Tachycixius chaoensis

Tachycixius chaoensis (China, 1938) comb. nov.

Figs 3E, 5F, 6B, D, 8E–F, 10A–M

Cixius chaoensis China, 1938: 51–52, fig. 22 (description, illustrations, records).

Cixius chaoensis – Lindberg 1961: 55 (records).

Diagnosis

Tachycixius chaoensis differs from species of the same genus in the form of aedeagus: (1) the velum has a narrow, hump-shaped expansion at the base, and the apical part is arched and thinner than at base; the apex forks into a straight spine-like dorsal projection and a larger scythe-shaped ventral expansion sharply bent to the left; (2) on each side, the basal part of the aedeagus has two small and thin spines strongly curved inward. There are four endemic species of Tachycixius in the Canary Islands grouped in the T. canariensis group (Holzinger 2000). Tachycixius chaoensis differs from them in: (1) the vellum which has a hump-shaped expansion and the apex is bifurcated, not blunt; (2) the movable spines are of similar size and are on each side of the theca, and strongly curved inward; they are also smaller and thinner than in the Canarian species; (3) the medioventral expansion of the theca has a wave-crested shape, and the proximal end is concave and ends in a solid, thin and inwardly curved ventral spine.

Material examined

Lectotype (here designated) (Fig. 6B, D)

MADEIRA ISLANDS – Desertas Islands, Ilhéu Chão • ♂ (glued on a card with 1 st left tibia and tarsi glued separately (Fig. 6B, D) and abdomen dissected (in a separated dissection slide), bearing seven labels); a black rectangular label (handwritten) reading “ Cixius / châoensis /TYPE China/ [printed] det. W.E.China.1937 ”; a white round label with red printed circle, in the center of this with black printed letters written “Type”; a small rectangular label printed “♂”; three black typed printed labels reading “Madeira./Wollaston./B.M.1855-7.”; “N.Dezerta/Ilheo Châo”; “DISSECTIONS/IN SLIDE/ COLLECTION.”; a rectangular label with QR symbol and reading “NHMUK 010748310”; NHMUK 010748310.

Paralectotypes

MADEIRA ISLANDS – Desertas Islands, Ilhéu Chão • 5 ♂♂, 2 ♀♀; “Habitat: Northern Dezerta, (Ilheo Chão)”, each labelled “ paratype ”; NHMUK.

Other material

MADEIRA ISLANDS – Machico • 2 ♂♂, 3 ♀♀; Ponta de São Lourenço; 50 m a.s.l.; 11 May 2001; Sara Machado leg.; on Suaeda vera; UMACI.

Redescription

BODY MEASUREMENTS (mm). See Table 1.

COLOURATION. Males overall colouration light brown, females darker (Fig. 3E). Vertex brown with two paler oval spots at the level of anterior margin of eyes; areolar carina dark brown. Frons and medial ocellus yellowish-brown in males and darker in females. Postclypeus yellowish medially with outer margins darker. Anteclypeus brown, slightly lighter medially; in females, the clypeus is darker. Genae, lora and 2 nd antennal segment dark brown. Lateral ocelli golden brown. Eyes blackish brown. Pronotum amber yellow, often light brown medially behind vertex and at posterior angles. Mesonotum brown or dark brown, in some specimens the carinae and posterior margin lighter. Tegula pale brown to light brown. Tegmina translucent, whitish; longitudinal veins pale (Figs 3E, 5F). Some specimens have a darker obliquus strip at ⅓ of the base. Stigma is whitish to dark brown. Wing markings in males reduced and the strips lighter or unnoticeable; legs light brown to brown with varying degrees of shade. Colouration of the abdomen in males and females as in C. madeirensis.

HEAD. Vertex anteriorly tongue-shaped and concave, and posteriorly trapeze-shaped (Fig. 10B); medially short, about ¾ times as long as wide at the level of anterior eyes margin. Medial carina of the frons smooth, reaching the posterior margin of postclypeus (Fig. 10A). Epistomal suture parabola-shaped, the height of the crest-wave about ⅓ of its width at the base. Lateral pits between the vertex and forehead shallow. Medial ocellus reduced or obsolete.

THORAX. Pronotum and carinae as in C. madeirensis (Fig. 10B). Lateral carinae of mesonotum 2 times more separated distally than basally; length of medial carina about ⅔ of the mesonotum length; the distal area between lateral carinae slightly concave. Tegmina short, narrowing to its distal end; 2.5 times as long as wide in its widest part (Fig. 5F); in females the tegmina are slightly shorter than the abdomen length; bristles along veins sporadic. Metatibia with 3 small lateral spines; 1 st spine located near tibiofemoral joints; the other two spines separated from each other by about ¼ of the tibia length. First metatarsus with 6 spines distally.

MALE GENITALIA. Pygofer lobes form an elongated parabola (Fig. 10H). Anal tube asymmetric ventrocaudally, with the caudal margin slightly concave laterally (Fig. 10E); lateral distal lobes thumblike with apex roundish; they bend ventrally with the distal part wider than at the base. Anal style globular, pear-shaped as the cactus fruit (Fig. 10F). Paramere tongue-shaped distally; lamella higher than wide at the base with ventral margin convex and proximal margin slightly oblique (Fig. 10G). Right ventral margin of the aedeagus base with two cranially curved lateroventral spines (Fig. 10J–K); the largest, of variable length, is on the anterior margin, and the thinnest is in the center (Fig. 10J); the anterior margin of the aedeagus base is semi-arched and has a row of small spines, variable in number. The aedeagus base has distally two small hooked spines directed toward each other (Fig. 10J–K). Velum hump-shaped with ventrodistal margin curved inwards; apex bifurcated, the largest portion scythe- shaped, bent sharply to the right; dorsally the shortest spine is directed to the apex of the inferior process (Fig. 10J–M).

FEMALE GENITALIA. Caudal margin of the seventh sternite concave (Fig. 8F). Gonoplac wider distally, about 4.5 times as long as wide, with thin, small scattered setae, mainly on the ventral margin. Gonoplac ensiform, slightly curved upwards up to the dorsal margin of the anal style, touching it behind (Fig. 8E). Lateral margins of the IX tergite distinctly incurved caudally, leaving in the middle a thin channel deeply excavated.

Distribution and habitat

Restricted to the semi-arid coastal habitats, on the peninsula of the extreme eastern end of Madeira Island. It was only known on the rocky table-like islet of the Ilhéu Chão (China 1938; Lindberg 1961). It is probably monophagous on the halophyte Suaeda vera. As in our case, Wollaston collected specimens of this species in May (11 May 1959) (Lindberg 1961).

Remarks

In this study, Cixius chaoensis is transferred to Tachycixius, due mainly by the presence of tubercles on the apical margin between veins; hindwings without the protrusion at the end of Cu2; two lateroventral spines on the left margin of the aedeagus basal-directed and the absence of a medial keel.

The aedeagus is like that represented by China, except for the ventral process of the apex which is more curved to the right, and the distal margin of the parameter which is more rounded. Most of the specimens examined do not show the three wing bands reported by China (1938).

China (1938) did not designate a holotype. However, he described both male and female and mentioned: “Habitat: Northern Dezerta, (Ilheo Chão); 6 ♂♂, 2 ♀♀ (WOLLASTON Coll.)”. The collection of Wollaston is in the Natural History Museum of London. The curator of Hemiptera of this museum, M.D. Webb, found the 8 specimens of the type series which consist of a male labelled “type” and 7 (5 males and 2 females) each labelled “ paratype ”. The specimen labelled “type” is designated here as lectotype. The specimen was studied by photo (NHMUK).