Revision of the Oriental genus Idiotrephes (Heteroptera: Nepomorpha: Helotrephidae)

The Oriental helotrephid genus Idiotrephes Lundblad, 1933, is taxonomically revised. Species discrimination is based on male genitalia and female terminalia. Three species groups are recognized. The I. chinai group contains I. chinai Lundblad, 1933 (type species; from Sumatra, Borneo, and West Malaysia) and three newly described species; I. asiaticus sp. n. (from Vietnam, Thai­ land, and west Malaysia); I.yupae sp. n., and I. polhemusi sp. n. (both from Thailand). The I. maior group contains I. maior Papacek, 1994; I. meszarosi Papacek, 1995 (both from Vietnam), and I. hainanensis sp. n. (from Hainan, China). The I. thai group consists of two newly described species from north and northeast Thailand, I. thai sp. n. and I. shepardi sp. n. In addition, some features of biology and morphology of the ovipositor are also included.


INTRODUCTION
Although Idiotrephes species are relatively common and abundant in southeast Asia, the genus Idiotrephes was described by Lundblad (1933) based on material of only a single new species, I. chinai Lundblad, 1933, from Sumatra.More than sixty years later, Papacek (1994,1995) described two further species, I. maior and I. meszarosi, from Vietnam.Records of I. chinai from Vietnam (Papacek, 1994) and Thailand (Zettel, 1995) refer to a sibling species, described here as new, I. asiaticus.Zettel (1997b) figured the types of I. chinai and recorded this species from Sarawak, Borneo; Kovac & Yang (1990) also recorded this species from peninsular Malaysia.To clarify the situation between these two sibling species, and to describe further new species from the collection of the Natural History Museum Vienna and some private collections, a complete taxonomic revision of the genus became necessary.
Idiotrephes is presently included within the tribus Limnotrephini Polhemus, 1990, of the subfamily Helotrephinae (Polhemus, 1990).Recently, Zettel (1997a) discussed the doubtful monophyly of this tribe in the pre sent phylogenetic system.The genus Idiotrephes is very well defined by some important autapomorphies, as indi cated in the generic diagnosis below.It is easily dist-iguished from other genera of its distribution area with the key of Zettel (1998).

MATERIAL AND METHODS
Dry card-mounted specimens as well as material preserved in 70% ethanol were studied.Male and female terminalia were both dry-prepared and mounted on slides for examination of morphology and for measurements**.
Measurements and scales in figures of all the structural parts are in millimeters (mm).Morphometrical characters measured in male and female genitalia are defined in Figs 1-3 and their legends.Numbers of specimens, males and females, and their structures measured in individual species are variable depending on their availability (see paragraphs "Material examined").For this reason separate data for different morphs and sexes as well as statistical data are not presented in tables but only as ranges of measurements.Figures of terminalia represent ventral view.
Terminology used here is derived mainly from Papacek et al. (1988,1989).Abbreviations in the text are as follows: brach.specimenwith brachypterous forewing; macr.-specimen with macropterous forewing; other abbreviations are presented in the next section, and in Figs 1-4 and 62. Data about material exam ined are presented here as given on the labels in the specimens' depositories.
Diagnosis.Small (1.30-1.78mm) Limnotrephini (sensu Polhemus, 1990) with semiglobular appearance; colour yellowish, dorsally with scattered, usually small, dark spots of varying size and number, usually more dis tinct in macropterous specimens; on head more confluent than on pronotum, mesoscutellum, and hemelytra; lateral carina of cephalonotum not continuous across eye, but indenting it conspicuously in the posterior part (Fig. 4), without distinct differences between morphs; in dorsal view of total insect cephalonotum distinctly shorter than posterior part of body; cephalonotum and mesoscutellum shining, without or with very sparse and fine or shallow spots, that on head not correlated with colour pattern, on thorax and hemelytra much smaller than dark spot with same distribution; hemelytra with coarser punctation and sparse, but quite long hairs; antenna two-segmented in both morphs; rostrum short, stout, reaching approxi mately posterior corner of prosternal carina; tarsal for mula (number of tarsal segments on fore-, middle -, and hind leg) 1-1-2; propleural plate at inner corner rounded (Fig. 4); prosternal, mesosternal, metasternal carinae sim ple; abdominal carinae on sternum 2 and 3 high, on sternum 4 very low or lacking*; sterna 4-6 medially fused, with sutures more or less reduced.
