Ptilomerella, Zettel, 2009

Zettel, H., 2009, Three new genera of Ptilomerinae (Hemiptera: Heteroptera: Gerridae) from Southeast Asia, Zootaxa 2046 (1), pp. 26-42 : 31-32

Ptilomerella gen. n. ( Figs. 8 –24)

Type species. Ptilomerella akekawati sp. n. (by present designation)

Diagnosis. Small Ptilomerinae of predominately yellowish brown colour ( Figs. 8, 9 ) (greenish if alive); meso- and metacetabula and lateral portions of tergites 2–5 with very dense, silvery, strongly shiny hair layer which completely covers integument. Antennomere 4 without sulcus. Protarsus short (Fig. 13). Metafemur slightly longer than mesofemur, both with pale distal portions. Metatarsomeres fused. Male with foreleg hardly incrassate (Fig. 13), mesofemur with or without long pilosity (dimorphic), and small genitalia; pygophore (Fig. 14) distally with short, stout setae; proctiger (Fig. 15) small, on each side with an acute and a blunt angular projection; paramere (Figs. 16, 17) strongly sclerotized, with lateral hook-shaped process, and lateral sclerites in vesica (Figs. 18, 19) of slender triangular shape. Female with moderately shortened abdomen ( Fig. 9 ) and a deep transverse fold on sternite 7 separating short mediodistal portion with narrow, folded medial lobe (Figs. 23, 24).

Description. Only apterous morph and one dealate male known. Body length 6.3–7.6 mm, female on average larger than male. Yellowish brown; head with narrow, V- or M-shaped, black (or brown) mark; pronotum with black lateral stripes; meso- and metanotum surrounded by narrow black lines, mesonotum in addition with narrow infuscated midline (only in apterous specimens visible). Acetabula distally with black marks. Meso- and metacetabula and lateral portions of tergites 2–5 with very dense, silvery, strongly shiny hair layer which completely covers integument. Legs mainly yellowish brown to orange, profemur with two distinct stripes, protibia and protarsus blackish or partly reddish brown, meso- and metafemora each with one thin black stripe at base and distal part pale; tibiae and tarsi of middle and hind legs orange to pale. Head ( Fig. 8 ) with larges eyes, minimum distance of eyes 0.3 times head width, and moderately pronounced antenniferous tubercles. Antenna blackish, slender and very long, antennomere 1 subequal in length with antennomeres 2–4, antennomere 4 without sulcus. Flexor side of profemur with numerous stout setae at base and one minute tooth subapically (Fig. 13); protarsus short. Metafemur slightly longer than mesofemur. Metacoxa without spine. Hind leg with two small but distinct claws. In dealate specimen wings broken off at base.

Male. Profemur hardly enlarged (Fig. 13). Mesofemur polymorphic, with or without long pilosity. Genitalia small. Pygophore (Fig. 14) short, distally with some short, stout setae. Proctiger (Fig. 15) small, on each side with acute and blunt angular projection. Paramere (Figs. 16, 17) strongly sclerotized except transparent apex, without recognizable pilosity, with hook-shaped process at lateral face at about midlength. Vesica sclerites (Figs. 18, 19) slightly asymmetrical: Dorsal sclerite and ventral sclerites completely fused. Dorsal sclerite distally recurved and strongly enlarged, on right side with distinct subapical protuberance. Ventral sclerite with very short distal arm on right side and long, slender distal arm on left side supporting long ductus seminalis. Lateral sclerites subsymmetrical, elongate triangular, distinctly broadened at middle or at distal fourth. Second lateral sclerites on vesica's lateral lobes present, variable in size.

Female. Metanotum, abdominal segments 1–6, and venter of thorax and abdomen without modifications. Abdomen moderately shortened ( Figs. 9 , 11 ). Connexiva hardly flapped mediodorsad over posterior tergites ( Figs. 9 , 11 , 22). Tergites 7 and 8, and proctiger simple, directed posteriad or posteroventrad, respectively (Figs. 20, 21). Distal portion of sternite 7 separated by deep, transverse fold, distal section forming a narrow, folded medial lobe (Figs. 23, 24). Gonocoxae 1 (Figs. 20, 21, 23, 24) large, plate-like, more or less exposed.

Comparative notes and discussion. Ptilomerella gen. n. belongs clearly to the Ptilomera genus group, that contains Ptilomera , Archaeoptilomera gen. n., and—distantly— Potamometra . Characteristics of this group are, e.g., the absence of a sulcus on antennomere 4, the whitish apical part of meso- and metafemora, the shiny areas of the dorsum, and the comparatively long metafemur. Ptilomerella akekawati sp. n. is much smaller than these genera, and differs by the more spindle-shaped body. The bright silvery patches of pilosity on acetabula and tergites, the paramere process of the male, and the female's sharply delimited distal section of sternite 7 are unique within Ptilomerinae . In the field, Ptilomerella akekawati sp. n. appears similar to nymphs of syntopic Ptilomera species , but it can be recognized by the more conspicuous silvery patches. A polymorphism in the pilosity of the mesofemur of the male is unique in Ptilomerinae . Hitherto such pilosity was known as an important autapomorphy of Ptilomera s.l. Its phylogenetic origin and significance within the genus group remains uncertain as long as the male of Archaeoptilomera gen. n. is unknown.

Distribution. Southern Thailand (Surat Thani, Phang-Nga, Phuket) and southern Myanmar (Kayin State).

Etymology. The generic epithet refers to the close relationship with Ptilomera and to the small body size. Gender: feminine.

Included species. Ptilomerella akekawati sp. n., Ptilomerella anderseni sp. n.

Figures

FIGURES 8–9. Ptilomerella gen. n. (8, 9) P. akekawati sp. n. (8) Habitus of apterous male (paratype; body length 6.3 mm), dorsal aspect. (9) Habitus of apterous female (paratype; body length 7.2 mm), dorsal aspect. © NHMW Hemiptera Image Collection, published with permission.

FIGURES 10–11. Ptilomerella gen. n. (10, 11) P. anderseni sp. n. (10) Habitus of macropterous male (holotype; body length 6.4 mm), dorsal aspect, appendages omitted. (11) Habitus of apterous female (paratype; body length 7.4 mm), dorsal aspect, appendages omitted. © NHMW Hemiptera Image Collection, published with permission.