Ochterus stysi, Polhemus & Polhemus, 2008

Polhemus, Dan A. & Polhemus, John T., 2008, A new Indian Ocean species of Ochterus from the island of Mauritius (Hemiptera: Heteroptera: Ochteridae), Acta Entomologica Musei Nationalis Pragae 48 (2), pp. 281-288 : 282-286

Ochterus stysi sp. nov.

(Figs. 1-5) Type material. HOLOTYPE: J (macropterous), MAURITIUS: BLACK RIVER DIST.: stream 1.2 km. S. of Chamarel, 200 m. [650 ft.], water temp. 22.5° C., 22 October 1986, CL 2232, D. A. Polhemus and J. T. Polhemus (BPBM). PARATYPES: MAURITIUS: BLACK RIVER DIST.: 2 JJ 9 ♀♀, same data as holotype (BPBM, JTPC).

Description. Male. General form broadly ovate, body length 4.90, maximum width (across hemelytra) 2.60 (Fig. 1). Coloration dark reddish brown, with scattered pruinose lavender mar-

kings as follows: small, transverse patches along posterolateral sections of pronotum immediately behind eyes; four small irregular patches arranged transversely between anterior and posterior lobes of pronotum; small, longitudinally elongate, semi-triangular patch medially at anterior margin of scutellum; 7-8 small, irregular patches arranged symmetrically on basal halves of clavus and corium; two larger, roughly circular patches laterally on posterior half of embolium; single large, roughly circular patch at posterolateral angle of corium adjoining base of wing membrane; 7 small, irregular patches of varying size scattered on wing membrane. Head shining black; eyes very dark red; anterior margin of clypeus, labrum, and rostrum chestnut brown; anterolateral flanges of pronotum, small transverse patch posteromedially on pronotum, and narrow margin along lateral edge of embolium dark yellow; antennae with segments I and II dull brownish yellow, segments III and IV dark brown; thoracic venter dull pruinose black; legs and abdominal venter yellowish brown; hind tibiae bearing very small dark brown spots at bases of spines.

Fig.1. Ochterus stysi sp. nov., male, dorsal habi- Head glabrous, length (along midline as mea- tus, with stippling indicating distribution of pale sure from directly above) / width (across eyes) = markings on dorsum. Appendages omitted. 0.50/1.70, angled downward at 45° when viewed laterally; vertex with numerous striae; eyes large, protruding, projecting posterolaterally beyond vertex; antennae with segments I and II short, globose, segments III and IV slender, filiform, lengths of segments I-IV = 0.10, 0.20, 0.40, 0.30; rostrum long, length = 2.90, exceeding hind coxae and extending onto base of abdominal venter. Pronotum length (midline) / width = 1.10/2.50, bearing numerous small pruinose punctations, every punctation bearing a very short pale seta; anterior collar prominent, flat; anterolateral margins explanate, well demarcated from disk; calli barely tumescent; posterior margin multisinuate, posteriorly concave centrally above base of scutellum. Scutellum triangular, length / width = 0.90/1.30, weakly tumescent, bearing numerous small pruinose punctations centrally plus a double row of slightly larger, more closely spaced punctations along lateral margins, each punctation bearing a tiny, pale seta. Hemelytra long, attaining tip of abdomen, with corium, clavus and embolium well defined, surfaces set with scattered pruinose punctations, each punctation bearing a tiny, pale seta; anterolateral embolar margin narrowly explanate; length of clavus along outside margin 1.80; membrane venation evident, defining 6 closed cells.

Ventral surface of thorax smooth and pruinose, bearing patches of long, upright, gold setae along the inner margins of the meso- and metepisterna; scattered tiny, dark punctations present on pro-, meso-, and metaepisterna; abdominal venter covered with very short, fine, appressed gold setae, this setal covering interrupted by ovate glabrous patches surrounding spiracles laterally on paratergites. Legs with all segments covered by short, fine, recumbent gold setae; all coxae bearing long, gold setae ventrally; fore and middle femora each with a very long, erect gold setae ventrobasally, remainder of ventral margins bearing moderate length, upright, gold setae; hind femur broadly and gently bowed downward when viewed laterally; anterior and middle tibiae bearing numerous short, bristly gold setae, these setae becoming more numerous distally; fore and middle tibiae with a few longer semi-erect spinelike setae on posterior margins; hind tibia with double longitudinal row of scattered large, erect, gold spines; all tibiae with transverse rows of spines at distal ends; claws gold, gently curving, arolia long, exceeding length of claws when viewed laterally. Lengths of leg segments as follows: fore femur / tibia / tarsal 1 / tarsal 2 = 1.20/1.20/0.10/0.10; middle femur / tibia / tarsal 1 / tarsal 2 = 1.50/1.20/0.20/0.10; hind femur / tibia / tarsal 1 / tarsal 2 / tarsal 3 = 1.60/2.10/0.05/0.30/ 0.20.

