Gnathoclita vorax (Stoll, 1813)

Hugel, Sylvain, 2019, Panoploscelis scudderi Beier, 1950 and Gnathoclita vorax (Stoll, 1813): two katydids with unusual acoustic, reproductive and defense behaviors (Orthoptera, Pseudophyllinae), Zoosystema 41 (17), pp. 327-340 : 336-339

Gnathoclita vorax (Stoll, 1813)

Gryllus (Acheta) vorax Stoll, 1813 : plate 4c, figs 19, 20.

Gryllus (Gnathoclita) vorax De Haan, 1843: 208 .

TYPE MATERIAL. — Lost?

TYPE LOCALITY. — America

OTHER MATERIAL EXAMANED. — French Guiana. Planète revisitée Guyane 2015, Monts Tumuc-Humac, Massif du Mitaraka, 54.450137° O, 2.233883°N ( GF DZ), 315 m a.s.l.; 23.II-10. III.2015, nuit, 1 ♂, MNHN. — Planète revisitée Guyane 2015, Monts Tumuc-Humac, Massif du Mitaraka, Layon D, 54.4509° O, 2.2357°N, 280 m a.s.l. – 54.4517° O, 2.2338°N, 293 m a.s.l., 23.II- 10.III.2015, nuit, 1 ♂, 1 ♀, MNHN. — Planète revisitée Guyane 2015, Monts Tumuc-Humac, Massif du Mitaraka, vers sommet en Cloche, 54.4541° O, 2.2349°N, 370 m a.s.l., - 54.4646° O, 2.2329°N, 470 m a.s.l., 23.II-10.III.2015, nuit, 1 ♂, 1 ♀, MNHN .

DISTRIBUTION. — Surinam, Guiana, Brazil North [Cigliano et al., OSF, 2018], French Guiana.

REDESCRIPTION

Males and females of this species have been comprehensively redescribed ( Willemse 1954, Beier 1960, De Jong 1971).

Stridulatory apparatus ( Fig. 7D, E )

Left FW mirror infuscated, with no concavity, oval shaped except the anterior proximal angle; about 2 times as high (maximal height) as wide (maximal width). File with c. 101 lamellar teeth ( Fig. 7E ).

BIOACOUSTICS ( FIG. 7 A-C, SUPPLEMENTARY VIDEO 2) Gnathoclita vorax sings by night hours, from the undergrowth from plant-made cavities. The call consists of long (> 1 min) relatively regular repetitions of syllables. At 26°C, syllables are repeated every 3.818± 0.625 s (syllable duration: 50.8±4.3 ms). The frequency peaks between 8750-8900 Hz.

Comparison of G. vorax and G. sodalis Brunner von Wattenwyl, 1895 male call

The call of G. sodalis is made of phonatomes repeated every 180-480 ms, depending on the temperature (Montealegre-Z & Morris 1999) whereas G. vorax phonatomes are repeated every c. 4 s. The call of G. sodalis peaks at about 15-16 kHz, about twice the frequency of G. vorax peak (Montealegre-Z & Morris 1999). Interstingly, in addition to acoustic communication, G. sodalis males use tremulatory vibration to communicate with other males and females ( De Souza et al. 2011). This tremulatory behavior may not occur in G. vorax since males of this species sing in a very narrow environment (see below).

GUARDING BEHAVIOR OF GNATHOCLITA VORAX

A total of five males of Gnathoclita vorax were observed during the Mitaraka survey in 2015. All these observations occurred late by night hours (11 pm-2 am). These males were sheltering in narrow tube-shaped hollow plant sections, their head facing the aperture of the cavity ( Fig. 7 A-D). The diameter of these shelters was hardly larger than a male’s head, preventing turn-overs ( Figs 7D , 8 ). The shelter of all but one specimen was within hollow dead stems of Astrocaryum sp. These observations are in line with a previous report of Gnathoclita vorax singing from within Gadua sp. bamboo stems ( Naskrecki 2008).

Three of the five males observed were located owing to their loud syllables repeated every 5 s ( Fig. 7 A-C). These males were stridulating alone within their shelter, their antennae protruding from the entrance.

The two other males were found owing to their conspicuous antennae protruding from the aperture. None were stridulating. In both cases, an adult female was localized at the bottom of the tube-shaped shelter, behind the male who blocked the entrance ( Fig. 8 A’). None of the females had a spermatophore attached.

These specimens were kept separated for one week, and subsequently placed altogether in a large cage containing wood-made tube-shaped shelters of similar measurements to those observed in the field. Every morning, the localization of the females was checked. During the five first days together with the males, both females were observed as in the field: at the bottom of the shelter, a male blocking the entrance. Unfortunately, we have not been able to observe whether the female entered the shelter after mating, and whether the male was actively driving her. After five days, both specimens were forced out of the shelter; only males returned to the shelter during the subsequent days and restarted to stridulate during nights.

These observations suggest that males of Gnathoclitha vorax display a form of mate guarding. Such a behavior was never formally observed in Tettigoniidae ( Gwynne 2001) , although a possible type of male guarding behavior was recently reported in Oncodopus and Colossopus ( Unal & Beccaloni 2017) .

The function of mate guarding has extensively been discussed in Grylloidea ( Simmons 1990; Sakaluk 1991; Hockham & Vahed 1997; Bateman & MacFadyen 1999; Wynn & Vahed 2004; Bussiere et al. 2006; Parker 2009; Parker & Vahed 2009) and this behavior was shown to prevent the female from removing the spermatophore of a Gryllidae species ( Hockham & Vahed 1997). Since females had no spermatophore attached within the shelter, the mate guarding of Gnathoclitha vorax was rather recalling the burrow sharing occurring in some Grylloidea, such as Gryllus campestris (Rodriguez-Munoz et al. 2011) . In this latter species, the burrow sharing was shown to protect from predation and increase mating of paired males).

Figures

FIG. 7. – Call of Gnathoclita vorax Beier, 1950: A-C, Field recording of a male calling from a cavity (26°C); D, male stridulatory apparatus in dorsal view; E, male file in ventral view. Scale bar: D, 5 mm; E, 2.5 mm.

FIG. 8. — Shelters of Gnathoclita vorax (Stoll, 1813) in the field: A, the face of a male in visible within a hollow shaft of Astrocaryum Meyer, 1818 leaf, antennae protruding from the entrance; A’, when an aperture is made on the shaft, a female is visible behind the male (at the time of the picture, the male was already col- lected); B, entrance of a shelter (male removed); C, disturbed male escaping from the shelter; D, picture of the male singing in A-C during the call.