Taxonomy of Micronectidae (Heteroptera: Nepomorpha) from Vietnam, with descriptions of 11 new species

The taxonomy of Micronectidae in Vietnam is reviewed. Based on our cumulative collections during 2001–2020, 11 new species of Micronecta Kirkaldy, 1897 are documented and described in this study: M. acuminata sp. nov., M. arcuata sp. nov., M. caperata sp. nov., M. clavata sp. nov., M. cultellata sp. nov., M. fulvopicta sp. nov., M. nieseri sp. nov., M. pingae sp. nov., M. sinuata sp. nov., M. undulata sp. nov., and M. vietnamica sp. nov. Nine species are recorded from Vietnam for the first time: M. decorata Lundblad, 1933, M. drepani Nieser, 2000, M. erythra Nieser, Chen & Yang, 2005, M. fugitans Breddin, 1905, M. johorensis Fernando, 1964, M. melanochroa Nieser, Chen & Yang, 2005, M. ornitheia Nieser, Chen & Yang, 2005, M. sahlbergi (Jakovlev, 1881), and M. tuwanoni Nieser, Chen, Leksawasdi, Thanyakam & Duangsupa, 2004. Thus, in this study, two genera and 37 species of Micronectidae are now reported from Vietnam: Synaptonecta Lundblad, 1933 with only one species, S. issa (Distant, 1910), and Micronecta with 36 species. A key to all species occurring in Vietnam, subgeneric diagnoses, and a key to all current subgenera of Micronecta are provided.


Comparative notes
In Southeast Asia, only two genera of Micronectidae occur: Micronecta Kirkaldy, 1897 andSynaptonecta Lundblad, 1933. They are closely related, but there are signifi cant structural differences between the two genera, as summarised by , , and Chen et al. (2005).
The genus Micronecta can be recgonised by the following characterstics: the vertex is usually convex and rarely fl attened; the pronotum is usually well-developed and convex; fore tibia and pala of the male are separated; the strigil on abdominal tergite VI is usually present; the apex of the membrane in the brachypterous morph is truncate or broadly rounded. The body of species of Micronecta is ovate or subparallel sided, with length between 1.0 and 4.4 mm.
In contrast, Synaptonecta can easily be separated from the abundant Micronecta by the fusion of the fore tibia and pala in both sexes, the concave vertex, and the pointed apex of the membrane in the brachypterous morph (also see Wróblewski 1972a;Chen et al. 2005). The body of species of Synaptonecta is ovate, with length between 1.8 and 2.6 mm.

Remarks on the current subgeneric classifi cation of Micronecta Kirkaldy, 1897
Several subgenera of Micronecta were established by  and .  also introduced several species groups of Micronecta, recognised below the subgeneric rank, but this species group classifi cation was hardly used by subsequent entomologists. However, many species were not formally assigned to any subgenera because they did not fi t the defi nition of any subgenus (Štys & Jansson 1988;Tinerella 2008Tinerella , 2013. In many cases, those species which do not fi t any subgenus were just placed, although tentatively, into the nominate subgenus Micronecta (see Jansson 1995). This classifi cation scheme was questioned by Tinerella (2008Tinerella ( , 2013, but no resolution was made. Tinerella (2008Tinerella ( , 2013 only attempted to reconstruct phylogenetic relationships between micronectid genera occurring in New Guinea and Oceania. , and Nieser & Chen (1999) refrained from using a subgeneric classifi cation for the same reason, but subsquently Nieser et al. (2005) and Chen et al. (2015) used a subgeneric classifi cation again, without clear explanation about the switch in their opinions. Nieser et al. (2005) even described a new subgenus, Unguinecta , to include several species.
It is notable that several subgenera, e.g., Ctenonecta , Indonectella Hutchison, 1940, Lundbladella Wróblewski, 1967, and Pardanecta Wróblewski, 1962, were defi ned just based on only a few aberrant morphological features, which are potentially homoplasious (e.g., the shape of the palar claw of the male, the absence of a strigil in some subgenera, the shape of the free lobe of tergite VIII, or even the general morphology of the left paramere). On the other hand, the diversity of Micronecta is still poorly known; thus, the current taxonomy of Micronecta does not yet satisfactorily refl ect natural relationships among subgeneric taxa. Our present paper illustrates this situation, with a high number of previously unknown species showing an aberrant morphology. A comprehensive phylogenetic analysis is certainly needed for resolving the systematics of the genus Micronecta. However, this type of work requires extensive taxon sampling across the very large distribution range of Micronecta as a whole, together with sampling of relevant DNA sequence data. This is beyond the scope of our present study, but we hope it can be achieved in the future.
While pending such comprehensive phylogenetic analyses, we perceive that the current subgeneric classifi cation is still useful for the identifi cation and comparative morphology of species of Micronecta, and to some extent it refl ects the great diversifi cation of the genus. Therefore, we indicate the subgeneric position of all species treated in the present paper, largely according to defi nitions of subgenera by  and Nieser et al. (2005). Among the 11 recognised subgenera, Mesonecta Poisson, 1938 and Micronectella Lundblad, 1933 do not occur in Vietnam. We note that some species in this paper do  Breddin, 1905 10. Palar claw narrow and nearly straight ( Fig. 2A) Nieser, Chen & Yang, 2005 -Markings  30. Shaft of left paramere with notch on lateral margin, set basally to triangular projection (Fig. 14D); right paramere strongly bent before club-shaped apex, forming angle of nearly 90° on lateral margin (Fig. 14C) 16D); shaft of left paramere tapering towards slightly swollen apex, sub-apically with small process (Fig. 16F); shaft of right paramere widened at distal part and folded into gutter-like structure, with lobe on mesial side (Fig. 16E) (Figs 17D,18D,19D); shaft of left paramere with one or two triangular projections on lateral margin (Figs 17F,18F,19F); shaft of right paramere modifi ed differently (Figs 17E,18E,19E (For extensive synonymy list, see Jansson 1995.)

Diagnosis
Body length 3.6-4.4; only macropterous form known. Pronotum distinctly longer than median head length. Hemelytron (Fig. 1A): corium with three longitudinal brown stripes, sometimes in broken pattern or indistinct; embolium with a set of four short brown stripes, sometimes confl uent into a long unbroken stripe.

