A review of the Larainae of Australia with description of seven new species and the new genus Australara (Coleoptera, Byrrhoidea, Elmidae)

Abstract The three genera and four species of Larainae (Elmidae) previously described from Australia are reviewed, and one new genus and seven new species are described: Australaraglaisterigen. et sp. nov., Ovolaralawrenceisp. nov., Ovolaramonteithisp. nov., Stetholuscarinatussp. nov., Stetholuslongipennissp. nov., Stetholusmetatibialissp. nov., and Stetholusworonorasp. nov. A lectotype is designated for Hydoralaticeps (Carter & Zeck), and the first new collection records of the species are reported since its description in 1932. The occurrence in Australia of Potamophilinuspapuanus Satô, described from Papua New Guinea, is reported. A key to the species, photographic images of the external morphology and male genitalia, distribution maps, and habitat and behavioral information, when known, are provided for all twelve species of Australian Larainae.


Introduction
The aquatic beetle family Elmidae is traditionally divided into two subfamilies, the Elminae and the Larainae. The Elminae are by far the most diverse of the two, with 123 genera and nearly 1,350 recognized species worldwide, whereas the Larainae have only Geographic abbreviations used in the text include: ACT = Australian Capital Territory; NSW = New South Wales; QLD = Queensland; NQLD, NQ, N. Qld. = north Queensland; VIC = Victoria.

Study material
The authors examined a total of 540 specimens during this project. These were borrowed from Australian institutional collections (AM, ANIC, QM, SAMA) or were collected by the authors and, in the case of one new species, by European colleagues.

Field techniques
Specimens collected by the authors were manually dislodged from surfaces and objects, then captured in aquatic nets, or were swept from streamside and emergent vegetation. The collections were placed in vials containing 95 % ethanol in the field and examined later in the laboratory. Related taxa collected with the laraines are reported in the species treatments as "Associated byrrhoid taxa."

Laboratory procedures
Examination and measurement of specimens were done with a Leica MZ 12.5, fitted with an ocular micrometer, and an AO Spencer Model 25 stereo microscope. A series of species from each of the authors' collection localities was dried and point-mounted after genitalic dissection. Specimens on loan also were often dissected for genitalic examination, and those previously glued to card mounts were remounted as was necessary. After study, the genitalia were placed in vials, each containing a drop of glycerin, and affixed to pins below the specimens. For almost all species with sufficient numbers, some specimens were further dissected to view other structures more accurately such as antennae, mouthparts, elytra, and metathoracic wings. The dissected parts were then slide mounted and examined. Measurements of body length consist of the pronotal length plus the elytral length taken at the midline, and do not include the head or the variable space between the pronotum and elytra; measurements of width are of both elytra at their widest point.

Specimen imaging and distribution mapping
Most of the habitus images were taken using a Visionary Digital BK Plus Lab System fitted with a Canon EOS 7D camera. Some of the images were provided by staff at museums where the specimens are housed, as noted in the figure legends and the Acknowledgments. The genitalia images were taken with a Syncroscopy AutoMontage ® system. Images were prepared and assembled using Adobe Photoshop Elements.
SimpleMappr, a free internet program (Shorthouse 2010), was used to create the species distribution maps (Figs 1-12). Geographical coordinates for specimens collected by the authors were obtained using a hand-held GPS unit. For museum speci- Type species. Australara glaisteri sp. nov. Differential diagnosis. Australara (Fig. 13) is distinguished by the following characters: Body shape elongate; antennae subserrate, thin, very long; eyes moderately protuberant; maxillary palpi long and robust, apices tapered, sensory areas oblique and narrowly oval; labial palpomere 3 apex with white, digitiform, sensory area; pronotum with two faint, anterior transverse impressions laterad of the midline, basal sublateral carinae absent; prosternum moderately short anterior to procoxae, not extending beneath head; prosternal process spinose; mesoventrite with a narrow projection from the anterior margin containing a slit-like mesoventral cavity to receive the prosternal process; apices of hind tibiae exceeding the elytral apex.
