Charisoma karschi, Bolivar, 1903

Morris, Glenn K, Ingrisch, Sigfrid, Willemse, Fer, Willemse, Luc, De Luca, Paul A. & Klimas, Dita, 2025, Stridulation songs of some Tettigoniidae (Ensifera, Orthoptera) from Papua New Guinea, Zootaxa 5600 (1), pp. 1-81 : 22-26

Charisoma karschi ‘goggle eye’ undescribed subspecies

( Figs 16 , 17B , 18B , 19 )

Specimens studied. Holotype male: “ PNG, Mt. Kaindi near Wau, 30 viii 1981, G.K. Morris ” (Depository NBC Leiden, missing).

Other specimen studied: 1 male (paratype) with similar labels as holotype (Depository NBC Leiden, missing) .

Description. Male.—General appearance as in Figs. 16 , 17 . Size smaller than nominate form. Fastigium of frons tubercle-like. Fastigium verticis transverse (1.2–1.3 mm), distinctly divided into right and left halves, each half consisting of a rounded tubercle-like inflation medially and a laterodorsally extending narrow fold which does not extend anteromedially ( Fig. 18B ). Eyes conspicuously globose, slightly stalked, in dorsal view greatest diameter of eye 1.1 mm of stalk 0.9 mm. Pronotum as in nominate form but smaller, surface impressopunctate, anterior margin very slightly rounded, posterior margin weakly excised, disc flat without lateral carinae, laterally roundly merging into lateral lobes, also in metazona. Thoracic auditory spiracle small, comparatively inconspicuous, not covered by pronotum. Prosternum with a pair of spines. Elytron scarcely reaching tip of hind femur, thick, somewhat rigid, convex with weak cubital hinge along stridulatory area; not transparent, archedictyon in basal half of elytron including all of costal area densely covered with numerous droplet-like semitranslucent areolae, in distal half increasingly striated with numerous elongate narrow semitranslucent tiny cells; elytron quite wide at base, anterior and posterior margins almost straight, the latter in apical third obliquely converging towards narrowly rounded tip; venation reduced to main veins, Sc and R rather divergent in basal third, convergent in mid third and almost touching each other there and thus creating a fusiform area, in apical third again weakly divergent and reaching tip of elytron; R with two or three pectinate branches, these and distal part of M running straight, parallel and at about similar distance from each other reaching the posterior margin. Stridulatory area folded along Cu1, triangular, venation of this area of left elytron consisting of archedictyon all over except for the file; file in dorsal view not inflated, in ventral view almost straight, concave in profile, slightly fusiform, shortest distance between most proximal and distal teeth 2.9 mm, greatest width in mid part 0.23 mm, number of teeth about 140, proximally closer set, spacing widest in mid third about 7 per 0.25 mm; stridulatory area of right elytron with large mirror which is longer than wide, elliptical with basal margin transverse and straight; fold of mirror narrow, extending slightly dorsoanteriorly over the depressed mirror, its outline almost straight.

Supra-anal plate simple, convex, posterior margin evenly rounded. Cercus slightly tapering apically, cylindrical, weakly incurved with a strongly incurved apical spinule. Subgenital plate narrowing posteriorly, hind margin with deep U-shaped excision, the posterior processes bearing quite short styli.

Tympana of fore tibiae narrow oval, completely open on either side. Fore coxa with dorsal spine, mid and hind coxa unarmed. Fore legs unarmed except for both knee lobes provided with a single spine each and presence of a tiny apical spine of dorsoexternal keel of tibia. Mid legs also with single-spined knee-lobes, ventral keels of tibia bearing some spines. Hind femur with a few spines in distal half of both ventral keels, knee-lobes also single-spined.

Coloration uniformly green except for eyes and tips of tibial spines dark brown and brownish flush over distal striated part of both elytra.

Female.—see below.

Measurements. (In mm) (male n = 2): body length 16.0 & 15.7; width of fastigium verticis 1.2 & 1.3; eye diameter 1.1 & 1.1 plus stalk 0.9 & 0.9; pronotum length 4.1 & 4.3; elytron length 13.5 & 15.1; max. width of elytron 7.0 & 6.7; mirror length 3.8 & 4.1 width 2.6 & 2.7; length strid. file 2.9 & 3.0, max. width of teeth 0.225 & 0.290, spacing in mid part 7 & 8 teeth per 0.25 mm, total number of teeth 138 & 143; length hind femur 13.2 & 13.0.

Distribution. Known only from Mt. Kaindi near Wau, Morobe District, NE New Guinea.