Distribution
Vietnam: Hanoi and Ha Tinh ; Phu Tho, Dong Nai (fi rst records). Other countries: from Africa through Arabia, Palestine, southern Asia to Southeast Asia and southern China (Wróblewski 1968;Zettel et al. 2017).

Remarks
This is the largest species of Micronecta occurring in Vietnam. It has some similarities with M. sedula Horváth, 1905 andM. siva (Kirkaldy, 1897) in the structures of the male genitalia, but can easily be recognised by its larger body (also see Remarks under M. siva).
Males: fore femur with four spines in proximal third ventrally, four spines on middle third and a pair of spines on distal third dorsally; fore tibia with a pair of spines on distal third; palar claw slender, straight. Median lobe of sternite VII with two long setae. Free lobe sub-rectangular, posterior margin concave, lateral angle produced, with about 10 long setae (Fig. 2E). Left paramere: shaft stout, apical part slightly swollen, apex obtuse, mesial side with minute spine-like scales; basal lobe tongue-shaped (Fig. 2G). Right paramere: shaft slender slightly curved pre-apically, apex narrowly rounded (Fig. 2F).

Distribution
Vietnam: Nghe An and Ha Tinh ; Dong Nai (fi rst record). Other countries: widespread from India and Sri Lanka to China and Southeast Asia (Myanmar, Thailand, Indonesia) (Lunblad 1933b;Nieser & Chen 1999;.

Remarks
Among species of the subgenus Basileonecta, M. siva is unique in having distinct transverse stripes on the pronotum and dark longitudinal stripes on the hemelytra. The left and right parameres of M. siva look like those of M. sedula, but their detailed structures are clearly different. In M. sedula, the apex of the left paramere is swollen, and the shaft of the right paramere is curved at around on the distal fourth.
In M. siva, the apex of the left paramere is not swollen, and the shaft of the right paramere is curved at the distal third.
Among the three Asian species of the subgenus Basileonecta, M. sedula has similar marking patterns on the hemelytra to those of M. scutellaris, but it is a distinctly smaller species (body length not more than 3.4 mm), its left paramere is not twisted pre-apically, and its right paramere is not expanded pre-apically. Figs 1D, 2H-K Micronecta jaczewskii Wróblewski, 1962, fi gs 1-8 (type locality: Hanoi, Vietnam).
Males: fore femur with row of seven spines on proximal third ventrally; fore tibia without spine (Fig. 2H); palar claw, median lobe of sternite VII and free lobe ( Fig. 2I) as in diagnosis of Ctenonecta. Left paramere: shaft stout, apex blunt ( Fig. 2K). Right paramere: shaft broad at base, constricted at distal half, then expanded and constricted again before narrowly rounded apex; basal lobe with a distinct hump on mesial side, near base of shaft (Fig. 2J).

Remarks
The male of this species can easily be separated from other species of Micronecta by its distinct shape of the right paramere ( Fig. 2J), together with its unique palar claw (Fig. 2H) and the presence of combs of setae on the middle tibia.  24, 30-31, 43, 51, 58, 66, 74-75, 90 (redescription).
Males: fore femur with a pair of spines in proximal third, one spine on distal third dorsally; fore tibia with a pair of spines on distal margin; palar claw knife-shaped. Median lobe of sternite VII with a pointed apex and one long seta (see Chen et al. 2015: fi g. 58). Free lobe large, apically broadened, posterior margin produced into an obtuse angle, lateral angle with 10-15 long setae (Fig. 3A). Left paramere: shaft slender, constricted pre-apically, apex slightly twisted (Fig. 3C). Right paramere: shaft evenly curved, from distal fourth tapering towards narrowly rounded apex (Fig. 3B).

Distribution
First records for Vietnam. Other countries: mainly in Southeast Asia, from Thailand and Peninsular Malaysia to Indonesia (Sumatra, Java) and Borneo (Sabah) Chen et al. 2015).

Diagnosis
Body length 1.2-2.4. Pronotum about as long as median head length, slightly narrower than head width. Hemelytron (Fig. 1F) generally pale, with four indistinct, broken longitudinal brownish stripes.

Diagnosis
Body small, ovate, length 1.5-1.8 (brachypterous). Pronotum shorter than median head length. Dorsum colour pale yellowish. Pronotum with a pair of transverse brown marks. Dark patterns on hemelytra reticulate; embolium with fi ve dark patches; membrane reduced.
Males: fore femur with a pair of spines in proximal third ventrally, a large and two small spines in distal third, and a pair of spines distally; fore tibia with one spine on middle third, and a pair of spines on distal margin; palar claw narrow, parallel sided, apically bent ( Fig. 3G). Median lobe of sternite VII with two long setae and a serrated triangular apex. Free lobe: mesial angle broadly rounded, lateral angle produced, posterior margin straight, two long setae restricted to lateral angle. Left paramere: shaft relatively short and fl attened, on mesial side near the middle with a large triangular tooth, apex of shaft narrowly rounded; basal part with a prominent projection on opposite side of large subovate basal lobe (Fig. 3I). Right paramere: shaft stout, longitudinally striated, apex rounded (Fig. 3H).

Remarks
Nieser (2002a) already noted the similarities and differences between three closely related species M. johorensis, M. dentifera Nieser, 2002, andM. eucosmeta Hutchinson, 1940. These three species can be placed in the subgenus Dichaetonecta as they possess a rather narrow palar claw, and the median lobe of sternite VII bears two long setae. The longitudinally striated shaft of the right paramere is a unique diagnostic characteristic for M. johorensis. Also see Remarks under M. sahlbergi. Breddin, 1905Figs 1G, 4A-C Micronecta ludibunda Breddin, 1905a: 57 (type locality: Bogor, Indonesia).

Diagnosis
Body length 1.9-2.4. Pronotum slightly longer than median head length. Pronotum: with a pair of dark oval rings, somtimes fragmented, reduced to streaks and spots, or absent. Hemelytron (Fig. 1G): corium with four longitudinal brown stripes; embolium with three brown marks.