Larvae not strongly flattened.
The asymmetrical female abdominal sternum 7 with a dextrocaudal incision or impression and a dextrocaudal break, the club-shaped apex of aedeagus, and a very char acteristic shape of male left paramere, are autapomorphies of Idiotrephes.
Wing polymorphism.Papácek (1995) found three dif ferent types of pterygopolymorphism in Idiotrephes spe cies: (a) fore and hind wing macropterous [in I. "chinai" (= asiaticus sp.n.)];(b) forewing brachypterous and hind wing micropterous; (c) forewing and hind wing brachy pterous (in I. maior).The macropterous morph (a) is easily recognized by the presence of a claval suture and a separated embolium on the hemelytron.The other morphs (b, c) are distinguishable only by hindwings, and combi nation (b) is most common in Helotrephidae, whereas the frequency of macropterous morphs (a) differs between species, obviously depending on their habitat preferences (see, e.g., Zettel, 1999).Brachypterous hind wings (c) have so far been rarely observed in Helotrephidae (see Papácek et al., 1989).
Most Idiotrephes species were collected in often small stagnant waters (see below).The consequent necessity to migrate, if the water body dries up, is expressed by a rela tively high rate of macropterous morphs compared with rates in most other helotrephid genera.
Species discrimination.The relatively minute Idiotre phes species are very uniform in their external appearance.They are not readily distinguishable from each other by characters of cephalonotum, pterothorax, basal abdominal part, or by size.The colour pattern varies slightly within some species, but does not serve to distin guish species.Size varies considerably within species, as females and macropterous morphs are larger than males and hind-wing-brachypterous morphs.For example, the * Polhemus (1990) and Zettel (1998) state that the sternal carinae reach sternum 5, because the very low carina of sternum 4 appears sometimes (especially in males) longer than sternum 4. The suture between sterna 4 and 5 is not present medially, and there is no interruption of the carina, which would indicate its presence on sternum 5.
Figs 5-17: Idiotrephes chinai, variability of male genitalia.5-7 -lectotype; 8-10 -specimen from Sarawak; 11-13specimens from Singapore; 14-17 -specimens from west Malaysia (Selangor, Ulu Gombag).5, 8, 11, 14, 17 -aedeagus, b, c, respectively -shapes of tips of aedeagi (the same lettering used in the following figures); 14c -somewhat aberant shape; 17 -aedeagus with broken tip (after mating?); 6, 9, 12, 15 -left paramere; 7, 10, 13, 16 -right paramere (different alternative aberrant shapes).Scale bar: 0.2 mm (0.1 mm for Figs 5b, 8b, 11b, 14b, c).body lengths of different specimens of the same species can differ by 6-20% (see Tables 1-3).However, if the same morphs and sexes of the same sympatric population are compared, species differ constantly.The intensity of punctation of the dorsal surface serves also as a weak character for species discrimination, but here also the dif ferences between morphs are often stronger than between species.Also, the ventral carinae are relatively uniform in all species, but some may be recognized by special char acteristics (e.g., I. thai sp.n. by the more ventrad-pointing apex of the metasternal carina).Reliable species identifi cation is based on the examination of male genitalia, which also bear the main characters for distinguishing the three species groups.At the apex of the aedeagus, only two species show some intraspecific variability between specimens or local populations, I. chinai and I. asiaticus.The apices of the right paramere and several characters of the left paramere are very constant within species, and can be used to distinguish some species with certainty.The female abdominal sternum 7 (= subgenital plate) and first valvulae of ovipositor serve best to distinguish females.Only a few species (e.g., I. chinai and I. asiati cus; the species of the I. maior group) have such similar abdominal sterna 7 that identification of females should be confirmed by the first valvulae of females, and by examination of males from the same sampling.The rela tive morphometrical parameters of the tip of the aedeagus and the first valvulae (see Figs 1-3) can be used as addi tional differential characters.
