Bioacoustics of Meconema thalassinum

The remarkable nocturanl 'song' of this insect is not produced by stridulation but by a rapid drumming of one of the hind legs on teh substrate. It is clearly intended for conduction through the substrate and so the airborne sound produced is incidental and very quiet. To produce the sound the male raises both pairs of wings more or less perpendicularly to the body and vibrates one of the hind legs so the that its tarsus is drummed on the surface of the leaf, twig or any other substrate that the male happens to be using. The drumming is in short bursts of up to a second or slightly longerand these are almost always in sequences of up to seven bursts, separated from other such sequences by intervals of at least several seconds (3-15 s in the songs studied). Each sequence is usally composed of a combination of shorter and longer bursts, with the shorter ones preceeding the longer ones. Each shorter burst usually consists of 3-8 impacts and lasts for about 0.07-0.20s, while each longer one usually consists of 30-50 impacts and lasts for about 0.7-1.3s. The impact repetiton rate, in both shorter and longer bursts, is usually 3-40/s at temperatures up to 25°C, but can be as much as 60/s or more at higher temperatures. The number of short and long bursts in a sequence is very variable: 2-3 short ones followed by 1 or 2 long ones is a common patterm, but there can be as many as 5 of either kind (though not in the same sequence) and some sequences lack short bursts completeky. The interval between successive bursts lasts about 0.2-2.0s. The quality of the airborne sound depends on the substrate. Drumming on a twig is extremely faint, but if a suitable leaf is used the sound can sometimes be heard from a distance of several metres.

Figures 67 (lateral), 68 (dorsal, ventral) Plates 43 (lateral), 44 (dorsal, ventral) The female drumming katydid we scanned is likely a late-stage instar due to the reduced wings. T2-DB-Vi and T3-DB-Vi each form a trapezoidal set of double dorsal commissures. It is possible that these may be homologous with sausagelike dorsal commissures seen in other taxa that might be for weight relief or could be involved in stridulatory sound dissemination. DESCRIPTION: HEAD: Three pairs of tracheae into head: H-DCT, H-VCT, and H-VLT. Head with several interconnected dorsoventral and lateral loops; readers are encouraged to review the supplementary 3D digital models. Air space, possibly a preservational artifact, present in right side of head capsule (see fig. 69 ). H-DCT runs anteriad, curving dorsally along head capsule and curving medially to connect in a loop just dorsal of eyes. H-DC present. Anteriad of cervix, H-DCT-Oc branches ventrad, linking with H-VCT-Oc with Y-shaped junction to H-Oc-Md. Several small, visceralike H-Oc run dorsad from H-Oc-Md; H-Oc-Md anteriad, reconnecting to H-VCT with H-Md branching anteriad, with lateral H-FtC branch linking left and right side. H-VCT runs anteriad with ventral curve; T1-AL running posteriad prior to H-VCT entry to head capsule. H-VCT with aforementioned H-VCT-Oc branch running anteriad; H-VCT continuing anteriad with ventral branch, linking with H-VLT before continuing into H-Mx and H-Lbm split. THORAX: T2-S opening very large, positioned under pronotum; T2-S with five branches: T2-DB, T2-VB, H-DCT, H-VCT, and T1-PL. Several tracheae behind T1-DVi; see figure 70 for view rotated to see additional detail. Readers are also directed to 3D models from supplemental digital data. T2-DB and T2-VB from short dorsal spiracular branch, extending directly dorsad and ventrad, respectively. T2-DB with T2-AWL split, with T2-DB continuing dorsad, connecting with T2-DLT extending posteriorly. T2-AWL runs dorsad with sharp curve directly ventrad toward midleg; T2-W-c-r positioned posteriad at apex of curve. T2-VB runs directly ventrad from T2-DB/T2-VB split, arcing posteriad to connect with T2-VLT; several small visceral branches forming cagelike network along venter. H-DCT runs dorsad from T2-S, arcing anteriad and continuing through prothorax into head capsule; T1-DVi branches forming cagelike morphology along inner wall of protergum, around H-DCT. H-VCT runs dorsad, arcing ventrad before turning anteriad into head capsule, arranged along outside of enlarged T1-PL; T1-AL with ventral branch anteriad of T1-PL. T1-PL greatly enlarged in hornlike arc, reducing in size and extending into proleg. T1-L-Ty tympanum present on foreleg tibia. T3-S much smaller than T2-S, with five branches: T3-DB, T2-PWL, T3-AWL, T3-VB, and T2-PL. T3-DB and T3-VB split dorsad and ventrad after short dorsal spiracular branch from T3-S. T3-DB running directly dorsad, with T3-AWL branching dorsad and slightly lateral; T3-DB continuing dorsad to join with T2-DLT from anterior and smaller T3-DLT posteriad. T3-AWL runs dorsad, with sharp curve ventrad and posteriad toward midleg. T3-AWL with two connections to tracheae leading to A1-S: T3-Wbr, branching dorsally at apex of curve, with T3-W-c-r and T3-W-cu-a dorsad; and apparent T3-PWL extension, dorsal and anteriad from A1-S, connecting with T3-AWL/T3-AL. (See Discussion on Orthoptera .) T3-VB runs mediad and ventrad, connecting with T3-VLT toward posterior and T2-VLT anteriad. T2-PL ventrad with curving T2-pf branch to T2-VLT; T2-PL continues into midleg, joining with T2-AL. ABDOMEN: A1..8-S present. A1-S modified, positioned slightly dorsad relative to A2..8-S. A1-S with four connections: A1-DB, T3-PWL, A1-VB, and T3-PL. Single A1-DB runs dorsad and slightly anterior, broad and flat; intersecting with T3-DLT anteriad and A1-DLT posteriad. Several small visceral-type tracheae connecting with T3-PWL and and likely extending into flight musculature. T3-PWL running dorsad and anteriad, similar to A1-DB but smaller; T3-PWL splitting slightly dorsad into T3-Wbr anteriad connection to T3-S, and smaller unnamed extension connecting to T3-AL (see THORAX, above, and Discussion section on Orthoptera ). T3-PL thick, running directly ventrad from A1-S, connecting with smaller T3-AL from metathorax and extending into hind leg. T3-VL present, extending into hind leg from T3-VLT. A1-VB runs ventrad and slightly mediad, connecting with T3-VLT from anterior and A1-VLT posteriad. A2..8-S similar, each with anterior and posterior dorsal branches A n -ADB and A n -PDB, both intersecting with A n -DLT along dorsum. A n -VB short, running ventrad and slightly mediad, connecting directly to A n -VLT along venter. X-shaped commissures positioned ventrad to VLT (see fig. 71 ). Numerous visceral tracheae present in abdomen, often spanning several segments, but none appearing to connect segments longitudinally.