Eumecopoda pumila, Morris & Ingrisch & Willemse & Willemse & De Luca & Klimas, 2025

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 : 27-31

Eumecopoda pumila sp. nov.

( Figs 20 , 21 , 26 –29, 32, 82CD)

Specimens studied. Holotype male: “ 29.viii.1981 Mt. Kaindi lower slopes PNG ”, “nr Wau PNG 81-3 coll. G.K.Morris ” (Depository NBC Leiden) ; Allotype female: as first label of holotype (Depository NBC Leiden) ; Paratypes: PNG nr Wau, Mt. Kaindi , 1.viii (one male) & 19.viii (two males).1981, G.K.Morris; PNG, Wau W.E.I., 21.viii 1981 G.K. Morris (1 male) .

Additional paratypes: Papua New Guinea, Madang District, Kaironk , Dec. 1971 – Jan. 1972 Coll. J.I.Menzies (two males) ; New Guinea, Uniba, Upper Minj River Valley , Western Highlands , ca 6200 ft, 17.viii.1963. W.Vink (1 male 1 female) .

Description. Male.—As type species of genus but appearing smaller with shorter and relatively broader elytra and wings ( Figs 20 , 21 ). Fastigium verticis transverse, truncate anteriorly, faintly depressed from above. Pronotal disc strongly divergent, flat, lateral margins deeply cut by transverse sulci, anterior margin ranging from weakly concave to very slightly convex, posterior margin broadly rounded with or without a very obtuse median tubercle. Thoracic auditory spiracle narrows, elliptical, comparatively large (as in type-species), greatest diameter (height) 1.3 mm, hidden by ventroposterior part of pronotal metazona.

Tip of elytra, when flexed, ranging from not quite reaching to just surpassing tip of hind femur; tip of hind wings commonly not extending beyond elytra, at most scarcely beyond it. Elytron relatively wide, anterior edge apically strongly convex, posterior edge apically also strongly recurved but further apically scarcely sinuate, both edges creating apically a reduced pointed tip. Stridulatory area triangular, as in type-species; left elytron with file of normal shape, slightly fusiform, weakly concave horizontally and vertically, distance between most proximal tooth and distal tooth 3.1–3.2 mm, widest teeth in mid-part 0.33–0.34 mm, spacing widest in mid half about 8–9 teeth per 0.25 mm, total number of teeth 104–111; most of stridulatory area of right elytron transparent, ‘mirror’ speculum elongate elliptical and strongly depressed towards its posteroapical angle and there covered dorsally by strongly sclerotized but not inflated shell-shaped cantilevered fold (OMF), with straight to slightly convex outline. Hind wing also short and wide; anterior edge strongly curved apically; posterior edge remarkably convex, tip at distal end of MPa ( Ragge 1955) not or only obtusely pointed; stronger sclerotization of tip and distal part of MPa area scarcely present. Legs and abdominal terminalia as in type species, but smaller. Coloration as in type species, commonly quite dark brown.

Female.—As male, slightly larger.

Measurements. (Length in mm) (male n = 8; female n = 2): body male 21.0–25.0, female 27.0–28.6; pronotum male 6.0–6.2, female 7.0–7.5; elytron male 31.0–34.0, female 40.5–43.1; max. width elytron male 11.3–14.0, female 15.5–17.8; hind femur male 28.0–30.0, female 34.8–35.0; ovipositor 19.0–21.0.

Etymology. Named for its size, pumilus = dwarfish.

Distribution. Known from the districts of Morobe, Madang and W. Highlands, NE New Guinea.

Habitat. Perches to sing beside forest paths on low vegetation.

Comments. The new species is readily recognizable from all other taxa of the genus and especially from sympatric E. cyrtoscelis by its smaller dimensions and the relatively short elytra and wings which scarcely reach the tip of the hind femora and show a blunt apex, the very tip of the elytra located more posteriorly. The elytra in E. cyrtoscelis (length male 47–62, female 64–69 mm) surpass the tip of the hind femora (length hind femur male 38–44, female 46–51mm) ranging from almost to ample pronotal length, while the hind wings commonly extend clearly beyond the apex of the elytra when flexed.

Stridulation. The stridulatory apparatus of E. pumila differs from that in E. cyrtoscelis : the file in the latter commonly slightly longer (2.9–3.9 mm), slightly wider (0.35–0.4 mm), with fewer teeth (53–68), these more widely spaced (4–5 per 0.25 mm) and more robust. Bouts of steady stridulation lasting several seconds ( Fig. 32A ) are interrupted with pauses of a second or so. Listening to the playback of a recorded signal slowed by a factor of 8, one is aware that between each loud ‘oink-like’ squeal is another lower frequency sound. In real time in the field the insect sounds raspy, like a rough running motor, but it is nevertheless a resonant stridulator emitting a fairly long sinusoid wave train ( Fig. 32B, C ) with a Q 10 of 5 calculated from the spectrum of Fig. 32F . The most intense of these trains—a pulse—shows a stereotyped amplitude envelope ( Fig. 32B, C ) which builds, maximizes then falls away more slowly than it builds; this pulse precedes a drawn out decay ( Fig. 32C ) which is in turn followed by the quiet pulse ( Fig. 32C,E ). Slow rise and fall is perhaps contributing to reduced transient distortion as was the case in E. cyrtoscelis .

Most call energy is in the low audio, centred on 7 kHz ( Fig. 32H ) hence loud to human ears. E. pumila ( Fig 32 FGH) show a frequency modulation of about 2400 Hz—between 4.6 kHz and 7.1 kHz; compare Figs 32D and 32E . There is a very weak sound peak at 20 kHz ( Fig. 32H ) but no relevant ultrasonics. Unlike E. cyrtoscelis in E. pumila a harmonic relationship is not apparent between the audio peaks, but again the insect makes two low audio range resonant pulses typical of resonant stridulation. The specimen whose song was used in the figure consistently produced a low amplitude pulse between each major pulse, but this was less well defined in a second singer we recorded.

Figures

FIGURE 20. Male Eumecopoda pumila sp. nov., Habitus in dorsal aspect, smaller of the two Eumecapoda spp.

FIGURE 21. Eumecopoda pumila sp. nov.: A) Habitus in dorsal view, male holotype; B) Habitus in lateral view, male paratype; C) Habitus in lateral view, female allotype.

FIGURE 26. Eumecopoda pumila (SEM), strigin file; anal region of left tegmen, file vein bent abruptly 90° at cubitus, FIGURE 27. E. pumila (SEM), close-up of low broad midfile continuing as large toothless scraper blockage (BB). teeth.

FIGURE 32. E. pumila acoustic analysis: A) Coarse time resolution of one complete time-domain emission amid parts of two others; B) 5 phonatomes, each pairing a more sustained more intense pulse with a fainter less stereotyped following pulse; C) higher resolution of one complete phonatome from B shows sinusoid nature of pulses; D,E) [arrows from C] indicate higher resolution sinusoid waveforms at two audio frequencies; F,G) Fourier power spectra of D and E time samples respectively, F a high-Q peak of 6.9 kHz for more intense pulse, G a high-Q peak of 4.5 kHz for less intense pulse; H) Spectrum of multi phonatome time sample in B shows both low-audio frequency peaks.