Biology and habitats.The life cycle, nutrition, and most other aspects of the biology of Idiotrephes are known only in I. asiaticus * (cf. Papacek, 1993), and this knowledge is limited.I. asiaticus is with high probability a bivoltine species.The females lay eggs in small groups (2-4 eggs/group) on the surface of different objects in the water (rocky bottom, stones, gravel, plants, artificial objects).The ovipositional period lasts more than one month and starts immediately after mating.Preimaginal development lasts about two months; individual stadia are 10-17 days.Idiotrephes asiaticus is a predaceous water bug that attacks a large spectrum of prey (e. g., small dipteran, ephemeran or heteropteran larvae, cladocerans, copepods, annelids, rotifers, and protozoans).The last two instars as well as adults feed also on earlier instars.No prey preference was found.Rather, size seems to be the most important feature in the choice of prey and the attack.
Idiotrephes species were found in a variety of habitats.Unlike Distotrephes species, they are never found in lotic areas of streams, but in lentic places or stagnant waters.Lentic bays of streams and rivers, as well as small pools on the banks of streams, are preferred habitats.Artificial stagnant waters are also inhabited by some species, although in southeast Asia these habitats are usually dominated by Tiphotrephes indicus (Distant, 1910).Idi otrephes species can live under extreme and changing environmental conditions (temperature, velocity of flow, turbidity, dry and wet seasons, prey availability), espe cially in ephemeral water bodies as lithotelms on the rocky bottom of rivers or streams in the monsoonal area.Thus they are not only eurytopic but also very plastic and stress-tolerant.More information on habitats are given after the description of each species.
Distribution.Southeast Asian mainland, Hainan, Sumatra, Borneo; limited to the east by Wallace's Line (sensu Dickerson et al., 1928), and unknown from Java and Palawan so far.The highest diversification of the genus is in Indochina and in northern parts of Thailand.The distribution of individual spe cies of the genus Idiotrephes is presented in Fig. 71.

The Idiotrephes chinai group
The Idiotrephes chinai group is a complex of several closely related, partly allopatric, partly sympatric species, and intraspecifically varying local populations.The authors are aware that the present study on this groupbased on classical morphology only -is a preliminary one.The group as a whole is well defined.Common char acters of the species are: (1) distal part of the aedeagus  . polhemusi).Differences between species are mainly found in the shape of the incision of the female sternum 7, in the tip of the aedeagus, and in certain characters of both parameres.Idiotrephes chinai is distributed in Sumatra, Borneo, Singapore, and the southern part of peninsular Malaysia; there are small dif ferences among specimens of these island and mainland populations, but we lack enough material to decide if these differences are constant.Idiotrephes asiaticus is widely distributed in west Malaysia, Thailand, and Viet nam; small differences are found nearly among all popu lations studied; the tendency of prolongation of the aedeagus tip from north Vietnam westwards and south wards was observed.Idiotrephes asiaticus shows a higher variation of male genitalia than any other helotrephid spe cies.Within the supposed distribution area of I. asiaticus, two further species can be distinguished by much more obvious differences; both are known only from single localities in Thailand.In Idiotrephes chinai and I. asi aticus the tip of the mesosternal carina is directed anteriad (Fig. 63), and the first left valvifer has a conspicuous laterocaudal lobe.