Description. Body elongate; setose, setae longer and more dense on venter than on dorsum. Antenna thin, very long, antennomeres 3-11 subserrate; eye moderately protuberant, subcircular at base; maxillary palpus long and robust, palpomere 4 with apex tapered, sensory area oblique, narrowly oval. Pronotum lightly sculptured with a pair of faint anterior transverse impressions and a pair of elongate basal sublateral impressions. Elytron marginate, shallowly punctate and striate, apex acute. Prosternum moderately short anterior to procoxae, not extending anteriorly beneath head; prosternal process long, spinose, carinate. Mesoventrite with a narrow projection from the anterior margin containing a slit-like mesoventral cavity. Abdominal ventrites 1 and 2 Figures 13, 14. Australara glaisteri gen. nov., sp. nov., male 13 habitus A dorsal B ventral (photographs courtesy of the Australian National Insect Collection, CSIRO, Zhenhua Liu) 14 male genitalia A dorsal view B lateral view C ventral view. combined much shorter than ventrites 3-5 combined. Legs long, slender, apex of hind tibia extending beyond elytral apex.
Etymology. From the Latin australis, meaning southern, in reference to the Southern Hemisphere as well as the continent of Australia, plus Lara, the type genus of the subfamily Larainae.
Distribution. Known only from the type locality in north Queensland, Australia (Fig. 1).
Comments. Described from only three specimens, all males, from one locality. The larva is unknown. Differential diagnosis. Australara glaisteri (Figs 13,14) may be separated from other laraine species by the characters given in the generic diagnosis: Hydora laticeps  shares some similarities, but differs by having strong sublateral pronotal carinae, whereas A. glaisteri has none. Unlike A. glaisteri, Stetholus species  have shorter, distinctly clavate antennae, and the prosternum is very short anterior to the procoxae. The male genitalia of A. glaisteri (Fig. 14) are unusual, with the penis curved strongly in a dorsal direction.
Variation. The three specimens varied in size from 3.7-4.0 mm long and 1.4-1.5 mm wide. Because the small series of A. glaisteri is all male, it was not possible to make a comparison with the female of the species. Among the three, the two shallow, elongate, sublateral pronotal impressions vary from faint to distinct. Also, the posterior pronotal angles differ in the amount to which they are produced, the shape of the angle (nearly 90° to acute), and whether the tip is truncate, blunt, or sharp. It is possible that the median emargination on the posterior margin of abdominal ventrite 5 is a male characteristic not present in females.
Etymology. The specific epithet glaisteri, a noun in the genitive case, is given in honor of Alena Glaister of Monash University, VIC, who devised a successful method of rearing Australian larval elmids to adults, thereby enabling their association. She published an extensively illustrated identification guide to the larval Elmidae of Australia with keys and descriptive notes on taxonomy, distribution, and habitat. Few elmid researchers have attempted such work, and none have produced larval keys covering so many taxa.
Distribution. Known only from the type locality in north Queensland, Australia (Fig. 1).
Habitat. At the collection site during low water stage, the Mulgrave River was mostly shallow, with warm, clear water and a fairly swift current over a substrate of sand and gravel. Decomposing wood and log jams, where Australara and other laraines were found, were abundant along the banks of the wide channel. The locality is at ~ 30 m elevation and bordered by a town and sugarcane fields not far from the ocean. Local residents told us that in past years saltwater crocodiles frequented the river until the sugarcane farmers shot them out.
Distribution. The genus Hydora has an interesting geographic distribution, with ten recognized species occurring in New Zealand (7), Australia (1), and Argentina and Chile (2) (Spangler and Brown 1981;Lambert et al. 2014). There are many currently undescribed species in New Zealand and one in Chile (R. Leschen, V. Sýkora, in litt.).
Habitat and behavior. There is no information available pertaining to the habitat and behavior of Hydora in Australia, except for the fact that at least half of the known specimens were collected at lights. In New Zealand, larvae and adult Hydora are common on the bottom substrate, or on vegetation, including bryophytes, at the margins of moderate to fast flowing streams (Lambert et al. 2014). Adults can sometimes be found running around on the emergent parts of boulders and have been observed in mass swarms above the water surface (Lambert et al. 2014).
Comments. In this genus the prosternal process may or may not have a median longitudinal carina, depending on the species. Some New Zealand species do, and some do not (Broun 1914;Lambert et al. 2014). No carinae were mentioned in the descriptions of the prosternal processes of the two species from Austral South America, Hydora annectens Spangler & Brown and H. lenta Spangler & Brown (Spangler and Brown 1981), and upon examining specimens of those species, we found none. The description of H. laticeps from Australia stated that the process is without a carina (Carter & Zeck 1932), but this is debatable. The prosternal process is discussed in the Comments section of the species treatment. The larva was keyed and illustrated at the generic level in Glaister (1999)  Differential diagnosis (n = 8). Hydora laticeps  is the only species of Hydora known to occur in Australia. It can be distinguished from other Australian laraines by a combination of the following characters: Eyes protuberant, hemispherical; maxillary palpi narrow at the apices; pronotum with strong basal, sublateral carinae and without a distinct transverse impression at anterior 1/3; and prosternum moderately long anterior to the coxae but not extending beneath head. Stetholus species (Figs 34-42) have ovoid eyes, not usually prominent; maxillary palpi each with palpomere 4 wide and oblique at the apex; pronotum with a distinct transverse impression; and prosternum very short and narrow anterior to the coxae.