Remarks
Besides structural characteristics, M. ludibunda can usually be recognised by a pair of dark oval marks on the pronotum. This characteristic, however, is variable. In some specimens of M. ludibunda, the dark oval marks on the pronotum are fragmented, less distinct, or even absent. Micronecta ludibunda is also considered related to M. malayana Leong, 1966, from Peninsular Malaysia, in both the colour pattern of the pronotum and the general form of the left paramere
Males: fore femur with a set of four spines on proximal third ventrally; fore tibia without spine; palar claw narrow. Median lobe of sternite VII with one long seta and a long and narrowly rounded apex. Free lobe posteriorly strongly broadened, posterior margin nearly straight, lateral angle produced (Fig. 4D). Left paramere: shaft slender, mesial side with barbs, apical part sinuate, covered with small scales, apex narrowly rounded; basal lobe tongue-shaped (

Remarks
The fi ve species of Dichaetonecta occurring in Vietnam can easily be separated from each other by the structures of the left paramere. The left paramere of M. decorata is apically constricted and twisted. That of M. ludibunda is constricted before widening to a broad, fl at, and suboval apex. The left paramere of M. sahlbergi is uniquely sinuate at the apical part, which is covered with small scales. In M. desertana, the apical part of left paramere is rather simple, only slightly constricted, but neither twisted nor sinuate. The left paramere of M. johorensis has a large triangular tooth near the middle section of the shaft. The right paramere of M. johorensis is unique in having longitudinal striations on the stout shaft. In addition, the shape of the free lobe of M. decorata is clearly distinct from that of the other three species besides M. johorensis, with the posterior margin produced into an obtuse angle, while in the other three species the posterior margin of the free lobe is straight or slightly concave. The free lobe of M. ludibunda is more like that of M. sahlbergi, with both having a more strongly widened distal part. The free lobe of M. desertana is only slightly widened at the distal part. (Fieber,

Diagnosis
Body length 3.0-3.1. Pronotum slightly longer than median head length; clearly narrower than head width. Hemelytron ( Fig. 5A) translucent or greyish brown, usually with two broken longitudinal dark stripes; embolium with a large spot in the middle and two smaller spots on two sides.
Males: fore femur with a pair of spines on proximal third; fore tibia with a spine on middle third (

Remarks
This species can easily be recognised by the relatively large body (length ca 3.0 mm), the absence of a strigil, the shape of the the free lobe, and the shape of the apical part of the left paramere ( Fig. 6B, D).  Nieser et al. 2005;Polhemus 2017).

Remarks
In Vietnam, M. guttatostriata is one of two species without a strigil; the other one is M. grisea. Micronecta guttatostriata can be separated from the latter by its distinctly smaller size, with body length of around 2.0-2.4 mm, and the unique colour pattern of the pronotum. In addition, the shape of the free lobe and the parameres are reliable characteristics for identifying this species.   Figs 5C, 7A-C Micronecta drepani Nieser, 2000, fi gs 1-10 (type locality: northern Thailand). Micronecta drepani -Nieser et al. 2005: 190, 191 (notes, checklist). -Zettel et al. 2017: 40 (record Cambodia).
Males: fore femur with a pair of spines on proximal third, two spines distally; fore tibia with three spines on distal third ventrally; palar claw large, sub-triangular with straight apical margin. Median lobe of sternite VII short and broad with four long setae and an angular apex. Free lobe slightly expanded posteriorly, mesial angle rounded, lateral angle produced with ca 20 long setae (   & Yang, 2005: 191-192, 194, fi gs 1-11 (type locality: Yunnan, China).

Diagnosis
Body length 1.5-1.6 (brachypterous). Pronotum slightly shorter than median head length, lateral margins of pronotum short. Hemelytron light brown with scattered small red dots and distally with a transverse irregularly-shaped dark mark (Fig. 5D).
Males: fore femur with a pair of spines on distal third, one spine on dorsal margin of distal third and two spines dorsodistally; fore tibia with one spine on distal third; palar claw broadened distally, apex rounded. Median lobe of sternite VII short and broad, with four long setae and an angular apex. Free lobe slightly expanded at middle part, then tapering posteriorly, mesial angle rounded, lateral angle square, with ca 17 long setae (Fig. 7D). Left paramere: shaft broad, fl attened, lateral side with a distinct triangular projection, apex rounded; basal lobe length greater than its width, sub-trapezoid (Fig. 7F). Right paramere: shaft evenly curved, distal half parallel sided, apex rounded (Fig. 7E).

Distribution
Previously only known from China (Yunnan). First records for Vietnam (Phu Tho).

Remarks
According to the description by Nieser et al. (2005), the hemelytron of this species is marked with small red dots, but our specimens do not exhibit this characteristic. However, our sample is too small to determine whether intra-populational variations in colouration may be present. Males: fore femur with a pair of spines on proximal third ventrally, one spine in distal third, three spines distally, and one long seta dorsodistally; fore tibia without spine; palar claw broad, apex rounded ( Fig. 8A). Median lobe of sternite VII short and broad, with an angular apex and four long setae (Fig. 8C). Free lobe long, mesial angle obtuse, lateral angle square, with ca 20 long setae (Fig. 8D). Left paramere: shaft broad, fl attened, apex narrowly rounded; basal lobe sub-rectangular (Fig. 8F). Right paramere: shaft evenly curved, distal half parallel sided, apex rounded; pars stridens processus with ca 30 ridges (Fig. 8E).

Etymology
The species epithet refers to the shape of the left paramere's shaft, which resembles the blade of a knife.   Description COLOUR (Fig. 5E). Dorsum generally light orangish. Frons and vertex pale yellowish, eyes reddish brown. Pronotum light greyish brown. Hemelytron light orangish, without distinct mark. Suture between clavus and corium brownish, a band with minute red dots along anterior margin of clavus. Membrane translucent apically. Venter of thorax and abdomen, and legs brownish yellow.