Female: Incision of the abdominal sternum 7 simple (Fig. 30a, b), in some populations or specimens with light U-shaped impression anteriorly from incision (Fig. 30c).Right anterolateral margin of abdominal sternum 7 with conspicuous lobe (Figs 30a, b, c).First valvulae small, uniform in all populations and female specimens, with rounded margins of its caudal corners.Posterocaudal lobe of the first left valvifer with conspicuous lobe (Fig. 54).
Table 1.Some morphometrical characters of males of I. chinai.a/b -ratio: length of apical club-shaped process of aedeagus/width of the same structure (see also Fig. 1); angle 8 -angle between longitudinal axis of the club-shaped process and lon gitudinal axis of the subapical narrowed part of aedeagus (see also Fig. 2).
Comparative notes.Similar to I. chinai, but aedeagus with shorter tip and larger angle 8; first valvulae larger than in I. chinai, posterior corner of first valvulae pro duced in I. asiaticus, rounded in I. chinai (compare Figs 54,55).
Etymology.Named after its distribution over a large area of mainland of southeast Asia.
Habitats.Idiotrephes asiaticus sp.n. is a eurytopic species, which can be found in a wide variety of stagnant and lentic waters.It is known from small lithotelms, some less than a half meter in diameter, in Chiang Mai Province (leg.Zettel, no. 2) and Nam Cat Tien N. P. in Dong Nai Province (leg.Papácek); from seeping rocks in Khlong Lan, Namla waterfall (leg.Kovac); from the edges of lentic areas of a small stream in Phetchabun Province (leg.Zettel, no.22); from the lentic sides of a large river in Khon Kaen Province (leg.Zettel,no. 19); from a very shallow, nearly stagnant stream, whose bottom is covered with algae in Khon Kaen (no.20a, b); from concrete water tanks in the Khon Kaen University campus (leg.Shepard); and also from bonsai ceramic bowls in Hanoi, Vietnam (leg.Papácek).
Diagnosis.Body length rather variable compared with other Idiotrephes spp.(see Table 3); prosternal carina with two obtuse tips, each more or less quadrangular; tip of mesosternal carina oriented posteriad (Fig. 64).
Female: Abdominal sternum 7 with simple deep roundly subtrapezoidal incision and large J-shaped impression with break-lined margin (Fig. 32); two groups of thick bristles on surface of this incision.Complex of first valvifers and valvulae relatively large (Fig. 56) (see also relative morphometrical characters in Table 3).First left valvula with conspicuous posteriad pointing produced caudal corner, first right valvula only with roundly obtuse caudal corner.
Comparative notes.Close to I. asiaticus sp.n.Female abdominal sternum 7 somewhat similar to that of I. yupae sp.n., also with distinct long hair (bristles) tuft at bottom of impression, but with less distinct ridge.Tip of aedeagus longer than in I. asiaticus, less acute than in I. yupae.Left paramere not forming a right angle at end of base as in I. yupae, more similar to that of I. asiaticus, but with diagnostic preapical swelling.
Etymology.This species is named in honour of Dr. John T. Polhemus (Englewood, Colorado), outstanding heteropterist, to celebrate his 70th birthday.

Habitats.
No details on the habitats are known.
Female: Abdominal sternum 7 with large simple inci sion and impression lined anteromesally with con spicuous ridge (Figs 33 a, b).Two groups of thick bristles at bottom of impression.Complex of first valvifers and valvulae large.Lateroposterior margin of first right valvula with small inconspicuous wide lobe.
Comparative notes.Similar to I. asiaticus sp.n., but larger; female abdominal sternum 7 with more distinct break-like ridge and well developed obliquely directed tuft of hairs (bristles) at bottom of impression.Male aedeagus with more bent (dorsal outline of apex nearly rectangular to longitudinal axis of aedeagus) and more acute apex; differing from other I. chinai-group species by the larger angle 8. Left paramere basally stouter, and its shape also conspicuously different from that of I. pol hemusi.
