Micronecta major Chen, 1965

Tinerella, Paul P., 2013, <strong> Taxonomic revision and systematics of continental Australian pygmy water boatmen (Hemiptera: Heteroptera: Corixoidea: Micronectidae) </ strong>, Zootaxa 3623 (1), pp. 1-121 : 53-55

Micronecta major Chen, 1965

( Figs. 31–34 )

Micronecta major Chen, 1965: 160 .

Micronecta major: Wróblewski, 1972b: 524 . [list]

Micronecta major: Cassis and Gross, 1995: 68 . [catalog]

Micronecta major: Andersen and Weir, 2004: 248 , 335. [key; list]

Diagnosis: The largest Australasian micronectid, easily recognized by size, conically produced head, distinct hemelytral patterning ( Figs. 31a–b ), and distinct male genitalia ( Figs. 33a–g ). Females recognized on the combination of size, hemelytral patterning, prothoracic lobe ( Fig. 32a ), and metaxyphus ( Fig. 32b ). Possibly confused only with Micronecta robusta Hale based on size, however, readily distinguished by characters given in the key.

Size: ( Table 11). Brachypterous form: 4.0 ( Chen 1965). Macropterous form: 4.15–4.54. No brachypterous specimens examined during this research.

Derivation of specific epithet: From the Latin major , meaning larger, describing the large size of this species.

Notes on type material: Chen (1965) reported depositing the holotype, allotype, and two females in HNHM, and two female paratypes in SEMC. I was unable to obtain the holotype for examination. I was able to examine the two female paratypes from SEMC.

Description: Based on macropterous form. Measurements. Length: male 4.15–4.51; female 4.42–4.49; Width: male 1.97–2.1; female 2.04–2.09; Width of head: male 1.35–1.48; female 1.39–1.44; Synthlipsis: male 0.50–0.58; female 0.52–0.55; Width of eye: male 0.37–0.48; female 0.42–0.44; Width of pronotum: male 1.28–1.56; female 1.43–1.51; Length of pronotum: male 0.41–0.50; female 0.44–0.48.

Color: Ground color light brown ( Figs. 31a–b ). Head light brown, eyes reddish-black. Vertex, frons, and clypeus unicolorous, genae infuscated laterally. Labium brownish-black. Antennae pale brown. Pronotum dark brown, unicolorous with narrow, dark apical band. Scutellum dark brown, pruinose basally. Clavi each with basal broad, pale diagonal area well-developed, medial and apical portions same ground color as rest of hemelytra. Lateral portions with narrow, dark longitudinal line spanning length. Corium light brown, with two or three dark longitudinal lines prominent in medial portion. Prenodal embolar area long, infuscated in medial portion, postnodal embolar area developed, infuscated medially. Left membrane of both sexes hyaline. Venter of both sexes pale brown. Natatorial setae of metatarsus slightly darker brown.

Structural characteristics: Ratio of body length/width: males 2.15; females 2.16. Head width nearly equal to pronotal width, synthlipsis 1.2 times as wide as posterior width of eye. Ocular index: males and females 1.22. General facies of head (vertex, frons, and labium) proportionate. Third antennal segment densely pilose, long, parallel-sided, apex broadly rounded, segments one and two very short. Pronotum robust, convex, widest at middle with lateral margins weakly tapered and squared, about three times as wide as long (W/L: males 1.42/0.45; females 1.47/0.46). Prothoracic lobe short, relatively broad, with lower and posterior margins rounded ( Fig. 32a ). Hemelytral microsculpturing consisting of small, dense meshes distributed over entire surface. Short setae uniformly distributed over entire hemelytral surface. Metathoracic wings well-developed, reaching to apex of hemelytra. Lateral spines on abdominal segments IV–VIII: IV: one stout, short spine, two thin, long setae; V: two stout, short setae, one long, stout seta, one long, thin seta; VI: two stout, short setae, one long, thin seta; VII: two short, stout spines, one long, stout spine, one long, thin seta; VIII: eight stout, short spines, one long, thin seta. Metaxyphus of both sexes narrow, long and triangular, with apex broadly rounded ( Fig. 32b ).

Male foreleg ( Fig. 32c ): femur with two short, stout spines in basal third near ventral surface. Tibia with one short spine in apico-ventral portion and one short seta medio-apically. Pala with seven setae of varying lengths dorsally; eight setae in upper palar row and 16–18 setae in lower palar row, lower row setae more pronounced than those of dorsal row. Apex of pala with a shorter thickened seta. Palar claw ( Fig. 32d ) nearly crescent-shaped, apex rounded. Female foreleg with same general setal arrangement as male. Mesotarsal claws equaling nearly one-half the length of the mesotarsus.