Australara glaisteri (Fig. 13) most obviously differs by its lack of sublateral pronotal carinae and by the mesoventrite having an anterior projection containing a slit-like mesoventral cavity; the eyes are also not quite as protuberant.
Variation. There is some size variation among the known specimens, particularly between males and females. Specimens from the type series, all males (n = 4), measured 4.0-4.3 mm long, 1.4-1.6 mm wide. Carter and Zeck (1932) stated in the type description "Dimensions: 5 × 1.5 mm" but the length probably included the head. Among the specimens examined (including two from the type series), the females (n = 3), 4.5-5.2 mm long, 1.7-1.8 mm wide, are considerably larger than the males (n = 3), 4.0-4.5 mm long, 1.4-1.6 mm wide. In addition, the females (Figs 20B, 22B) have prosternal processes broader than those of the males (Fig. 15C), and noticeably narrower maxillary palpi. The prosternal processes of the two male specimens examined from the type series ( Fig. 15C) are slightly narrower than those of the non-type male. The surface of the prosternal process varies, and may be convex, depressed only between the procoxae, or entirely flat except posterior to coxae, but in all specimens the process is granulate, swollen, and an indistinct carina is usually visible. Non-sexual variation was also observed in the morphology of the elytral punctures (size and depth), pronotum (width, lateral margins, posterior angles, sculpturing); and prosternal process (width, surface features). On the pronotum, two shallow, anterior, transverse impressions are present laterad of the midline. In most specimens the impressions are weak or altogether ob- scure , but they are quite obvious in one of the two non-type specimens from Cann River (Fig. 22A). In addition, the single male non-type specimen from Lyneham ( Fig. 21A, C) has a slightly broader aedeagus than the two specimens examined from the type series ( Fig. 16A, C). This variability in external morphology and male genitalia raises the possibility that more than one species is involved.
Lectotype designation. It appears that none of the four known specimens from the type series of Stetholus laticeps was given a holotype or paratype label at the time of description, and those subsequently added to the specimens were not done so by the authors. In their description, Carter and Zeck (1932) stated that they had "five examples" and that the holotype was "in Coll. Carter," but did not mention designating paratypes. Two specimens were deposited at the Australian Museum 35 years apart: According to the original register of specimens, the first ( Fig. 15) was presented by H. J. Carter in 1936, and bears an old, handwritten determination label saying "Stetholus laticeps Carter & Zeck Id. by H. J. Carter" (Fig. 15A). The specimen was subsequently given a holotype label by an unknown person, i.e., it was not written in the same hand as the determination label by Carter and appears much newer. This specimen is here designated as the lectotype to fix the concept of Hydora laticeps (Carter & Zeck). The second specimen (Fig. 17)  original determination label, and likewise bears a newer paratype label; it is designated a paralectotype.
There are also two specimens housed at Australian National Insect Collection. One of them bears the surprising, original determination label "Stetholus elongatus C & Z Id. by H. J. Carter" and two printed paratype labels, one older and one newer (Fig. 19). Probably the identification predated the description of S. laticeps by Carter and Zeck in 1932, however, Tallong was not among the localities cited in their 1929 description of S. elongatus (Carter and Zeck 1929). The other specimen has an original determination label, "Stetholus laticeps C & Z Id. by H. J. Carter," but has no paratype label (Fig.  18). These two specimens are likewise designated as paralectotypes. We were unable to examine the ANIC specimens because they were on loan to another researcher, but we were provided with habitus images (Figs 18,19) and measurements of body length for this article.
The location of the fifth specimen from the type series is unknown. Lambert et al. (2014) cited the SAMA as a specimen depository for the species, but we have examined their material and found no specimens of H. laticeps, so this report was in error.
Distribution. Hydora laticeps is known from only three localities in Australia: the Shoalhaven River near Tallong, New South Wales, the type locality; Lyneham, Australian Capital Territory; and Cann River, eastern Victoria (Fig. 2).