Type material.Holotype (macr.k): "Thailand: Chiang Mai Prov.Doi Inthanon NP, Mae Klang, Falls 4.11.1995leg.H. Table 3.Comparison of some morphometrical characters of Idiotrephes spp.a/b -ratio: length of apical club-shaped process of aedeagus/width of the same structure (see also Fig. 1); angle 8 -angle between longitudinal axis of the club-shaped process and lon gitudinal axis of subapical narrowed part of aedeagus (see also Fig. 2); a/vl -ratio: length of apodeme of the first valvula/length of the first valvula; vl/vw -ratio: length of the first valvula/width of the same structure (see also Fig. 3).
Etymology.This species is named in honour of Prof. Yupa Hanboonsong (Khon Kaen University) for her help and hospi tality to the second author during his stay in Thailand and for her contributions to the knowledge of Thai insects.
Habitats.The type locality is a shallow, rather large inunda tion pool on the banks of the Mae Klang Waterfalls.Idiotrephes yupae sp.n. was also found in a small lithotelm and on the seeping rock in the Namla Waterfall.

The Idiotrephes maior group
The group contains three species, two from Vietnam and one from the zoogeographically closely related island of Hainan (south China).Important characters of the group are: (1) distal part of aedeagus (distal of opening) relatively short (compared to I. chinai group); (2) distal part of right paramere slender and tapered, apex acumi nate; (3) incision of female abdominal sternum 7 small; (4) break-like ridge of female abdominal sternum 7 com plete, usually strongly developed; (5) size medium to large (see Table 3).Differences among species are mainly found in the tip of the aedeagus and in the shape of the left paramere, small differences also occur in the female abdominal sternum 7, and complex of first valvulae and first valvifers.
Female: Abdominal sternum 7 with small incision and impression margined by L-shaped break-like ridge (Fig. 49).First valvifers large, broad; lateral margin of left val vifer posteriorly with small incision.Posterior corners of first valvulae in form small rounded lobes (Fig. 58).
Comparative notes.Idiotrephes maior clearly differs from other species of the I. maior-group by the tip of aedeagus and the shape of the first valvulae; from species of the I. chinai-group by the short apex of aedeagus, the incision of female abdominal sternum 7, and by the size and shape of the first valvifers and valvulae.L-shaped break-like ridge (Fig. 51).First valvulae very narrow (Fig. 60).
Comparative notes.Idiotrephes hainanensis differs distinctly from all other Idiotrephes species by the apex of the aedeagus (similar to aedeagus of I. meszarosi but apex laterally flattened in I. meszarosi, and evidently three-dimensional in I. hainanensis), and by the very narrow first valvulae of females.
Etymology.Named for the distribution in Hainan Island.Distribution.China: Hainan.Habitats.No information available.

The Idiotrephes thai group
The group presently contains two species, I. thai sp.n. and I. shepardi sp.n. from north and northeast Thailand, which are well characterized by the following characters: (1) tip of the aedeagus not elongate, apically rounded, and with a more or less developed tooth; (2) apex of the right paramere nearly transversely truncate or rounded; (3) distal part of left paramere very slender; (4) female abdominal sternum 7 without distinct incision, with weak shallow emargination only; (5) size relatively large (see Table 3).The two species are easy to separate by the male genitalia and the female abdominal sternum 7.
Female: Abdominal sternum 7 with small posteriorly directed tip of hind margin, and impression lined by J-shaped break-like ridge in some specimens (Figs 52a, b) or without ridge (Fig. 52c).First valvifers and valvulae relatively narrow but robust (Fig. 61); their lateral outline simple, without any lobes or incisions.
Comparative notes.Idiotrephes thai differs from all other Idiotrephes species by the human head-like apex of the aedeagus, and relatively narrow but robust first valvifers and valvulae.

N. Nieser N9522 (CNTN).
Etymology.This species is named after the country of its ori gin, Thailand, which is so extremely diverse in different clades of Helotrephidae.