Remarks
Micronecta cultellata sp. nov. is similar to M. drepani and M. erythra in the general form of the right paramere, with the evenly curved shaft, and in the shape of the free lobe. These three species can be separated from each other by the characteristics as follows. Micronecta erythra has a distinct colour pattern on the hemelytra and a distinct triangular projection on the lateral side of the left paramere. Micronecta drepani has dark marks on the hemelytra, but they do not form a distinct pattern. The left paramere of M. drepani has a short ridge running onto the lateral margin of the shaft, and the apex of the shaft is broad. Micronecta cultellata sp. nov. has a light orangish dorsum, without dark markings, and its left paramere lacks modifi cations on the lateral margin, with the apex narrow. The right paramere of M. drepani differs from that of M. erythra and M. cultellata sp. nov. by having a thicker, swollen basal part of the shaft (on the mesial side). This structure is not swollen in M. erythra and M. cultellata sp. nov., but gradually tapering to the distal part instead.  Figs 5F, 9A-E
Males: fore femur with two spines on distal third ventrally and a pair of spines distally; fore tibia without spines; palar claw broadened distally, apex rounded. Median lobe of sternite VII short, with four long setae and an angular apex (Fig. 9B). Free lobe slightly expanded posteriorly, mesial angle rounded, lateral angle square with ca 15 long setae (Fig. 9C). Left paramere: shaft broad, fl at, tapering towards rounded apex; basal lobe long, tongue-shaped (Fig. 9E). Right paramere: shaft parallel sided, strongly bent (at angle of nearly 90°) at distal fourth, then tapering towards narrowly rounded apex; base with a distinct hump on mesial side, near base of shaft (Fig. 9D).

Etymology
The species epithet 'arcuata' refers to the shape of the right paramere, which is slender and bent like a bow. Description COLOUR (Fig. 5G). Dorsum generally orangish-brownish yellow. Frons and vertex pale yellowish, eyes reddish brown. Pronotum yellowish brown, with one longitudinal yellow stripe on anterior part and two transverse yellow stripes on posterior part. Hemelytron with minute red dots scattered especially on hyaline anterior band of clavus, on boundary between corium and embolium. Corium with three obscure light brown markings at middle part. Membrane translucent and brownish. Venter of thorax and abdomen, and legs pale or light yellow. Males: fore femur with two spines on proximal third ventrally, one spine on distal third dorsally, one pair of spines distally, one long seta dorsodistally; fore tibia without spine; palar claw distally widened, apical margin rounded (Fig. 10A). Median lobe of sternite VII short, with acute apex and four long setae (Fig. 10C). Free lobe sub-rectangular, mesial angle rounded, lateral angle square, with ca 10 long setae, posterior margin slightly concave (Fig. 10D). Left paramere: shaft broad, fl at, distal part straight; apex narrowly rounded; basal lobe large, sub-rectangular (Fig. 10F). Right paramere: shaft parallel sided, strongly bent (at angle of nearly 90°) at distal fourth, apex rounded; pars stridens processus with ca 20 ridges (Fig. 10E).

Remarks
Among species of Micronecta occurring in Vietnam, four species, M. anatolica, M. arcuata sp. nov., M. fulvopicta sp. nov., and M. acuminata sp. nov., may be more closely related to each other, based on the general shapes of the prestrigilar fl ap (see Figs 9A, G, 10B, 11B), the median lobe of sternite VII (see Figs 9B, H, 10C, 11C), the free lobe (which is sub-rectangular, see Figs 9C, I, 10D, 11D), and the general form of the left and right parameres. In particular, the shaft of their right paramere is mostly parallel sided and straight at the proximal part, strongly bent at the distal fourth, and the apical part is simple, not distinctly broadened. The shaft of their right parameres is broad and fl at, with the lateral margin sinuate and without any projection; and the basal lobe of the right paramere is very large and broad.
All four species mentioned above, however, can be reliably separated from each other by the following characteristics.
In M. anatolica, the basal lobe of the left paramere is elongate and subovate, while that of other three species is broader and sub-rectangular. The base of the right paramere of M. anatolica has a distinct hump on the mesial margin near the beginning of the shaft, whereas this hump is less distinct in M. arcuata sp. nov., and absent in both M. fulvopicta sp. nov. and M. acuminata sp. nov. The apical part of the right paramere of M. anatolica is similar to that of M. fulvopicta sp. nov., which narrows towards the apex, while that of M. arcuata sp. nov. is more similar to that of M. acuminata sp. nov., which is slightly thickened before the apex.
Micronecta arcuata sp. nov. is distinct from the other three species in the form of the shaft of the left paramere, which is distinctly curved laterad. That of M. acuminata sp. nov. is also different, with an acuminate apical part. The form of the left paramere of M. acuminata sp. nov. is similar to that of M. acuta (Lundblad, 1933); however, the latter species lacks a strigil and its right paramere is clearly different (see Lundblad 1933b: fi g. 37e).
Besides structural charateristics, Micronecta fulvopicta sp. nov. has a distinct colour pattern on the dorsum, with strongly defi ned dark marks on the head, pronotum, and hemelytra (Fig. 5H). Its colour pattern is somewhat similar to that of M. vietnamica sp. nov., but the dark marks on the hemelytra of M. fulvopicta sp. nov. are broader than in the latter species. The structure of the parameres will also separate the two species (see also Remarks under M. vietnamica sp. nov.). Males: fore femur with two spines on proximal third ventrally, one spine in distal third dorsally, two spines distally, one pair of long setae dorsodistally; fore tibia without spine; palar claw petaloid, apex truncate (Fig. 12A). Median lobe of sternite VII with angular apex and four long setae (Fig. 12C). Free lobe long, parallel sided, mesial angle broadly rounded, lateral angle nearly square with ten long setae (Fig. 12D). Left paramere: shaft broad, fl at, proximal part curved, distal part nearly straight, apex rounded; basal lobe tongue-shaped (Fig. 12F). Right paramere: shaft slender and parallel sided proximally, distal third curved, apex narrowly rounded; pars stridens processus with ca 25 ridges (Fig. 12E).

Etymology
This new species is named after the country of the type locality. hyaline light yellowish. In most of specimens: clavus bordered with dark brown mark, becoming thicker on anterior margin; corium with two dark brown marks on middle part; a dark brown mark extending towards membrane; membrane generally transculent, brownish. Some specimens collected from Cao Bang and Phu Tho with variations in colour pattern of hemelytra. In some specimens from Phu Tho Prov. (Fig. 5K, at localities TS1510, TS1511): markings on hemelytra distinct but brighter overall, marks in middle part more fused into one large mark, and a dark mark (resembling inverted A-shape) just before membrane; membrane light coloured. In specimens from Cao Bang Prov. (Fig. 5L): markings on hemelytra indistinct, less contrasting against background colour of hemelytra; membrane light coloured. Venter of thorax and abdomen brownish yellow and legs pale yellow.