Comments. Hydora laticeps was originally described in the genus Stetholus by Carter and Zeck (1932), and subsequently reassigned to Hydora by Hinton (1935). Hinton stated that he studied only the description and figures, not actual specimens, and gave no specific reasons for the new combination.
In the diagnosis following their description, Carter and Zeck (1932: 203) noted that the prosternal process of S. laticeps lacks a carina, in contrast to Stetholus elongatus Carter & Zeck (1929) which has a carina. The actual situation is less clear-cut. The surface of the apical 1/2-1/3 of the process is convex to varying degrees and may be somewhat granulate at the midline, resembling an indistinct carina. However, this is a poor diagnostic character because dense setation can make examination difficult.
When Carter and Zeck (1932) described S. laticeps they made no mention that S. elongatus, described by them in 1929, was present in the Upper Shoalhaven River as well. That S. elongatus was collected with H. laticeps at the type locality is evidenced by museum specimens with locality labels identical to those of H. laticeps: "Tallong N.S.W. FH Taylor." This raised the question as to whether the missing specimen of H. laticeps might bear a S. elongatus label, as does one of the ANIC specimens, and thus has been overlooked. Unfortunately, examination of all known S. elongatus specimens with collection labels as above (AM, 3 specimens; ANIC, 3; NMV, 2; SAMA, 4) revealed no misidentifications.
Until now, Hydora laticeps has been known only from its type locality, the Upper Shoalhaven River near Tallong, New South Wales, Australia. In the 90+ years since the type series was collected, deliberate attempts to re-collect it have been unsuccessful. Examination of unidentified museum specimens for this project resulted in the discovery of four additional specimens from two new localities, all of which were collected at light. The four type specimens available are all males, the Lyneham specimens are male and female, and the Cann River specimens are both female. In the absence of males, the latter two specimens are assumed to be H. laticeps due to external morphological similarities. The larva of the species is unknown. As mentioned in the Variation section, is possible that not all of the specimens are conspecific because of mophological variation which is apparent even among those from the type series. However, there is not enough evidence at present to assign any to a species other than H. laticeps. DNA analysis would be helpful in this regard if fresh material could be obtained. A recent attempt to obtain DNA from a specimen in the type series failed due to its age (V. Sýkora, in litt.), and even the youngest of the specimens is at least 54 years old.

Distribution. Ovolara is endemic to Australia, with four species occurring in New South Wales and Queensland (Figs 3-6)
Habitat and behavior. Ovolara adults are most often associated with marginal or emergent stream vegetation and debris packs. Depending on the species, they may occur in areas of slow current (O. australis) or in fast water and rapids (O. leai). When captured or disturbed, Ovolara does not take flight as quickly as many other laraines. Specimens of all species have been collected at lights.
Comment. King (1865) described the type species of the genus in Lutochrus, a misspelling of Lutrochus Erichson, 1847. Brown (1981) subsequently erected the genus Ovolara to include the type species, Lutrochus [sic] australis as well as Hydrethus leai Carter, 1926(Brown 1981. He believed the genus to be most closely related to Hydora. The larva was keyed and illustrated in Glaister (1999) at the generic level.
The external morphology of the species is very similar except for that of O. australis. Comparison of the male genitalia is the best way to distinguish the species.
Material examined ( Variation. The only difference observed among individuals is the degree of pronotal sculpturing, especially the depth of the median longitudinal sulcus. Measured specimens vary in size from 3.3-4.2 mm long and 1.4-1.7 mm wide (n = 30). There is little size difference between males, 3.3-4.1 mm long, 1.4-1.7 mm wide (n = 19), and females, 3.4-4.2 mm long, 1.5-1.7 mm wide (n = 11), with individuals of both at the small and large ends of the size range.
Distribution. Ovolara australis occurs in New South Wales and south Queensland, Australia (Fig. 3).
Habitat, behavior, and life history. The authors found O. australis adults to be numerous in blackwater streams beneath undercut clumps of emergent vegetation in areas of sluggish flow. The species also has been taken at black light by the authors and other collectors. One female specimen, collected in January, was dissected and found to have 20+ eggs in her abdomen, indicating that January is within the reproductive period of the species.