Habitats.The type locality is a small stream in a quite open area with degraded forests.The stream is extremely slowly flowing and shallow where the specimens were found.The limestone bottom forms small connected pools and is thickly covered with algae due to the open, unshaded conditions.Idi otrephes thai sp.n. was found on the bottom of the stream inter mixed with I. asiaticus sp.n.Male: Aedeagus with relatively short distal part, apex recurved and pointed (Fig. 46).Left paramere (Fig. 47) with rectangular basal part and very slender distal part; right paramere (Fig. 48) distally broad, apex truncate.
Comparative notes.Idiotrephes shepardi differs from all other Idiotrephes species by the caudally recurved apex of the aedeagus of males, and by the anterolateral incision of the first right valvula in females.
Etymology.Named in honour of Prof. William D. Shepard (Sacramento), who provided us with numerous interesting Helotrephidae collected in Thailand and Malaysia.
Habitats.The type locality is a rather small stream slowly flowing through a mountainous pine forest in the Nam Nao National Park.Specimens were collected by the second author along the edges of lentic areas of this stream.

Figs
Figs 63-70: Diagrammatic examples of most frequented out lines of ventral midsternal thoracic carinae in Idiotrephes spe cies.Right lateral view (venter up).63 -I.chinai (I.asiaticus differs mostly only by posteriad pointed metasternal carina); 64 -I.polhemusi; 65 -I.yupae; 66 -I.maior; 67 -I.meszarosi; 68 -I.hainanensis; 69 -I.thai; 70 -I.shepardi.ps, ms, and mt -pro-, meso-, and metasternal carinae respectively.DISCUSSIONDistribution, discrimination of species, interspecific similarities, and relationshipsWe do not yet have any information about the occur rence of Idiotrephes in Java.Also, several expeditions by the second author failed to find this species in the Philip pines, although its occurrence in Palawan seems possible.No Idiotrephes species are known to us from Burma, Laos, and Cambodia.Two species are most abundant and widely distributed in southeast Asia, I. asiaticus (on the mainland) and I. chinai (in the Indomalayan archipelago); they are sympatric in the southern part of west Malaysia.Both species have many morphological similarities and variable char acters.After analysing the material of these species, two controversial hypotheses appeared: (1) the material repre sents only one species with series from somewhat dif ferent and variable local populations; (2) the material rep resents two species, each with somewhat different and variable local populations.Detailed study of the mor phology of terminalia (especially apex of aedeagus, and shape of posterior corners of the first valvulae) in rela tively large series of specimens from different areas, morphometrical characters (especially angle 8, and vl/vw ratio), as well as the sympatric occurrence of two distinct morphospecies (without intermediate forms) in peninsular Malaysia, evidently support the second hypothesis.We have not had any possibility to verify this hypothesis from the biological or genetical points of view, but in our opinion I. asiaticus and I. chinai are good species, not merely arbitrarily separated taxa.Other species have smaller areas of distribution than I. asiaticus and I. chinai.Except I. hainanensis, they live mainly sympatrically with I. asiaticus.Their relationships ). Coll.P.P. Chen, Beijing, China; CSS -Coll.W.D. Shepard, California State University, Sacramento, USA; CZVA -Coll.H. Zettel, Vienna, Austria; JTPC -Coll.J.T. Polhemus, Engle wood, Colorado, USA; FSFM -Coll.D. Kovac, Forschungsin stitut Senckenberg, Entomologie I, Frankfurt am Main, Germany; KKUA -Khon Kaen University, Faculty of Agricul ture, Department of Entomology, Khon Kaen, Thailand; NHMW -Naturhistorisches Museum in Wien, Vienna, Austria; NHRS -Naturhistoriska Riksmuseet, Stockholm, Sweden; UBCB -Coll.M. Papáček, University of South Bohemia, České Budějovice, Czech Republic.

Table 2 .
Some morphometrical characters of males of I. asiaticus.Explanation of abbreviations as in Table1.