be attracted. It is yet unknown if such behavior occurs also in the Costa Rican population.

Diagnostic description.— General characteristics as described above. Stridulatory file of male 1.8-2.3 mm long, with 68-96 teeth; file strongly but gradually narrows towards proximal end ( Figs. 44 F). Mirror of stridulatory apparatus oval ( Fig. 45 D). Fastigium of vertex separated from fastigium of frons by distinct gap; ventral fastigial tooth prominent ( Fig. 13 H); frontal portion of fastigium with light band, usually accompanied by black band below; often (especially in brown specimens) entire ventral portion of fastigium black ( Fig. 13 G). Mid femur with 1-2 small spines on anterior ventral margin, never accompanied with black spots at their bases; fore femora occasionally unarmed ventrally. Brown individuals often with dark stripe on tegmina, continuous with darker lateral lobes of pronotum. Ovipositor slightly longer than hind femur (ratio ovipositor/hind femur 1.16-1.22), straight. 1.08), straight. Measurements .— Table 7 .

Note: Some Costa Rican specimens identified in this work as N. spiza may, in fact, represent a new, undescribed species. Although morphologically indistinguishable, and with the general song structure resembling that of individuals from Panamanian populations, the structure of individual chirps of the call differ significantly from “typical” N. spiza . All individuals of N. spiza from numerous localities in Panama and northern Costa Rica produce chirps with a distinctive pulse structure and chirps are seldom produced at a very regular rate for very long (usually no longer than several seconds, or 8-10 chirps; this applies to both chorusing and solo individuals) (Greenfield, pers. comm.). Contrastingly, individuals from southern Costa Rican populations (Osa Peninsula, Valle de Coto Brus) produce chirps without a recognizable pulse structure and chirps are produced at very regular rate for long periods of time. On the other hand, Greenfield (pers. comm.) suggests that N. spiza may be a species exhibiting a considerable inter-population variation in the song structure, and the differences between southern Costa Rican and Panamanian populations are due to such local variations. A similar suggestion was made by Walker and Greenfield (1983) with regards to N. saturatus (Griffini) from Trinidad . For the purpose of this work, I will treat the southern Costa Rican population as a possibly separate, unidentified species (it will be further referred to as N. cf. spiza ), closely related to N. spiza , without officially describing it as new, pending a more thorough analysis of a larger sample of specimens and recordings. The description below is based on Costa Rican specimens of N. spiza displaying acoustic behavior similar to that of Panamanian populations of this species.