Mikrischyrum musicum, Braun, 2021

Braun, Holger, 2021, Mikrischyrum musicum, a new katydid species from montane rainforest in southern Ecuador with complex pure-tone calling song (Orthoptera: Tettigoniidae: Pseudophyllinae: Platyphyllini), Zootaxa 5067 (2), pp. 267-272 : 268-270

Mikrischyrum musicum sp. nov.

( Figs. 1–3 )

Braun 2002, pp. 72, 110 (song): Drepanoxiphus sp. , Pelzbeinschrecke [furry-legged katydid]; Braun 2008, p. 220: Brachyauchenus sp.

Etymology: Referring to the elaborate musical calling song of the male.

Specimens: All from Estación Científica San Francisco ( Ecuador, Prov. Zamora-Chinchipe, 1850 m, 3.971 S, 79.079 W) and collected by the author: male holotype, 6 i 2000 (cbt019s04, sound recordings) and female paratype, 13 i 2000 (cbt019s05), both deposited in the Museo de La Plata ( Argentina) , as well as 4 more female paratypes: 25 ix 1997 (cbt019s01), 30 vii 1998 (cbt019s02), 8 ix 1999 (cbt019s03), 25 i 2000 (cbt019s06), currently in collection of the author ( Germany) .

Diagnosis: Small brown Platyphyllini with tegmina barely covering abdomen and hairy legs ( Figs. 1 , 2A ). All genicular lobes armed. Male with pronotum posteriorly widened and disc with three white callose spots: one in the middle of anterior margin and two close together at rear margin ( Figs. 1A , 2D ), base of left tegmen opaque, right tegmen with transparent mirror. Female without white spots and considerably larger than male ( Fig. 1C ).

Additional descriptive notes: Fastigium short, scapi of antennae with prominent spine. Prosternum with fairly long spines. Male with a small whitish spot on tips of fore and middle femora and several indistinct spots on hind femora. Middle femora with 3 ventral spines in apical portion, hind femora with 4 small spines (5 in a female specimen with only one hind femur). Spines of inner genicular lobe of forefemur slightly larger than outer ones, contrariwise on hind femur. Male subgenital plate elongate, terminally emarginate, with long styli ( Fig. 2B ), male cerci with small sclerotized internal spinule ( Fig. 2C ). Ovipositor robust and slightly upcurved ( Figs. 1C , 2E ), female subgenital plate triangular with delicate terminal notch.

Measurements (male/female): pronotum 5.5/ 5–5.5 mm, tegmina 12/ 18 mm, hind femora 8/ 10 mm, male subgenital plate with styli 3.5 mm, ovipositor almost 10 mm.

Comparison with the two other species: The male holotype of M. festae is slightly larger and has a narrower pronotum, which is posteriorly hardly widened, with a slightly bilobed rear margen. It has only two white spots, widely separated on the corners of the rear margin (photos in Cigliano et al. 2021). The hind femora have 6 spinules ( Griffini 1896). The male of M. minutum is considerably smaller than the new species and has conspicuously long spines on the inner genicular lobes of the fore femora and the outer ones of the hind femora (about as long as dorsal width of the femora, Fig. 5 in Nickle 2006). The hind femora have 5–7 spinules (op. cit.). The male subgential plate has a very narrow terminal emargination (width and depth less than the width of the styli (op. cit. Fig. 26). Males of that species have a prominent trapezoidal whitish median spot on the frontal margin, and a very large one coating the entire metazona. In the holotype the frontal spot and the coated metazona are connected by a narrower whitish band, which is more weakly developed in the paratype (op. cit. Figs. 5, 24).

Calling song: The males produce at night extraordinarily long pulse trains of around 2 seconds (20°C, holotype in cage, Fig. 3A ) to over 3.5 seconds (13°C, field recording, Fig. 3E ). Independent of temperature they consist of around 15 pulse groups, each comprising 2–4 sustained pulses. The carrier frequency spectrum shows a very narrow peak just above 20 kHz and beyond human hearing range ( Fig. 3C ). The long pulses, almost pure sine waves, involve a slight frequency modulation ( Fig. 3D ). Probably sound is produced during closing strokes of the tegmina, with the low-amplitude signals preceding the pulses corresponding to the opening strokes ( Fig. 3B ).

Note to Braun 2002: The recording used for Fig. 6.3.3 “ Drepanoxiphus ?“ seems to have a technical issue: the redigitized copy shows a faint periodic background signal and the peak appears a little bit below 20 kHz, as in that figure. In the other recordings as well as the field recording it is above 20 kHz.

Figures

FIGURE 1. Mikrischyrum musicum: A. male holotype in dorsal view, B. same in lateral view, C. female paratype to same scale as B (specimen cbt019s01).

FIGURE 2. Mikrischyrum musicum: A. male habitus, B. male subgenital plate in ventral view, C. male left cercus in dorsal view, D. male pronotum in dorsal view, E. ovipositor of female (pencil drawings done in October 2003, after holotype and a paratype).

FIGURE 3. Calling song of Mikrischyrum musicum: A. oscillogram of complete pulse train (20°C, holotype, recording cbt- 019s04r03), B. first group of four pulses of A in higher resolution (and photo of holotype staged at day), C. linear spectrogram, D. zero-crossing analysis of one pulse, E. field recording together with two other katydid species, the arrow points at first pulse of the M. musicum sequence (13°C, cbt019x01r01, 14 August 1998), F. spectrogram taken from this recording with the distinctive peak of the new species, G. spectrogram of an unknown katydid species, showing the M. musicum peak too, H. spectrogram of an undescribed species of Aemasia (also Platyphyllini, song known from collected males, Braun 2002: Figs. 6.2.4, 6.3.3), based on the second call right after the end of the M. musicum sequence.