Sycanus aurantiacus

Ishikawa, Tadashi, Toriumi, Wataru, Susila, Wayan & Okajima, Shûji, 2007, Sycanus aurantiacus (Hemiptera: Heteroptera: Reduviidae), a new harpactorine species from Bali, Indonesia, with brief notes on its biology, Zootaxa 1615, pp. 21-27 : 22-26

Sycanus aurantiacus Ishikawa et Okajima, sp. nov.

(Figs. 1–17)

Description. Male (holotype). Body (Figs. 1, 2) mostly blackish. Antennal segment I with 2 orange annulations at basal fifth and apical third; basal annulation about twice as long as apical one. Rostral segments II and III yellowish brown (Fig. 2). Posterior pronotal lobe slightly paler than anterior. All femora with 2 incomplete orange annulations (Figs. 1, 2); all tibiae with narrow orange annulation subbasally. Veins on hemelytral corium (Fig. 1) pale yellow to yellowish brown; hemelytral membrane transparent, tinged with brown. Abdomen (Fig. 2) irregularly mottled with orange to brown markings, laterotergites III to VII orange medially. Short decumbent pubescence on thorax and abdomen often sprinkled with whitish wax.

Head ( Fig. 5 ) dorsally and laterally covered with erect setae intermixed with short, decumbent setae on entire surface, about 2.8 times as long as width across eyes, about 1.5 times as long as pronotum; anteoculus 0.8 times as long as postoculus, twice as long as length of eye in lateral view. Eyes about 0.7 times as wide as interocular space in dorsal view. Antennal segment I and basal half of segment II covered with erect and suberect setae; longest setae about 1.5 times as long as maximum width of segment I; apical half of segment II covered with short, suberect setae; segments III and IV sparsely covered with short, erect setae intermixed with short, decumbent setae; approximate proportion of segments I to IV 11: 5: 3: 10. Rostral segment I sparsely covered with erect setae; segments II and III almost bare; approximate proportion of segments I to III 7: 11: 2.

FIGURE 1–4. Sycanus aurantiacus sp. nov., 1–2, male (holotype), dorsal (1) and lateral (2) views; 3–4, female, dorsal (3) and lateral (4) views. Scale bars: 3.0 mm.

Pronotum ( Figs. 5, 6 ) 0.85 times as long as humeral width, each anterolateral angle with low, rounded tubercle; anterior lobe about 0.7 times as long as posterior lobe, deeply sulcate in posterior third along midline, covered with short, decumbent and long, erect setae anteriorly and laterally, and discally with some linear markings composed of short and decumbent, and long and erect setae; posterior lobe weakly tumid in middle near posterior margin ( Figs. 5, 6 ), covered with long, erect setae intermixed with short, decumbent setae; posterolateral and posterior margins straight. Scutellum covered with long, erect setae intermixed with short, decumbent setae, with scutellar spine posteriorly; scutellar spine ( Figs. 7, 8 ) erect and short, rounded at apex, not bifurcate apically, covered with long, erect setae. Thoracic pleura and sterna covered with long, erect setae intermixed with short, decumbent setae. Hemelytra exceeding apex of abdomen by about one-twentieth of length of former; coria covered with short, decumbent setae. Legs with long, erect setae of variable length; longest setae as long as maximum width of profemur; each femur more densely covered with short, erect setae ventrally than on its remaining surface.

Abdomen ( Fig. 9 ) nearly parallel-sided in dorsal view, about 2.2 times as long as width, covered with long, erect or suberect setae intermixed with short, decumbent setae. Laterotergites ( Fig. 9 ) weakly extended dorsad; laterotergite III weakly protuberant laterad at posterior corner; laterotergite IV slightly protuberant laterad at posterior corner, twice as long as minimum distance from most extended point of its lateral margin to spiracle IV; laterotergites V and VI each 2.5 times as long as minimum distance from most extended point of respective lateral margin to respective spiracle, with straight lateral margin.

Male paratypes. Pygophore ( Figs. 11, 12 ) dorsoapically with pair of foliaceous projections at base of posterior process; foliaceous projections rounded in posterior view, directed upwards; posterior process large, strongly projecting laterally near apex, rounded apically, weakly protuberant posteriorly at apex, posteriorly with longitudinal sulcus along meson in basal half. Paramere ( Fig. 13 ) widened in apical half, curved downwards, rounded at apex, covered with erect, short to long setae in apical half. Endosoma of phallus ( Fig. 14 ) armed with large sclerite dorsobasally, and with two pairs of spine-like sclerites and three pairs of small conical sclerites; dorsobasal large sclerite somewhat compressed laterally, upturned apically, nearly triangular in lateral view.

