Plangia graminea Serville 1838

Plangia graminea (Serville, 1838)

http://lsid.speciesfile.org/urn:lsid: Orthoptera.speciesfile.org:TaxonName:9853

(Figs. 5G, 44 F–L, 53G–I)

Diagnostic remarks. A medium size, fully-winged katydid (Fig. 44G) that can be distinguished from members of the genus Eurycorypha by the shape of the compound eyes, which are nearly globular rather than oval and show a distinct pattern of vertical stripes. The fastigium of vertex is also narrower than in Eurycorypha spp. albeit usually wider than the scapus. P. graminea can be identified among its congeners by the shape of male cerci (Fig. 44F), which are slightly sinuous and evenly tapered towards the apex.

Bioacoustics. The call of P. graminea consists a series of echemes made up of two closely spaced syllables produced every 3–5 s; mean syllable duration is 0.048 s (SD=0.0040, n=20); the peak frequency of the call is 9.9–11.7 kHz (Figs. 53 G–I). The call is audible from a distance of a few meters.

Distribution and natural history. The identity, and thus distribution and biology of P. graminea, had been uncertain for a long time due to the loss of its holotype until the recent designation of the neotype by Hemp (2017b). Specimens that agree with the neotype in the morphology of the male external genitalia and stridulatory file have been collected across South Africa and central Mozambique, but records from Zambia and W Africa (Ragge 1968b) should be treated with caution.

P. graminea is considered a minor pest of vineyards in South Africa (Bazelet 2013), where it is known locally as “krompokkel. Both nymphs and adults feed on young shoots and leaves of the grape wine but cause relatively little damage.

Females have a robust ovipositor adapted to laying eggs inside stems of plants (Fig. 44J); eggs are laid in clusters of 3–5. Young nymphs of this species are dramatically different from the adults and appear to mimic toxic leaf beetles (Chrysomelidae). They have black coloration, punctuated with bright yellow spots on the knees and head (Fig. 44K) that from a distance can be confused with droplets of yellow hemolymph that some toxic leaf beetles are known to produce. At this stage, during instars 1–3, the nymphs are diurnal but older instars begin to resemble typical green katydid nymphs (Fig. 44L) and become nocturnal.

Measurements (2 males, 3 females). body w/wings: male 47.5, female 44–48.5 (45.52.6); body w/o wings: male 25.3–27.2 (26.31.3), female 24–32.2 (27.14.5); pronotum: male 6.8–7 (6.9.1), female 7–7.1 (7.1); tegmen: male 36.5–37.1 (36.8.4), female 36–37.9 (36.61.1); hind femur: male 17.7, female 17–19.3 (18.11.2); ovipositor: 6.6–7 (6.9.2) mm.

Material examined (8 specimens). Mozambique: Manica, Sussundenga, Moribane Forest, Ndzou Camp, elev. 593 m (-19.734695, 33.336130), 2–8.xii.2018, coll. P. Naskrecki & M. Tomás— 1 male; Sofala, Cheringoma, nr. Codzo (Khodzue), cave and nearby, elev. 216 m (-18.564, 34.872222), 14–25.iv.2017, coll. P. Naskrecki— 1 female (EOWL); Gorongosa, GNP, Bunga Inselberg, Camp 1, nr. Bunga ranger outpost, elev. 75 m (-18.59989, 34.33686), 21.iv.–5.v.2015, coll. P. Naskrecki— 1 female; Gorongosa Dist., Center for Environmental Conservation, elev. 119 m (-18.95472, 34.1775), 16.iii.2013, coll. P. Naskrecki—1 nymph (MCZ); Wilson Laboratory, GNP, Chitengo, (-18.97775, 34.351333), 19.iii.–2.iv.2014, coll. P. Naskrecki & R. Guta— 1 female; same locality, 19–28.ii.2017, coll. P. Naskrecki— 2 males (EOWL); GNP, Chitengo, elev. 29 m (-18.98194, 34.35122), 6–31.v.2013, coll. P. Naskrecki— 1 female (MCZ).