Dendrobia plagata, Hemp & Heller, 2019

Hemp, Claudia & Heller, Klaus-Gerhard, 2019, New Agraeciini species from the Eastern Arc Mountains, East Africa (Orthoptera: Tettigoniidae; Conocephalinae; Agraeciini), Zootaxa 4664 (3), pp. 301-338 : 327-332

Dendrobia plagata n. sp. Hemp C.

( Figs. 35–38 , 41 , 42 , Table 1 )

Holotype: male. Tanzania, Nguru Mountains , montane forest, March 2019. 5 females, same data as holotype but February 2017, March 2017 and July 2017. Depository: collection C. Hemp.

Description. Male. Habitus and colour. Plump medium-sized insect, predominantly leaf green with brown-red- dish broad fascia on margins where tegmina meet medially. Remaining part of tegmina with net-like pattern of dark green veins on light green ground. Pronotum with 6 longish dark dots on cream coloured ground arranged in pairs ( Fig. 35 A, C ). Eyes light. Head and antennae. Face broad, predominantly of whitish to green colour. Antennae cream coloured with scapus and first antennal segment green. Fore and mid femora with 4 stout spines ventro-an- teriorly, white, with black tips. Hind femora with 8 broad-based spines ventro-anteriorly along whole length and 4 stout spines near joints to tibiae ventro-posteriorly. Stridulatory file with about 150 teeth on 3.2 mm, in the middle tooth interval 22 µm (45 teeth/mm). Abdomen. Last abdominal tergite broad with almost straight posterior margin with a median depression. Cerci vertically flattened, with a blunt outer branch and an inner branch with up-lifted sclerotized tip ( Fig. 36 B ). Subgenital plate broad, posterior margin v-shaped incised, with thin styli.

Female. Similar in habitus and colour as male with same spination. Ovipositor long, slightly up-curved with smooth sclerotized valves ( Fig. 35 B, D ). Subgenital plate with median rectangular incision on posterior margin and lateral edges since sheathing central knob-like structure ( Fig. 37 C, D ).

Nymph. Similar to adult, L4 nymphs were successfully reared to adults ( Fig. 38 ).

Measurements, males (mm) (N=1). Total length of body (including cerci): 27; median length of pronotum 15; length of hind femur 15.5; length of tegmina 20.

Measurements, females (mm) (N=4). Total length of body 24.6–30.2; Median length of pronotum 11.2–12.1; Length of hind femur 16.5–17.7; Length of elytra 21.2–23.2; Length of ovipositor 14.1–16.8.

Song. As in the other species of Dendrobia , the male sang very rarely. The song was clearly audible with the human ear. It produced often only one group of echemes per day (continously monitored). These sounds were registered in the late afternoon or in the morning. The echemes had a mean duration of 1.4 s, distinctly longer than in the other two species (see Fig. 41 ) and period of 2.2 seconds (n=5/7) with a SRR of about 19 Hz. The peak of the carrier frequency was with about 7 kHz even slightly lower than in the other Dendrobia species. See Fig. 41 , 42 and Table 1 for details.

Diagnosis. D. plagata n. sp. is characterized by its net-like pattern on the tegmina, both in the male and the known females compared to D. amaniensis Hemp & Ingrisch, 2017 from the East Usambara Mountains and D. octopunctata Hemp, 2017 from the Udzungwa Mountains being of more uniform green colour. The median reddish stripe is more conspicuous red and broad in D. plagata n. sp. compared to the other two species. The male cerci are vertically flattened and thus very different from the bulbous cerci of D. octopunctata ( Fig. 36 C ) but similar to the genitalic apparatus found in D. amaniensis ( Fig. 36 A ). The latter species also has vertically flattened male cerci but the branches are differently shaped (compare Fig 36 A and B ). D. plagata n. sp. has an inner branch of the male cerci up-lifted while the male cerci in D. amaniensis are more flattened and shovel-like expanded but the inner tips of the cerci are not or only very slightly up-lifted.

The females of all three known species have a similar subgenital plate with a central knob-like structure on the ovipositor sheathed by the subgenital plate ( Fig. 37 A–D). Differences are found in the size of the median incision and the lateral processes caused by the central knob-like structure. However, females are best identified with associate males and their area of occurrence since all three species are restricted to single mountain ranges of the Eastern Arc chain.

Biology. Dweller of the tree canopy. Probably predaceous, in captivity feeding on fruit, cereals and insect parts.

Habitat. Submontane to montane forest.

Distribution. Tanzania, Nguru Mountains.

Etymology. From Latin:— plaga, net because of the net-like pattern on the tegmina.

Figures

FIGURE 35. Dendrobia plagata n. sp. A. Male, habitus B. Female, habitus C. Male, lateral view on pronotum with typical pattern D. Female, dorsal view.

FIGURE 36. Apices of alive male Dendrobia species A. D. amaniensis B. D. plagata n. sp. C. D. octopunctata.

FIGURE 37. Subgenital plates of female Dendrobia species. A. D. amaniensis B. D. octopunctata C, D. D. plagata preserved (C) and alive (D). Arrows point to a knob-like structure at the base of the ovipositor sheathed by the subgenital plate.

FIGURE 38. Fourth instar of female Dendrobia plagata n. sp.

FIGURE 41. Oscillograms of the calling song of all known Dendrobia species.

FIGURE 42. Power spectra of the calling song of Afroanthracites, Afroagraecia and Dendrobia species. In A. guttatus the restricted frequency range is marked by a black line at its end.