Lateral lobes of abdominal tergum IV broad, asymmetric, and rounded apically. Right lobe longer, with 19 long setae, left lobe with 20 long evenly spaced, apically placed setae. Prestrigilar flap of tergal segment V as in Figure 32e . Strigil well-developed, very long and narrow, with few combs. Median lobe of sternite VII ( Fig. 32f ) narrowed basally, with numerous scattered setae, apex long, produced, rounded. Free lobe of tergite VIII ( Fig. 32g ) broad, triangular in outline, outer angle narrowly rounded and inner angle comparatively long. Setae of varying lengths placed over entire apical portion and numbering about 33. Pars stridens processus cleaner ridges of tergite VIII not examined. Male left paramere ( Figs. 33a–f ) long, narrow, and parallel-sided in lateral view, apex broadly produced, bluntly squared, apical scales present in inner portion before bluntly produced tip. Base broad, upper portion reaching nearly to middle of paramere shaft, lower portion of base short, nearly quadrate ( Figs. 33a–e ). Right paramere ( Figs. 33a–g ) very long, convexly curved, and nearly parallel-sided, tip slightly expanded and rounded ( Figs. 33e–f ). Base long, triangular, and widened, with lower portion rounded. Pars stridens processus consisting of about 35 plectral ribs spanning lower portion of paramere base ( Fig. 33g ). Aedeagus broad, as in Figures 33a–e .

Distribution and Habitat: ( Fig. 34 ). AUSTRALIA: New South Wales, Queensland. The species is newly recorded here for Queensland; the Brisbane records extending the species range from eastern New South Wales northward. A seemingly uncommon species as indicated by the few specimens examined during this research. Little habitat or ecological data are available, however, two male specimens examined in this research were collected from rivers, at the bank’s edge.

Discussion: This very large species is undoubtedly related to other taxa of the Micronecta annae species group. The general shape of the male left paramere ( Figs. 33a–f ) is similar in lateral aspect to that of M. robusta ( Figs. 37c–g ), however, in the dorsal aspect, the left paramere of M. major is well-produced and rounded apically. The abruptly expanded apex of the male right paramere of M. major differs from the pointed apex seen in the right paramere of M. robusta .

The general form of M. major is similar to that of other species of the M. annae species group, notably M. robusta , M. annae , and M. tasmanica . The large size of this species, unique male genitalia, and combination of female characters will serve to easily separate M. major from other species of the M. annae species group.

Specimens examined: AUSTRALIA: New South Wales: 16 km N Mudgee. 29-XI-1982. D. S. Horning, Jr. (2♂). [ ANIC] ; New South Wales: Hawkesbury-Nepean River System, Code N78. 14-I-1999. Edge. B. F. (3♂, 1♀). [ AMBS: AMSA] ; New South Wales: Hawkesbury-Nepean River System, Wallacia Bridge. 33 51 57S; 150 38 17E. 27-IX-1999. Edge. Ecology Lab. (1♂). [ AMSA] ; New South Wales: Hawkesbury-Nepean River System, Wallacia Bridge. 27-XI-1999. Edge. Ecology Lab. (1♂). [ AMSA] ; Queensland: Brisbane University , Queensland. 29-IX-1980. M. E. Pion & C. V. Reichart. (2♂). [ USNM] .

Figures

FIGURE 31. Micronecta major Chen. a. Male. b. Female. Scale bars = 0.5 mm.

FIGURE 32. Micronecta major Chen. a. Prothoracic lobe, female. b. Metaxyphus. c. Left male foreleg, posterior aspect. d. Left male pala (tarsus), anterior aspect, palar claw folded in. e. Prestrigilar flap of abdominal segment V. f. Sternal process of abdominal segment VII. g. Free lobe of abdominal tergum VIII. Scale bars = 0.1 mm.

FIGURE 33. Micronecta major Chen, male genitalia. a. Left paramere, lateral aspect, right paramere, dorsal aspect. b. Left paramere, dorso-lateral aspect, right paramere, lateral aspect. c. Left paramere, dorso-lateral aspect (cf base Fig. a,b,e), right paramere, lateral aspect. d. Left paramere, medio-ventral aspect, right paramere, dorso-lateral aspect. e. Left paramere, dorsofrontal aspect, right paramere, latero-frontal aspect. f. Left paramere, tip, right paramere, tip. g. Pars stridens processus, base of right paramere.

FIGURE 34. Distribution of Micronecta major Chen.

FIGURE 37. Micronecta robusta Hale. a. Metaxyphus. b. Sternal process of abdominal sternite VII. c. Free lobe of abdominal tergite VIII. d. Left paramere, lateral aspect. e. Left paramere, lateral aspect, right paramere, dorsal aspect. f. Left paramere, fronto-lateral aspect, right paramere, fronto-lateral aspect. g. Left paramere, medio-ventral aspect, right paramere, lateral aspect. h. Pars stridens processus, base of right paramere.