Genital segment well retracted into abdomen; subgenital plate with V-shaped indentation medially on posterior margin. Pygophore with caudal tip quadrate, apex transverse, lateral lobes well removed from apex ( Fig. 5 ). Right paramere with head of moderate height, evenly domed and convex; appendices moderately long, apices indented to form two short apical processes, one of these processes large, with tip rounded, the other smaller, with the tip serrate ( Fig. 3 ); paramere shaft stout, broadened distally ( Fig. 2 ).

Female. Similar to male in general structure and coloration, body length 5.40, width 2.80. Head length (along midline as measure from directly above) / width (across eyes) = 0.50/1.55; lengths of antennal segments I-IV = 0.10, 0.20, 0.40, 0.40; rostrum length = 2.80, exceeding hind coxae and extending onto base of abdominal venter. Pronotum length (midline) / width = 1.25/2.60. Scutellum length / width = 0.90/1.40. Hemelytra with length of clavus along outside margin 2.00. Lengths of leg segments as follows: fore femur / tibia / tarsal 1 / tarsal 2 = 1.50/1.20/0.10/0.10; middle femur / tibia / tarsal 1 / tarsal 2 = 1.30/1.50/0.20/0.10; hind femur / tibia / tarsal 1 / tarsal 2 / tarsal 3 = 1.80/2.40/0.05/0.30/0.20.

Differential diagnosis. Ochterus stysi sp. nov. may be separated from any other Ochterus Latreille, 1802 species presently described from India, Ceylon, Africa or Madagascar by the absence of three irregular or semicircular yellowish spots along the lateral margin of the hemelytron. These spots are present in both O. marginatus Latreille, 1804 and O. caffer Stål, 1855 , but absent in all species so far known from the Mascarene and Seychelles archipelagoes (see key below).

Within the insular Indian Ocean region east of Madagascar, O. stysi sp. nov. is the only member of the family Ochteridae currently known from the Mascarene Islands. It may be separated from its most geographically proximal congenor, O. seychellensis D. Polhemus, 1992 from the island of Mahe in the granitic Seychelles, by the smaller and less prominent pruinose patches on the hemelytra, particularly on the central corium bordering the clavus; by the dorsal surfaces of the hemelytra which bear scattered pruniose punctations on the clavus, corium and embolium, rather than having only a few very tiny punctations on the embolium as in O. seychellensis ; and by its larger in overall size (females over 5.0 mm and males over 4.5 mm, versus 4.0 mm and 4.3 mm respectively in O. seychellensis ).

The male genitalic structures of these two species are also diagnostic. Both share a well developed medial lobe on the pygophore with a broadly truncate apex (compare Fig. 5 with Fig. 2 in POLHEMUS (1992)), and an apically serrate subapical process on the male right paramere (compare Figs. 3-4 ). In O. stysi sp. nov., however, the apical portion of the right paramere is much larger and more elongate, and has a more broadly rounded apex (compare Figs. 3-4 ). Etymology. The name ‘stysi’ is a patronym honoring our entomological colleague Pavel Štys, who has produced many brilliant insights into the systematics and taxonomy of Heteroptera during his distinguished career.

Ecological notes. The type locality was a rocky upland stream partially shaded by disturbed montane forest. The stream had a moderate gradient, with the bed profile consisting of slow pools linked by shallow runs and boulder-strewn rapids. The banks consisted of mud and sand, being relatively steep and undercut in some places, but gently sloping in others. It was on exposures of open substrate along these banks that the type series of O. stysi sp. nov. was taken.

Other aquatic Heteroptera taken at the type locality included Mascarenisalda mametiana (Drake, 1953) (Saldidae) , Mesovelia vittigera Horváth, 1895 (Mesoveliidae) , Hydrometra mameti Poisson, 1951 (Hydrometridae) , Limnogonus cereiventris Signoret, 1862 (Gerridae) , Laccotrephes annulipes (La Porte), 1833 , Ranatra grandocula Bergroth, 1893 (Nepidae) , and undescribed species of both Rhagovelia Mayr, 1865 , and Microvelia Westwood, 1834 (Veliidae) .

Biogeographic notes. The endemic Ochteridae of the Mascarene and Seychelles archipelagoes represent an interesting biogeographical anomaly. In particular, they show little structural resemblance to any species occurring in geographically proximal continental regions such as Africa or India that might be considered logical source areas for overwater colonization. Extensive aquatic surveys by the authors across the length and breadth of Madagascar in 1985 similarly failed to reveal any Ochterus species that might represent close relatives to O. stysi or O. seychellensis . The only other centers of significant diversification for this family lie in New Guinea, Australia, and South America, which are far removed from the Indian Ocean islands.

Although their origins are obscure, we consider it likely that further species of endemic Ochteridae will be discovered in the Mascarenes, particularly on the high, rugged island of Reunion which lies approximately 200 km to the southwest of Mauritius. They should be searched for on open sand bars, moist earthen banks, or damp bedrock faces adjacent to streams at elevations between sea level and 1000 meters.

Figures

Figs.2-5. Indian Ocean Ochterus Latreille, 1802 species, male genitalia, structural details.2-3, 5 – Ochterus stysi sp. nov. 2 – male genitalia; 3 – appendix of male right paramere; 5 –pygophore, caudal tip. 4 – Ochterus seychellensis D. Polhemus, 1992, appendix of right male paramere.