Remarks
This new species may be related to the group of M. anatolica, M. arcuata sp. nov., M. acuminata sp. nov., and M. fulvopicta sp. nov., as it also has the elongate sub-rectangular free lobe, the broad and fl at shaft of the left paramere, and the slender, distally curved shaft of the right paramere. It has strong dark pattern on the dorsum like M. fulvopicta sp. nov., but its dark marks are usually slenderer, and the patterns on the corium are different, sometimes indistinct (see Fig. 5L). The left paramere of M. vietnamica sp. nov. has a rather straight shaft and a trapezoid basal lobe, while in the four species mentioned above, the left paramere has a more sinuate lateral margin of the shaft and the basal lobe is either subovate or subrectangular. The right paramere of M. vietnamica sp. nov. is slenderer and strongly curved at the distal third, while that of the four species above is bent or curved at the distal fourth. In addition, the palar claw of M. vietnamica sp. nov. is much broader and has a different outline compared to that of M. anatolica, M. arcuata sp. nov., M. acuminata sp. nov., and M. fulvopicta sp. nov.  Figs 13A, 14A-D Nieser, Chen & Yang, 2005: 190, 197-200, fi gs 32-41 (type locality: Yunnan, China).

Diagnosis
Body length 1.7-1.8. Pronotum longer than median head length. Dorsum generally light brown. Hemelytron with small, irregular-shaped reddish marks, mostly on costal part; embolium with a longitudinal dark grey stripe and two brown patches (Fig. 13A).
Males: fore femur with two spines on middle third, a spine on distal third dorsally, and a pair of spines distally; fore tibia with three large and one small spine on distal third; palar claw distally widened, apical margin rounded. Median lobe of sternite VII narrow, with pointed apex and four long setae (Fig. 14A). Free lobe slightly expanded distally, mesial angle rounded, lateral angle slightly produced with ca 20 long setae, posterior margin nearly straight (Fig. 14B). Left paramere: shaft broad, fl at, with a deep notch along lateral margin near base, then followed by a triangular projection, distal part parallel sided, apex of paramere rounded; basal lobe longer than wide, sub-trapezoid (Fig. 14D). Right paramere: shaft slender proximally and club-shaped apically (Fig. 14C).

Distribution
China, Thailand Chen et al. 2006). First records for Vietnam.

Diagnosis
Body length 1.6-1.8. Pronotum longer than median head length. Dorsum generally brown. Hemelytron with brown markings, weakly contrasting with greyish background.
Males: fore femur with two stout spines on middle part; tibia without spine; palar claw widened distally, apex rounded. Median lobe of sternite VII narrow, with four long setae and a pointed apex. Free lobe expanded distally, mesial angle produced and rounded, posterior margin concave. Left paramere: shaft broad, fl at, with a triangular projection nearer to base, distal part parallel sided, apex of paramere rounded; basal lobe large, tongue-shaped. Right paramere: shaft slender proximally and pre-apically with a small notch in upper margin, apical part widened, fl ap-like (based on description by Wróblewski 1967: fi gs 1-5).

Material examined
No material available.

Distribution
Currently only known from Vietnam, and possibly endemic to the country. Records from Vietnam: Ninh Binh (Cuc Phuong), Nghe An, Ha Tinh .

Remarks
This species was reported from various localities in Vietnam, and we conducted samplings in some of those areas. Unfortunately, we have not yet obtained any fresh specimens of M. pocsi. This suggests that it is a rare species. If encountered, this species can easily be recognised by the unique structure of the right paramere (see Wróblewski 1967: fi g. 1). See also Remarks under M. clavata sp. nov. Nieser, Chen, Leksawasdi, Thanyakam & Duangsupa, 2004Figs 13B, 14E-G Micronecta tuwanoni Nieser, Chen, Leksawasdi, Thanyakam & Duangsupa, 2004, fi gs 2, 12-21 (type locality: Chiang Rai, Thailand).
Males: fore femur with two spines on proximal third, two spines on distal third, and one pair of spines distally; tibia with one spine in proximal third and a pair of spines distally; palar claw moderately widened distally, apex rounded. Median lobe of sternite VII with pointed apex and four long setae. Free lobe sub-rectangular, mesial angle rounded, lateral angle nearly square with ca 35 long setae, posterior margin slightly concave (Fig. 14E). Left paramere: shaft broad, fl at, with a triangular projection in the middle of lateral margin, distal part parallel sided, apex rounded; basal lobe longer than wide, subtrapezoid (Fig. 14G). Right paramere: shaft slender and parallel sided, curved near base and abruptly bent at distal fourth, apex narrowly rounded (Fig. 14F).

Distribution
Thailand . First record for Vietnam.

Remarks
Nieser et al. (2004)  Males: fore femur with two spines on proximal third ventrally, one spine on distal third dorsally, one pair of spines distally, and one long seta dorsodistally; fore tibia without spine; palar claw moderately widened distally, apex rounded (Fig. 15A). Median lobe of sternite VII with angular apex and three or four long setae (Fig. 15C). Free lobe sub-rectangular, mesial angle rounded, lateral angle nearly square, with ca 10 long setae, posterior margin straight (Fig. 15D). Left paramere: shaft broad, fl at, with a triangular projection in the middle of lateral margin, distal part tapering towards rounded apex; basal lobe large, sub-rectangular (Fig. 15F). Right paramere: shaft slender and parallel sided proximally, distal fourth curved, club-shaped with a truncate tip; pars stridens processus with about 20 ridges (Fig. 15E).

Etymology
The species epithet refers to the club-shaped apex of the right paramere.