Comments. In fading evening light attention was drawn to this species by its calls. These came from trees bordering the repeater station atop Mt. Kaindi. The first male of two captured was taken by climbing 4–5 m up a tree. The singer was disturbed into silence by the climber several times, but readily returned to his song. He was secured by a clumsy grab that deprived him of a leg. A second male was collected later about 1 m from the ground, an anomaly of perch since no calling was heard coming from that low down.

The Mt. Kaindi males are apparently smaller than typical C. karschi and the lateral folds of the fastigium verticis do not extend towards the fastigium of frons. Differences of the stridulatory apparatus may refer mainly to smaller size of the elytra in C. karschi ‘goggle eye’ ssp. nov.

The difference in size, but particularly the remarkably distinct fastigium of vertex of the Mt. Kaindi specimens justify taxonomic recognition of the latter form.As further comparison of their songs is not yet possible, we propose to rank the new taxon at subspecific level, C. karschi ‘goggle eye’ ssp. n.

We have before us a single female from Koroba, Southern Highlands District 13 x 1960. Its size and fastigium of vertex disagree with the female of nominate C. karschi before us but fit perfectly these characters of C. karschi ‘green goggle’. By lack of an associated male, however, we abstain from further identification.

A photo available on the Orthoptera Species File ( Fig. 17A ) shows a dorsal view of the right tegmen sound field of the syntype male in the Madrid Museum. In this species there is only a very small cantilevered overmirror fold, spanning the anal margin of the somewhat rearwardly ovoid mirror speculum.

Stridulation. The song of Charisoma karschi ‘green goggle’ is a succession of well-spaced 5-train calls. Song period of a singer at 20°C was close to 1.2 s. One call is shown in Fig. 19A . It lasts about a quarter second and consists of 4–6 rather dense trains of pulses, most commonly 5. The first pulse train is lower in intensity and shorter in duration. The train period ( Fig. 19A ) is about 50 ms.

Because what we here term a pulse often overlaps its neighbours i.e., is not cleanly isolated by down time, the waveform of this insect’s stridulation has a ‘string of beads’ appearance ( Fig. 19C ). In each single train ( Fig. 19B ) we can count ~70 variably contiguous pulses. (See the 8 pulses of Fig. 19 BC.) The insect’s file has ~140 teeth. So one might guess that each ‘bead’ reflects scraper play across two teeth. (Alternatively, or in addition perhaps posit two specular oscillations per each tooth-scraper event?) As Fletcher (1992) says, if the slip rate of the scraper falls just below that needed for resonance, then slipping from one file tooth to the next “may take place before the vibration from the previous slip event has died away” ( Fletcher 1992). Pulses should then overlap. The overall effect is a great number of sinusoidal waves which repeatedly start and decay but never extend to a sustained resonance. This repeated onset and falling away would add side bands which would explain why the spectrum ( Fig. 19D ) tends toward a band rather than a high Q carrier.

Spectral frequencies occur in a high-audio band whose longer wavelengths begin sharply at 10 kHz ( Fig. 19D ); this carrier band remained intense to the beginning of the ultrasonic in one singer but rolled off appreciably in the other. The spectrum Fig. 19D is a FFT calculated upon the signal sample in B. The microphone in use for these records is a B&K 4135 attached to a 2203 sound level meter, so the spectrum above 40 kHz is inaccurate. But spectra made with the QMC recording system showed no sound energy above 40 kHz, so we have left the axis extending to 70kHz in the figure.

Figures

FIGURE 16. Charisoma karschi ‘goggle eye’ ssp. nov., male stands on finger.

FIGURE 17. A) Charisoma karschi Bolivar, 1903 male syntype, dorsal view of strigin of deployed tegmina, arrow to modest overmirror fold; photo from OSF; repository Museo Nacional de Ciencias Naturales, Madrid; B) Charisoma karschi ‘goggle eye’ ssp. nov. (F. Willemse intended holotype male).

FIGURE 18. Compared fastigia of vertex Charisoma spp. (scale 1 mm):A) C. karschi karschi Bolivar, 1903 lectotype male; B) C. karschi ‘goggle eye’ ssp. nov. (Fer Willemse intended holotype male).

FIGURE 19. C. karschi ‘goggle eye’ ssp. nov. acoustic analysis: A) One call from a steady sequence; B) Last pulse train of A at higher resolution shows ~70 variably recurring pulses; C) time sample from middle of train in B showing 8 pulses in more detail; D) Fourier power spectrum a 15-kHz wide band between 10 and 25 kHz, produced by, transient stridulation.