Hypoponera zwaluwenburgi
Hypoponera zwaluwenburgi is a small (2–2.3 mm) brownish yellow species with short antennal scapes, no eyes, a short subtriangular petiole, and a strongly reduced subpetiolar process. The species was originally described from eleven specimens taken by Mr. R. H. Van Zwaluwenburg at Waimalo, Waialua, and Waipio on Oahu Island, and also on Maui Island (Wheeler, 1933b). They were collected from below the surface in the soil of both cultivated and fallow sugar-cane fields. Despite the multiple distributions reported from the original description, and the apparently large amount of suitable habitat, the species has not been collected in Hawaii since 1967 (Krushelnycky et al., 2005). The only other record of the species is from Okinawa, Japan (Imai et al., 2003).
Not considered a significant pest species.
Diagnosis of worker among Antkey species. Antenna 12-segmented. Antennal scapes do not reach posterior head margin. Eyes absent (0 facets). Frontal lobes relatively narrow. Clypeus with anterior margin flat to convex, but never forming a distinct triangle that projects anteriorly beyond the base of the mandibles. Mandibles triangular; with more than 7 teeth and denticles. Metanotum does not form a prominent convexity bordered by distinct suture lines. Hind coxae lacking dorsal spine. Hind tibia with pectinate spur, but without simple spur. Tarsal claws lacking subapical tooth. Waist 1-segmented. Petiole subtriangular, relatively short and broad with distinctly convex anterior and posterior faces and a strongly reduced subpetiolar process; narrowly attached to gaster; conspicuous posterior face. Gaster armed with sting. Distinct constriction between abdominal segments 3+4. Abdominal segment 4 lacking deep longitudinal furrows. Color brownish yellow. Sculpture mostly shining.
Hypoponera zwaluwenburgi is a rather aberrant member of the genus with its complete lack of eyes, strongly reduced subpetiolar process, and the presence of an epimeral sclerite in the males (Bolton & Fisher, 2011; Imai et al., 2003; Wilson, 1957), and in general is highly convergent with Ponera (Taylor, 1967). Among Antkey species, H. zwaluwenburgi can be separated from its congeners by the absence of the eyes, the strongly reduced subpetiolar process, and the shorter and more triangular petiole. It can be separated from Ponera swezeyi by the subpetiolar process, which lacks a fenestra and a posteriorly pointing tooth, and also by the lack of eyes.
Native range vs. introduced range unknown. Hawaii: Oahu I. (Waimalo, Waialua, and Waipio), Maui I. Japan: Okinawa.