Remarks
Among species of Micronecta occurring in Vietnam, four species, namely M. ornitheia, M. pocsi, M. tuwanoni, and M. clavata sp. nov., are most similar to each other, in having a triangular projection on the margin of the shaft of the left paramere. This structure is also present in the left paramere of M. erythra. However, the right paramere of M. erythra is evenly curved throughout the length of its shaft, while that of four species above is nearly straight or only curved near the base of the shaft.
The key structure which can help to reliably separate M. ornitheia, M. pocsi, M. tuwanoni, and M. clavata sp. nov. from each other is the apical part of the right paramere. In M. ornitheia, it is widened, with a small tip making it resemble a bird head. In M. pocsi, it is fl ap-like, with a small notch on the upper margin before apical part. In M. tuwanoni, the shaft of the right paramere is bent at the distal fourth and the apical part is not widened but tapering towards its tip. In M. clavata sp. nov., it is club-shaped and its tip is more truncate, not modifi ed.
The left paramere of these four species also has diagnostic features. In M. ornitheia, the triangular projection is situated near to the base of the shaft, and there is a distinct notch basally to the projection; and the basal lobe is longer than wide, and sub-trapezoid. In M. pocsi, the triangular projection is also nearer to the base of shaft, but there is no notch on the lateral margin; and the basal lobe is sub-triangular. In M. tuwanoni, the triangular projection arises on the proximal third (thus nearer to the base) of the shaft, and the basal lobe is trapezoid. In M. clavata sp. nov., the triangular projection is near to the middle part of the lateral margin of the shaft, and the basal lobe is sub-rectangular. Males: fore femur with a pair of spines on middle third, one spine in distal third dorsally, and two spines distally; fore tibia without spine; palar claw moderately widened distally, apex rounded (Fig. 16A). Median lobe of sternite VII with angular, acute apex and four long setae (Fig. 16C). Free lobe short, distally widened, both angles nearly square, lateral with ca 25 long setae, mostly on lateral margin (Fig. 16D). Left paramere: shaft broad, fl at, tapering towards a slightly swollen, rounded apex, and with a small process near apex; basal lobe longer than wide, sub-rectangular (Fig. 16F). Right paramere: distal part of shaft widened and folded into a gutter-like structure, with a lobe on one side, apex narrowly rounded; base with a distinct hump on mesial side, near base of shaft; pars stridens processus with ca 20 ridges (Fig. 16E).

Etymology
The species epithet refers to the sinuate and folded tip of the right paramere. Description COLOUR (Fig. 13E). Dorsum generally sordid brown. Frons and vertex light yellowish, eyes dark brown. Pronotum sordid brown, with a yellowish longitudinal stripe on anterior part and two yellowish transverse stripes on posterior part, stripes usually indistinct. Hemelytron generally brownish, embolium hyaline, with brown mark along suture with corium. Membrane translucent. Venter of thorax and abdomen brownish yellow, legs pale greyish yellow.

Remarks
This new species appears most similar to M. prashadana  from Sri Lanka, in the general form of the parameres, the outline of palar claw, and the shape of the free lobe. In both species, the right paramere has a beak-like apical part, and the left paramere has a swollen, rounded apex. However, there are substantial differences between the two species. In M. sinuata sp. nov., the left paramere has its shaft gently tapering towards a slightly swollen, rounded apex; the basal lobe of the left paramere is well developed and sub-rectangular; the right paramere has a pre-apical lobe on the mesial side of the shaft, and the base of the right paramere has a distinct hump on its mesial side, near the base of shaft. In M. prashadana, the shaft of the left paramere is swollen on the basal part, and its apex more swollen and larger; the basal lobe of the left paramere is less developed, much narrower and subovate; the right paramere has a pre-apical lobe on the lateral side of shaft; and the base of the right paramere has no hump.
Among species of Micronecta occurring in Vietnam, M. sinuata sp. nov. has a rather unique structure of both parameres, with no other species having a similar structure.
Males: fore femur with two spines on middle third, one or two spines distally, and no long seta dorsodistally; fore tibia with one small spine on proximal third dorsally, and three spines on distal third; palar claw distally moderately widened, apex rounded (Fig. 17A). Median lobe of sternite VII with narrow, pointed apex and four long setae (Fig. 17C). Free lobe short, distally widened and wavy, both angles nearly square, without long setae; posterior margin strongly sinuate (Fig. 17D). Left paramere: shaft relatively short and broad, apex truncate, with two ridges running to lateral margin, thus forming two triangular projections on lateral margin; basal lobe longer than wide, sub-rectangular (Fig. 17F). Right paramere: shaft parallel sided, slightly curved at proximal part, abruptly constricted at distal third, apical part wavy and lobate; pars stridens processus with 18-27 ridges (Fig. 17E).

Etymology
The species epithet refers to the wavy, undulating free lobe. Description COLOUR (Fig. 13F). Dorsum generally brownish grey. Frons and vertex pale yellowish, eyes blackish brown. Pronotum greyish brown. Hemelytron with greyish background. Clavus with brown punctures near anterior margin. Corium with a broad transverse dark brown mark in the middle. Membrane generally dark brown, more hyaline apically. Venter of thorax and abdomen greyish brown and legs pale yellow or nearly whitish. Males: fore femur with one pair of spines on proximal third ventrally, one longer spine on distal third dorsally, two spines distally, and one long seta dorsodistally; fore tibia with two long spines on distal third ventrally; palar claw distally moderately widened, apex rounded (Fig. 18A). Median lobe of sternite VII with three or four long setae and an angular apex (Fig. 18C). Free lobe short, distally strongly widened, posterior margin straight, lateral corner broadly notched, with a row of uniformly short, dark coloured setae restricted to lateral angle (Fig. 18D). Left paramere: shaft relatively short and broad, with two ridges running to lateral margin, with the proximal ridge forming a triangular projection on lateral margin; mesial margin sinuate distally; apex tongue-shaped; basal lobe sub-triangular, directed towards paramere's apex (Fig. 18F). Right paramere: shaft with sinuate sides, abruptly constricted and bent at the middle part, apical part wavy and lobate (Fig. 18E); pars stridens processus with ca 25 ridges.

Etymology
This species is named after Dr Nico Nieser in honour of his great contributions to the taxonomy and our knowledge of Micronectidae.

Etymology
This species is dedicated to Dr Chen Ping-ping, for her signifi cant contributions to the taxonomy and our knowledge of Micronectidae.

Material examined
Holotype VIETNAM • ♂; Nghe An Prov., Ky Son, Nat' road 7, Ta Ca commune, Loi stream;16 Apr. 2013;A.D. Tran et al. leg  Description COLOUR (Fig. 13I-J). With variations in colour of dorsum and pattern of hemelytra (a dark form and a pale form). Dark form (specimens from site TAD1380, Cao Bang Prov. and TAD1301, Nghe An Prov.) with dorsum generally light brown (Fig. 13I): frons and vertex brownish yellow to brown; eyes reddish brown. Pronotum pale yellowish brown. Hemelytron with minute red dots scattered especially on orangish band along anterior margin of clavus, and on boundary between corium and embolium. Corium with three brown marks in middle part, usually fused into one irregular-shaped mark. Right membrane with similar colour and texture to corium, more translucent apically. Left membrane translucent and brown. Venter of thorax and abdomen pale yellow to yellowish brown, and legs very light pale yellow or nearly whitish. Pale form (specimens at site TAD1301, Nghe An Prov.) (Fig. 13J): frons, vertex, and pronotum pale yellowish. Hemelytron with indistinct marks, more like scattered small orangish dots. Membrane with similar colour and texture to corium, more translucent apically. Venter of thorax and abdomen pale yellow, and legs very light pale yellow or nearly whitish.  (Fig. 19B). Strigil present. Median lobe of sternite VII, free lobe, and parameres as in diagnosis.

