Acanthocasuarina Taylor
Creators: name: Taylor, Gary S.
name: Jennings, John T.
name: Purcell, Matthew F.
name: Austin, Andy D.
Publisher: name: Zenodo
Year: 2011
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Hemiptera
Triozidae
Acanthocasuarina

description: Acanthocasuarina Taylor, gen. nov.
Type species: Acanthocasuarina acutivalvis sp. nov.
Description. Adult. General colour pale ochraceous to orange-brown with brown to black markings; vertex pale with brown marking in vicinity of fovea; genal processes with brown to black infuscation at apices; antennal segments 1–2 brown to black; segments 3–10 antennal ochraceous to brown, progressively dark brown to black towards apex; pronotum, mesonotum, mesopraescutum and metascutum pale ochraceous to orange-brown with pale orange-brown to dark brown markings; fore wings clear; abdominal tergites brown to dark brown; male terminalia pale ochraceous to orange-brown; female terminalia pale ochraceous to orange-brown with brown to black markings.
Structure: Antennae short, 0.6–0.9 mm in length, 1.1–1.7 times width of head, 10-segmented, a single subapical rhinarium on each of segments 4, 6, 8 and 9; segment 3 short, 0.16–0.26 mm; segment 10 with 1 long, pointed and 1 short, truncate apical setae; genal processes thin, elongate with rounded apices 0.10–0.20 mm long, about 0.5–0.9 times length of vertex, divergent, little declined about 40° to longitudinal axis of vertex and about 70° to longitudinal axis of body; anterior margin of vertex delineated by moderate ridge, overhanging median ocellus and genal processes; vertex short, broad, 0.5–0.8 times longer than wide with prominent medial suture and prominent fovea; occipital margin sharply defined; head wider than pronotum and mesoscutum; pronotum short, broad with prominent anterior, medial node; thorax rather flat dorsally; fore wings clear, elongate-oval, 2.7–3.4 times longer than wide with broadly rounded apex; Rs short, terminating well short of wing apex; vein m1+2 terminating little anterior of wing apex; M branch on or distal to Rs-Cu1a line; cell m1 short, broad (m1 cell value 0.8–1.4); cell cu1 short to moderately long (cu1 cell value 0.7–2.3); radular areas elongate triangular at margin of wing in cells m1, m2 and cu1; meracanthus conical, pointed; apical hind tibia with 1 outer and 2 inner spurs; basitarsi without spurs; hind tibia with basal genual node. Male proctiger unipartite, short, without lateral expansions; subgenital plate of male short, rounded; parameres thin, elongate, strongly curved inward towards apex to short with rounded posterior lobe. Female proctiger short, 0.33–0.51 mm in length, 0.5–0.9 times width of head, broadly rounded, with prominent apical hook, ovipositor long, thin and either straight or curved upward, subgenital plate short, narrow, broadly rounded, triangular from lateral aspect.
Nymph (Figs 74, 82–83, 92, 110, 126) elongate-narrow, moderately to weakly sclerotised, scale-like; body about 1.80–1.90 times longer than wide; antennae short; cephalothorax entire, usually with a single depression on each of meso- and metathoracic tergites; fore wing pads produced anteriorly, confluent with lateral margin of head; abdominal tergites fused to form caudal plate; caudal plate elongate, narrow, about 1.0–1.2 times longer than wide; circum-anal pore field ventral and distant from posterior margin of abdomen; sectasetae short, truncate on margins of head, fore and hind wing margins, and margins of caudal plate; dorsum without sectasetae.
Diagnosis. Species of Acanthocasuarina can be distinguished from all other triozids by the following combination of characters: antennae short, 1.0–1.7 times width of head, with single rhinarium present subapically on segments 4, 6, 8 and 9, genal processes moderately long, conical, 0.5–0.9 times length of vertex, produced ventrally and delineated from vertex by a prominent overhanging ridge, apex of fore wings broadly rounded, wings clear, vein Rs short, medial cell short, broad, and cubital cell short, broad to moderately elongate, hind tibia with 1 outer and 2 inner spurs, male proctiger short, without lateral expansions, parameres simple, female proctiger short, with a prominent apical upturned process or hook, nymphs elongate-narrow, moderately sclerotised and scale-like. It differs from Aacanthocnema in the arrangement of antennal rhinaria (on segments 4, 6, 8 and 9 in Acanthocasuarina, absent on segment 8 in Aacanthocnema), status of spurs on apical hind tibia (present in Acanthocasuarina, absent in Aacanthocnema), shape of the female proctiger (with an apical hook in Acanthocasuarina, without in Aacanthocnema) and shape of the ovipositor (long, thin and either straight or curved upward in Acanthocasuarina, short, stout and straight in Acacanthocnema).
Etymology. From acantho (Greek), spine, refers to the presence of spurs on the hind tibia + casuarina, the colloquial name s.l. for the host.
Comments. Acanthocasuarina is the sister taxon to Aacanthocnema and can be clearly separated by the above-mentioned suite of characters. The two genera can be separated from all other triozids from the Casuarinaceae by the following suite of characters: elongate habitus, short Rs vein, and short, triangular radial and cubital fore wing cells, ventrally produced genal processes beneath angular, overhanging apical margin of vertex; short antennae; short broadly-rounded female terminalia, and nymphs elongate, scale-like, with very short, blunt peripheral sectasetae. Being scale-like, the nymphs are clearly adapted to an arid environment, and their elongate habitus and concave ventrum adapted to living on the narrowly cylindrical ‘foliage’ of their host.
Acanthocasuarina differs from Casuarinicola, and undescribed species of Casuarinaceae-inhabiting Trioza which all have a shorter habitus, with body generally angled upward from the substrate when at rest, short, conical genal processes, and nymphs that are broadly ovate (when slide mounted, although curved around the elongate ‘foliage’ when live). It is distinct from an additional suite of undescribed species from the Casuarinaceae in which the antennae are long, the radial and cubital cells of the fore wings are elongate triangular, the genal processes are elongate and produced forward in the same plane as the vertex, and with female terminalia that are generally, some considerably, more elongate.
description: Published as part of Taylor, Gary S., Jennings, John T., Purcell, Matthew F. & Austin, Andy D., 2011, A new genus and ten new species of jumping plant lice (Hemiptera: Triozidae) from Allocasuarina (Casuarinaceae) in Australia, pp. 1-45 in Zootaxa 3009 on pages 27-28, DOI: 10.5281/zenodo.278552