Female paratypes. Very similar to male (Figs. 3, 4). Head about 1.4 times as long as pronotum. Anterior pronotal lobe about 0.6 times as long as posterior lobe. Abdomen ( Fig. 10 ) weakly extended laterally in dorsal view, about 1.7 times as long as width; laterotergite IV 1.7 times as long as minimum distance from most extended point of its lateral margin to spiracle IV; laterotergites V and VI each 1.8 times as long as minimum distance from most extended point of respective lateral margin to respective spiracle, with slightly concave lateral margin. Valvifer I (Fig. 15) roundly projected at apex; valvula I (Fig. 15) rounded at outer-posterior angle and nearly angulated at inner-posterior angle, with straight posterior margin. Valvula II acutely extended at outer-posterior corner, rounded at inner-posterior corner, with outer-lateral margin gently concave. Styloides (Fig. 17) triangular, deeply incised in middle, sclerotized laterally, with a pair of elliptic sclerites at apex.

Intraspecific variation. Middle part of each tibia ranging from brownish orange to blackish. Apex of scutellar spine varying from just rounded to weakly tumid at lateral corners.

Measurements (mm; holotype, and paratypes in parentheses). Body length 17.5 (16.0–18.0 in males, n=8; 18.5–19.5 in females, n=8). Head length 4.7, width across eyes 1.7; length of anteoculus 1.7, of postoculus 2.1; antenna length 14.4, lengths of antennal segments I to IV 5.5, 2.4, 1.4, and 5.1; rostrum length 6.0, lengths of rostral segments I to III 2.1, 3.3, and 0.6. Length of pronotum 3.2, width across humeri 3.7; length of anterior pronotal lobe 1.3, of posterior pronotal lobe 1.9. Hemelytron length 11.5. Lengths of femur, tibia, and tarsus of proleg 5.9, 6.8, and 1.0; of mesoleg 5.3, 6.4, and 1.0; of metaleg 7.3, 9.0, and 1.1.

Type series. Holotype: ♂ (Figs. 1, 2, 5–9), “[ INDONESIA] Pancasari, Buleleng, Bali, 8 ° 15 ’ 12 ” S, 115 ° 0 9 ’ 0 9 ” E, 1280m, alt., 10.i.2007, W. Toriumi. ” Paratypes: Bali: same data as holotype, 6♂, 4Ψ (one shown in Figs. 3, 4; another in Fig. 10 ); same locality as holotype, 1♂ ( Figs. 11–14 ), 1Ψ, 9.viii.2006, T. Ishikawa, 1♂, 3Ψ (one shown in Figs. 15–17), 17.i.2007, W. Toriumi.

Distribution. Bali, Indonesia.

Etymology. From the Latin, aurantiacus , referring to the yellow to yellowish brown veins of the hemelytral coria; an adjective.

Remarks. This new species is separable from the other members of Sycanus by the following combination of character states: body mostly blackish; antennal segment I with two orange annulations; posterior pronotal lobe weakly tumid in middle near posterior margin; scutellar spine erect and short, rounded at apex; each femur with two incomplete orange annulations; hemelytral corium blackish with veins yellow to yellowish brown; and laterotergites of abdomen weakly extended dorsad.

Biology. As far as is known, this new species has been collected from crop fields in highland (more than 1,000 m altitude) of Bali. It was found on leaves of cultivated cabbages and walls of greenhouses under plentiful sunshine. One adult was also obtained from a cluster of dead leaves of a banana tree in the crop field.

In the cabbage field, certain individuals of this reduviid were observed to feed on larvae of moths, including such destructive insect pests of Brassicaceae crops as Crocidolomia pavonana (Fabricius, 1794) (Crambidae) and Plutella xylostella (Linnaeus, 1758) (Yponomeutidae) . This suggests that the new species is a natural enemy, and could be a biological control agent against these insect pests. Moreover, early instars of the assassin bug preyed upon flies and eggs of spiders, indicating a wide range of food preferences. It is expected that mass-rearing could easily be conducted for this reduviid. (See also Ambrose 1999.)

Figures

FIGURE 5 – 10. Sycanus aurantiacus sp. nov. (setae omitted), 5, head and prothorax, lateral view; 6, pronotum, posterior view; 7 – 8, scutellar spine, lateral (7) and posterior (8) views; 9 – 10, abdomen (genitalia omitted), male (9) and female (10), lateral view. Scale bars: 1.0 mm. Abbreviations: lt 3, laterotergite III; lt 4, laterotergite IV; lt 5, laterotergite V; lt 6, laterotergite VI.

FIGURE 11 – 14. Sycanus aurantiacus sp. nov. (setae omitted), 11 – 12, pygophore, lateral (11) and posterior (12) views; 13, left paramere, lateral view; 14, phallus (endosoma retracted), lateral view; 15, right valvifer I and valvula I, ventral view; 16, right valvula II, ventral view; 17, styloides, ventral view. Scale bars: 0.5 mm. Abbreviations: cs, conical sclerite; dls, dorsobasal large sclerite; es, elliptic sclerite; fp, foliaceous projection; pp, posterior process; ss, spine-like sclerite; vf 1, valvifer I; vv 1; valvula I.