Remarks
Three new species, M. undulata sp. nov., M. nieseri sp. nov., and M. pingae sp. nov., are apparently related to each other and to M. janssoni  from Yunnan (China) by having the left paramere with transverse ridge(s) or grooves on its shaft, a strongly modifi ed apical part of the right paramere, and by the outline of the palar claw.
Among these four species, M. undulata sp. nov. is most similar to M. janssoni in the general outline of the prestrigilar fl ap on segment V, the shape of the median lobe of sternite VII, the broad truncate apex of the left paramere, and the shape of the basal lobe of the left paramere. The characteristics which separate these two species include the structure of the free lobe, the ridges on the left paramere, and the shape of the apical part of the right paramere. In M. undulata sp. nov., the free lobe is wavy distally, and without long setae, while in M. janssoni, it is only slightly sinuate at the apical margin and with long setae on the lateral angle. The left paramere of M. undulata sp. nov. has two transverse ridges on its shaft, one near the base, and one near the apex, while that of M. janssoni has one transverse ridge near the base of shaft and three less distinct grooves on the distal third of the shaft. The apical part of the right paramere is also differently modifi ed in these two species (compare Fig. 17E with Nieser et al. 2005: fi g. 16).
In a parallel manner, M. nieseri sp. nov. is most similar to M. pingae sp. nov. in the general outline of the prestrigilar fl ap on segment V, the shape of the basal lobe of the left paramere, the notch on the lateral margin near the base of the left paramere shaft, and the sinuate mesial margin of the left paramere. They can easily be separated from each other by the following characteristics. In M. nieseri sp. nov., the median lobe of sternite VII has an angular apex; the free lobe has a broadly notched lateral corner; and the left paramere has two transverse ridges, one near the basal notch and one near to the tounge-like apex. In M. pingae sp. nov., the median lobe of sternite VII is narrowly rounded; the free lobe has both lateral and mesial corners broadly notched; and the left paramere has only one transverse ridge pre-apically which runs into a triangular projection and has a truncate apex. The apical part of the right paramere of M. nieseri sp. nov. and M. pingae sp. nov. are both strongly modifi ed, but differently, with that of M. nieseri sp. nov. being more elongate, and that of M. pingae sp. nov., by contrast, being shorter and broader, with a more acuminate tip. Both M. nieseri sp. nov. and M. pingae sp. nov. have various colour forms, with both having a paler form in which the hemelytra generally are pale yellow and without distinct markings. Horváth, 1904 Figs 13K, 20 Material examined

Distribution
Vietnam: Hanoi, Quang Ninh, Ha Tinh ; fi rst records for Ninh Binh and southern provinces of Vietnam. Other countries: widespread from India and Sri Lanka through Southeast Asian mainland to Sumatra, Java, and Bali .

Remarks
Micronecta haliploides can immediately be recognised by the distinct dark spots scattered on the hemelytra. In this species the knob-like apex of the left paramere is also unique within Micronecta.   Breddin, 1905 (ZVNU). G. M. tarsalis Chen, 1960 (ZVNU). H. S. issa  (ZVNU). All to the same scale.

Distribution
Sri Lanka, India, East Pakistan, Thailand, Hong Kong, Vietnam .  clearly indicated that the holotype and paratypes of M. altera were all from Sri Lanka, and noted that he had seen examples of this species from India, Pakistan, Thailand, Hong Kong, and Vietnam, but without providing specifi c locality data. However, subsequent studies by various heteropterists did not provide any additional reports of this species from Southeast Asia again. , when producing his key to Southeast Asian Micronecta, apparently overlooked M. altera and did not include it. Based on numerous samples as above, we now confi rm the occurrence of this species in Vietnam. Among subsequent studies dealing with M. quadistrigata and another closely related species, M. kymatista Nieser & Chen, 1999, only Nieser & Chen (1999 made a brief comparative reference to M. altera. Tinerella (2008Tinerella ( , 2013) also commented on this species, questioning the potential conspecifi city between M. quadristrigata, M. altera, and M. kymatista.

Remarks
As  previously noted, there are a few differences between M. quadristrigata and M. altera, including the body length (M. altera is slightly larger than M. quadristrigta), the fore tibia and pala (M. altera has larger ones), the shape of the palar claw (M. altera has a small notch in the middle), the shaft of the right paramere (that of M. altera is longer, clearly thicker on the basal half, then gradually tapering on the apical half, while that of M. quadristrigata is mostly parallel sided and only tapering on the apical fi fth), and the curvature between the base and the shaft of the left paramere, opposite the basal lobe (which is about 90° in M. altera, and is clearly greater than 90° in M. quadristrigata) (compare Fig. 22B, F). Our samples help to confi rm the observation by  that M. quadristrigata and M. altera are separate species, and that the detailed structures of the parameres provide reliable characters. It is notable that the body lengths of M. quadristrigata and M. altera, as provided by Wróblewski (1972a:  table 1), had overlapping ranges, although that of M. altera fell into the larger range. Based on such comparative morphological features, it seems that illustrations of specimens of M. quadristrigata in Chen et al. (2015) belong to M. altera instead. However, we do not have access to these specimens to confi rm this speculation. Among three species of the subgenus Sigmonecta, M. kymatista Nieser & Chen, 1999 is most similar to M. quadristrigata in the appearance of parameres. For comparison between these two species, see Nieser & Chen (1999: 83). Micronecta khasiensis Hutchinson, 1940

Material examined
No material available.
Males: pala with a secondary claw; primary palar claw widened distally, apex rounded. Median lobe of sternite VII short and broad, with an angular apex. Free lobe subparallel sided, with mesial angle rounded, posterior margin nearly straight, lateral angle well-produced, ca 16-23 long setae on lateral side of free lobe (Fig. 23E). Left paramere: shaft styliform, tapering towards narrowly rounded apex, apical part slightly twisted; basal lobe relatively short and broad (Fig. 23G). Right paramere: base of shaft with a distinct swelling, proximal part subparallel sided, from distal fourth tapering towards narrowly rounded apex (Fig. 23F).

