Bioacoustics of Parahabetia pictifrons

Comments. Ingrisch in revising Parahabetia , names these Bulolo Gorge specimens ( Ingrisch 2021 ) as a new subspecies of Parahabetia pictifrons . The name obtusa refers to the shape of the tips of the triangular rearward projections of the 10 th abdominal tergite: their bluntness distinguishes from P. p. acuta . In life the frons is a conspicuous blue green, as also the antennal scapes ( Fig. 59 ). Facial colours of this sort may be adaptive in concealing the insect from colour-vision predators such as birds: as the insect faces skyward legs extended, its coloured markings blend into the colours of bromeliad leaves used as a daytime refugium. The pronotum in dorsal aspect ( Fig. 61A ) shows conspicuously broadened lateral lobes (bullae) at the entry to the acoustic stigma, an adaptive acoustic feature. Stridulatory file. Male stridulatory file tiny ( Fig. 63 ), shortest distance between most proximal and distal tooth 1.2 mm , greatest width of teeth 0.075 mm ; of usual shape, slightly fusiform with proximal and distal parts curved and faintly sinuate in profile; total number of teeth 136 of which 89 are apparently functional and regularly spaced, 19 teeth per 0.25 mm . Stridulation. A resonant stridulation, judging by the simple ultrasonic high-Q sine wave at 34 kHz ( Figs 64C, D ). Also there is no suggestion of elastic uncoupling apparent in this single sustained pulse ( Fig. 64. B ). The insect repeats these 4-ms pulses at a regular period of just under 50 ms ( Fig. 64A ). Each call is comprised of>140 waves which the number of apparently functional teeth—89 (see above)—is inadequate to explain as a ‘one wave per file tooth event’. Something on the insect’s wing is oscillating making a simple wave train at one 34 kHz frequency. How is this possible unless more than one wave is associated with each tooth?

Description. Femora with the following number of spines on ventral margins: (1) a 7, p 9–10; (2) a 7, p 3; (3) missing (n=1). Male. Stridulatory file ( Fig. 22H ) 1,64 mm long, with 160 teeth, of which are 29 at curved base, 66 large around mid-length, and 65 after step, narrowing and becoming white towards end; area with largest teeth in middle of file with 84 teeth per 0,5 mm. Tenth abdominal tergite domed with faint medial furrow; apical area compressed, pointing posteriorly, and divided into a pair of acute lobes ( Fig. 21A ). Cercus curved mediad before second process and at end faintly laterad; with three dorso-internal projections: the basal projection consisting of a short stem and a compressed, disc-shaped apical area with a small spine at end; second projection narrow elongate with obtuse tip, followed shortly behind by an acute spine-like projection; cercus at end little widened and compressed but still swollen, with obliquely truncate end ( Figs 21B–C ). Subgenital plate at end only faintly incised, provided on both sides of incision and above insertion point of styli with a pair of narrow, slightly curved projections with little widened end ( Fig. 21D ). Titillators elongate and rather narrow; basal area slightly vaulted, curved laterad; central area elongate, nearly parallel-sided, not strongly sclerotized, with internal surface finely pubescent and rather soft; titillators at end strongly sclerotized, forming a hood carrying a compressed crest with little wavy margin that runs oblique against the surface of the apical area of the titillator ( Fig. 23D ). Measurements ( 1 male ).—Body w/o wings: 23; pronotum: 7; tegmen: 19.5 mm .

Diagnosis. P. p. acuta ssp. nov. differs from the nominate subspecies, P. p. pictifrons by the male tenth abdominal tergite that has the apical area divided into two long, narrowly spaced extensions with acute tip instead of more widely spaced obtuse extensions and the three internal projections of the male cerci differ in detail, e.g., the basal process has the tip disc-shaped with a spinule instead of simply little widened, the apical two projections are closer together and the tip is oval instead of rounded. From the subspecies P. p. obtusa ssp. nov. , the new subspecies differs by the apical extensions of the tenth abdominal tergite that run closer together, are straight and end into an acute tip instead of running more widely spaced, are downcurved and end into obtuse tips. The second and third internal projections of the male cerci stand closer together and the apical widening of the cercus is oval instead of globular. The male titillators are little narrower and less strongly curved in mid-length. The stridulatory file on the underside of the left tegmen is longer and carries more numerous teeth that are also in apical area clearly visible under a microscope. From both other subspecies, P. p. acuta also differs by the narrow apical extensions of the male subgenital plate that have the tip widened instead of narrowly rounded.

Description. Femora with the following number of spines on ventral margins: (1) a 6–7, p 8; (2) a 7–8, p 3–4; (3) a 10–12, p 12–20 (n=3). Male. Stridulatory file on underside of left tegmen 1.39 mm long with about 154 teeth: 25 teeth at curved base; 67 large teeth around mid-length; 62 teeth after step becoming white and indiscernible narrow toward end ( Fig. 22I ). Tenth abdominal tergite domed with medial furrow; apical area dorso-ventrally compressed and terminating into a pair of markedly spaced, elongate lobes with obtuse tip ( Fig. 21E ). Cerci elongate and narrow, curved around midlength, with three dorso-internal projections: the basal projection with a curved stem with globular end that carries a minute spinule, the second projection narrow, compressed and slightly curved, the third projection forming a short spine at base of the globularly swollen end of cercus ( Fig. 21F ). Subgenital plate above bases of styli with narrow projections that are longer than the styli and at end faintly out-curved ( Figs 21E, 21G ). Titillators with about basal half curved laterally and vaulted with convex distal and concave proximal surface, in roughly mid-length bent and apical half little widening towards end, at distal end swollen and with a lamellar crest at external side ( Figs 21E–G ). The lamellar crests are in situ the posterior ends of the titillators ( Fig. 23I ). Female. Subgenital plate in central and apical areas flattened and divided along mid-line by a furrow that is bordered on both sides by carinae that are, behind mid-length, deviating from each other, do not reach the end of the subgenital plate, and are connected by a thin septum that also forms the pair of obtuse apical lobes; both halves of the subgenital plate are standing angularly to each other and have the lateral areas occupied by a large oval swelling; central area and lateral swellings with smooth surface, a broad band along apical margin coarse ( Figs 24A, C ). Ovipositor upcurved, the ventral margin markedly stronger curved than the dorsal margin; dorsal margin in apical area slightly re-curved and faintly concave before acute tip ( Fig. 24B ). Measurements ( 2 males , 1 female ).—Body w/o wings: male 21.0–21.5, female 27; pronotum: male 6.3–6.5, female 6.2; tegmen: male 18.5–19.0, female 20.5; hind femur: male 14.5, female 14.5; ovipositor length: female 12.5 mm .

Diagnosis. P. p. obtusa ssp. nov. differs from the nominate subspecies, P. p. pictifrons , by the male tenth abdominal tergite that has the apical area divided into two long triangular extensions instead of short lobes and the three internal projections of the male cerci differ in detail as shown in Figs 21E–F compared to Fig. 21H : the first projection inserts closer to the base of the cercus but farther away from the second process and the apical swelling of the cercus is smaller. From the subspecies P. p. acuta ssp. nov. , the new subspecies differs by the apical projections of the tenth abdominal tergite that are at end little downcurved and with obtuse tip instead of being sub-straight and with acute tip. The male cerci differ in detail between both subspecies as shown in Fig. 21F compared to Fig. 21C . The stridulatory file on the underside of the left tegmen in P. p. obtusa is shorter than in P. p. acuta with less numerous teeth. The male titillators are similar in both subspecies but more strongly curved between basal and apical area in P. p. obtusa and the apical area is wider than in P. p. acuta .