Diacamma rugosum jerdoni Forel, 1903

Baidwan, Parvinder Singh, Kapoor, Rakeshwar & Bharti, Harmanbir Kaur Randhawa And Himender, 2024, Description of Diacamma rugosum jerdoni (Insecta: Hymenoptera) male with two new additions to the myrmecofaunal diversity of Kerala, Halteres 14, pp. 20-30 : 24-26

Diacamma rugosum jerdoni Forel, 1903 ( Figs 2-4)

Diacamma rugosum jerdoni Forel, 1903c: 401 . Type locality: Sri Lanka [Ceylon] [Syntype: MHNG]. [Images of CASENT 0907222 syntype worker examined].

Redescription (Worker) ( Fig. 2)

Workers measurements: TL 12.0-12.5; HW 2.17-2.21; HL 2.58-2.62; SL 2.87; WL 3.56-3.64; MTL 2.05- 2.09; PH 1.43-1.47; PL 1.02-1.06; PW 1.23; SpD 0.48-0.57; SpL 0.28; EL 0.60-0.61; EW 0.41-0.43 (n=2). Indices: CI 84.10-84.35; SI 129.86-132.20; PI 69.38-74.12; SpDI 39.02-46.34; SpLI 22.76; EI 27.60-27.64. Description: Head distinctly longer than broad (HL 2.58- 2.62; HW 2.17- 2.21); head oval in shape, occipital corners rounded, lateral sides convex; clypeus broad and convex, anterior clypeal margin with rounded lobe; eyes large slightly longer than wide (EL 0.60-0.61; EW 0.41-0.43), convex; mandibles triangular, masticatory margin with 7-teeth; antennae 12-segmented, scapes extending beyond the top of the head by one-third of its length; pedicle short.

In dorsal view, mesosoma broad anteriorly and narrow posteriorly; pro-mesonotal suture and metanotal groove distinct; pronotum broader than mesonotum and propodeum; mesonotum reduced, broader than long; propodeum longer than broad; propodeal declivity steep; petiolar node broader than long (PW 1.23; PL 1.02-1.06); dorsal surface of petiolar node armed with a pair of acute spines; gaster cylindrical.

In lateral view, mesosoma do not form a single convexity; propodeal declivity convex and continuous with dorsal surface of propodeum; petiole rectangular in profile, anterodorsal margin convex, posteriodorsal margin truncated; node higher and broader than long ( PH 1.43-1.47; PW 1.23; PL 1.02-1.06); gaster cylindrical, curved posteriorly, dorsal convex; gaster longer than mesosoma; sting long and curved upward. Dorsal surface of head longitudinally striated; clypeus and frontal area opaque and densely punctated; mandibles finely longitudinally striated; dorsal surface of pronotum with longitudinal concentrical and circular rugae; laterally mesosoma obliquely striated; dorsal surface of propodeal declivity transversely striated; petiolar node with concentric striations; first gastral tergite with transverse concentric striations and rest of gastral segments smooth and shiny.

Pilosity and pubescence: Whole body surface covered with dense erect and sub-erect hairs; appressed pubescence dense all over the body surface.

Body blackish in colour; mandibles, antennae and appendages dark brownish in colour.

Description (Male) ( Fig. 3)

Male measurements: HL 0.96; HW 1.44; ML: 0.15; CW 0.69; CL 0.43; SL 0.34; EL 0.76; EW 0.43; WL 3.48; PH 0.88; PL 1.03; GL 4.40; PFL 1.94; PFW 0.26; MFL 1.3; MTL 2.29; HFL 2.46; HTL 2.29; PnW 1.72; PW 0.84; TL 10.02mm (n=1).

Indices: CI 150; MI 10; OI 52; SI 23; LPI 85; DPI 81.

Description: Body smaller than the workers; head in full-face view much broader than long (HL 0.96; HW 1.44;) including compound eye with roundly convex posterior margin; clypeus rectangular wider than long (CW 0.69; CL0.43); mandible reduced, feeble with apex rounded; eye large and elongated (EL 0.76; EW 0.43), with head in dorsal view bulging, breaking lateral (outer) margin of head; three ocelli large and very prominent; antennae 13- segmented; scape short, slightly wider and 1/3 shorter than flagellomere 1; pedicel slightly shorter than 1/2 of length of scape; flagellomeres long, narrow and cylindrical; pronotum with short dorsal plane, anteriorly convex, lateral face large, smooth shiny; mesoscutum large, almost as long as wide, with strongly convex anterior margin, mesoscutum separated from mesoscutellum by scutoscutellar sulcus; postscutellum and metanotum depressed; metanotal disc small, posteriorly narrow, well-demarcated from mesoscutellum by deep groove; metapleuron divided into upper and lower areas by shallow furrow; propodeum distinguished from metapleuron by shallow sulci, in dorsal view slightly longer than broad, spiracle located close to metapleuron; petiole nodiform, in lateral view ( PH 0.88; PL 1.03) longer than high, in dorsal longer than broad, spine and denticulation absent; in dorsal view gastral segment I longer and narrow than segment II; legs somewhat long in proportion to mesosoma, femora longer than tibiae; mesoand meta-tibiae each with two apicoventral spurs; claws with small denticle apically.

Head smooth, generally shiny and never striate; clypeus coriarious-punctate; antennal scape and pedicel superficially rugulose; mesosoma striate and shiny; mesoscutellum and narrow median section of metapleuron shiny; scutoscutellar sulcus smooth; propodeum smooth; petiolar node smooth and shiny with superficial striations around apex. Gaster is smooth and shiny; coxae micro reticulated and less shiny.

Femora, tibiae and tarsi with dense short suberect hair; dorsum of the head densely covered with short suberect hairs; hairs sparsely present around ocelli; mandible basally and apically with suberect hairs; clypeus basally with short suberect hairs and apically with long erect hairs; pedicel and flagellum densely covered with short pubescence; mesosoma and petiole covered with short pubescence and suberect or erect hairs; legs almost completely covered with appressed pubescence; gastral tergites and sternites with pubescence and sparsely longer hairs that are slightly denser at posterior gastral sternite.

The entire body light yellowish brown; areas around the ocelli are slightly darker; tibiae and tarsi darker than coxae and femora.

Material examined: INDIA, Kerala, Chimmony Wildlife Sanctuary , 10.44083 N 76.53527 E, 83m, Hand picking, 14-1-2023, 2w, 1m, Rakeshwar Kapoor leg. ( PUAC).

Natural History notes

The nests of Diacamma rugosum jerdoni were predominantly located beneath stones. When the stone covering a nest was turned, the nest became exposed, prompting a swift and organized response from the ants. A subset of workers immediately began searching for potential invaders, while the remainder focused on relocating the broods to deeper, more secure areas within the nest. Additionally, a male ant, which had started to move away, was quickly captured by the workers and transported to a safer location deeper in the nest ( Fig. 4).