Distribution
Vietnam: Dong Nai (Cat Tien) . The records by Tran et al. (2014) from Phu Tho Prov. were a misidentifi cation. After a re-examination, we determine them as M. melanochroa. Other countries: Thailand, Singapore , and Cambodia (Polhemus 2017).

Remarks
Three species, M. polhemusi, M. khasiensis, and M. melanochroa, may easily be confused because of their dark dorsum and their similar parameres. Detailed structures of the parameres and primary palar claw, however, provide reliable characters for separating them. The base of right paramere shaft of M. polhemusi has a large swelling, which is indistinct or absent in the other two species. Micronecta khasiensis can be separated from M. melanochroa by the male primary palar claw and detailed structures of the parameres. The primary palar claw of M. khasiensis is narrow and parallel sided, while that of M. melanochroa is broader and strongly widened apically. The primary palar claw of M. pohemusi is club-shaped, and moderately widened apically. The left paramere of M. khasiensis is slightly expanded before the narrowly rounded apex, while that of M. melanochroa has a slightly twisted apical part. The right paramere of M. khasiensis has a pointed apex, while that of M. melanochroa has a blunt apex.

Etymology
The species epithet refers to the wrinkles on the left paramere.

Diagnosis
Body length 1.8-2.2. Pronotum longer than median head length. Dorsum generally light brown. Hemelytron with four broken longitudinal stripes, usually confl uent posteriorly; embolium with three brown patches, usually fused into a longitudinal stripe (Fig. 21F).
Males: palar claw parallel sided, broadly curved, with a notch before apex; apex pointed ( Fig. 25A). Median lobe of sternite VII triangular with rounded apex and one long setae. Free lobe widened distally, mesial angle obtuse, posterior margin convex, lateral angle nearly square, with ca 10 long setae on lateral side (Fig. 25B). Left paramere: shaft styliform, relatively stout, with distal part dark brown, apex blunt; basal lobe short and subovate (Fig. 25D). Right paramere: shaft with proximal part parallel sided and nearly straight, distal third evenly curved and tapering towards pointed apex (Fig. 25C).

Remarks
The illustration of the parameres of M. fugitans from Peninsular Malaysia by Wróblewski (1968) appears different from those of M. fugitans illustrated by . Wróblewski (1968) also noted these differences. We think that the specimens studied by Wróblewski (1968) may belong to another species, not M. fugitans. Our samples from Vietnam perfectly match the illustration of M. fugitans by . The dark distal part of the shaft of the left paramere, and the shape of the palar claw are important diagnostic characterstics for determining this species. Note that the shape of its right paramere is very similar to that of M. tarsalis, but this is the only similarity between the two species. Figs 21G, 25E-H Micronecta tarsalis Chen, 1960: 114, fi gs 1-5, 12-13 (type locality: Sri Lanka).  [not assigned to any subgenus] M. fugitans  [not assigned to any subgenus] M. tarsalis  [not assigned to any subgenus] Synaptonecta Lundblad 1933 Synaptonecta issa

Discussion
With regard to our knowledge of the Asian fauna of Micronectidae, recent regional taxonomic reviews have covered only some parts, e.g., southwestern China (Yunnan), Borneo, New Guinea Tinerella 2008;Chen et al. 2015). The fauna of Southeast Asian mainland remains poorly studied, and there is still a big gap in our knowledge.  provided a key to 24 species of Micronectidae from Southeast Asia, but his study emphasised the Thai fauna. Subsequently, Nieser et al. (2004) described two more species of Micronecta from Thailand.  reviewed the Micronectidae from Peninsular Malaysia and Singapore, reporting 20 species, of which 19 belong to Micronecta. However, there is a lack of comprehensive data from the remaining Southeast Asian countries, e.g., Laos, Cambodia, and Myanmar. Very little is known about the micronectid fauna in these countries. Concerning the micronectid fauna of Vietnam, prior to the present study, 16 species, including 15 species of Micronecta and one of Synaptonecta, were reported, largely thanks to the works by Wróblewski from 1962Wróblewski from to 1972. However, the studies by Wróblewski during that period were based on sporadic samples.
The present study has signifi cantly raised the number of micronectid species known from Vietnam to 37, by reporting eleven species as new to science and nine as fi rst records for the country, all of Micronecta. Thus, the results from the present study have partially fi lled in the gap of knowledge of the regional micronectid fauna. Although the discoveries of new species or new records are normal for insects, such a high number of new species found from Vietnam is rather surprising. This is probably due to the cumulative collections of Micronectidae made throughout Vietnam over the past 20 years. Micronectid species are known to have strong fl ying ability, meaning they possess a high dispersal capability, and many micronectid species are known to have wide ranges of distribution. Thus, the eleven new species reported here probably occur not only in Vietnam, but also in surrounding areas. The nine species reported as fi rst records for Vietnam support this hypothesis. Therefore, the fi ndings also suggest that a more comprehensive study based on extensive collections throughout the Southeast Asian mainland is required for a better understanding of the regional fauna and overall diversity of Micronectidae.
Another point to consider for future studies is the subgeneric classifi cation of Micronecta, which remains a challenging task (see also Remarks section on Micronecta). This is due to the incomplete knowledge of the species diversity of Micronecta and the lack of intrageneric phylogenetic analyses. Recent regional taxonomic reviews of Micronectidae, and Micronecta in particular Nieser et al. 2005;Tinerella 2008Tinerella , 2013Chen et al. 2015), have made some contributions towards this task. Tinerella (2008Tinerella ( , 2013 attempted to reconstruct phylogenetic relationships among Australasian micronectid genera based on morphological data, but the intrageneric relationship of Micronecta was not a focus in his studies. Therefore, a taxonomic review that covers major geographic areas of distribution of Micronecta and comprehensive phylogenetic analyses with an adequate taxon sampling and relevant morphological and DNA evidence are still much needed.