Comments. Ovolara australis, the type species of the genus, was originally described by King (1865) in Lutochrus, a misspelling of Lutrochus Erichson, 1847; it was moved to Ovolara by Brown (1981). The larva of this species has been reared to the adult by Glaister (A. Glaister, in litt.).  Differential diagnosis. Ovolara lawrencei (Figs 25,26) can be distinguished from other species of Ovolara (Figs 23, 24, 28-31) by a combination of the following characters: Antennae clavate, elongate; pronotum mostly smooth, unsculptured, except basal margin triangularly protuberant between the prescutellar foveae; pronotal basal sublateral carinae generally shorter than the length of the scutellar shield; elytra without accessory basal striae between striae 1 and 2; and elytral punctures large and deep from base to apex. The aedeagus (Fig. 26) is unique, with the paramere inner margins linear and clasping the apical 1/3 of the tapered, narrow penis.

Ovolara lawrencei
The other three species of Ovolara have elytral accessory striae of varying lengths, sometimes as short as 1-3 punctures. In addition, Ovolara australis (Fig. 23) has an antenna with a stout, moderately tight, ovoid club; pronotum sculptured, with a distinct longitudinal sulcus and costa; and an aedeagus ( Fig. 24) with the penis abruptly constricted at the apex and the adjacent paramere apices rounded. In O. leai (Fig. 28), the pronotal mediobasal margin is less-prominently raised; the pronotal basal sublateral carinae are as long as or longer than the scutellar shield; the apical elytral punctures are smaller and shallower than those more basal; and the aedeagus (Fig. 29) has a penis that is abruptly constricted at the middle and paramere apices that are rounded, each bearing an inner tooth. Ovolara monteithi (Fig. 30) has the pronotal base flat; the pronotal basal sublateral carinae as long or longer than the scutellar shield; and the aedeagus ( Fig. 31) with the lateral margins of the penis evenly convergent to an acute apex. All species, except for O. australis, are quite similar, and most of the above characters are somewhat variable and overlapping. Fortunately the male genitalia (Fig. 26) are distinctive and diagnostic, and are therefore the best, most reliable, identification tool.
Variation. Very little morphological variation was noted, except for small differences in the length of the pronotal sublateral carinae. Sizes range from 2.9-3.3 mm long and 1.3-1.4 mm wide (n = 19). The females measured are slightly larger than the males, but the female sample size is considerably smaller: females 3.0-3.3 long, 1.3-1.4 mm wide (n = 5); males 2.9-3.1 mm long, 1.3 mm wide (n = 14).
Etymology. The specific epithet lawrencei, a noun in the genitive case, is given in honor of John F. Lawrence, arguably the most influential and prolific coleopterist of our time. An excellent review of his life and career was published by Newton et al. (2000), although somewhat prematurely because Lawrence has by no means retired.
Habitat and behavior. Ovolara lawrencei was collected by the authors in small to large streams at elevations ranging from 18-654 m. All but one of these were sandbottomed with logs and debris, some with boulders, and one had a bedrock substrate. Their waters were warm to cool, clear and colorless to brown-stained, with currents varying from sluggish to fast. At Emerald Creek (Fig. 27), the type locality at an elevation of ~ 415 m, the stream was large with a substrate of sand, gravel and boulders. Ovolara lawrencei specimens were found in areas of slow current among streamside vegetation, grassy margins, and debris packs, and also in faster current on logs and rocks. The beetles "played dead" in the net, remaining immobile for a period of time, and were difficult to see amongst the netted debris. The easiest method to locate them was to hold the net and debris in the water and wait for them to pop up to the surface. They did not fly readily. Specimens have been taken at light, including those collected by Monteith (G. Monteith, in litt.  Differential diagnosis (n = 78). Ovolara leai (Figs 28, 29) can be distinguished from other species of Ovolara (Figs 23-26, 30, 31) by a combination of the following characters: Antennae clavate, elongate; pronotum mostly smooth, unsculptured, with base only weakly protuberant between prescutellar foveae, if at all; pronotal basal sublateral carinae as long as or longer than the scutellar shield; elytron each with a very short, accessory basal stria of 1-3 punctures between striae 1 and 2, rarely obscure; apical elytral punctures smaller and shallower than those more basal; and the aedeagus (Fig. 29) with a penis that is abruptly constricted at the middle, and paramere apices that are rounded, each bearing an inner tooth.
Ovolara australis (Fig. 23) has an antenna with a stout, moderately tight, ovoid club; a sculptured pronotum with a distinct longitudinal sulcus and costa; and an aedeagus (Fig. 24) with the penis abruptly constricted at the apex and the adjacent paramere apices rounded. Ovolara lawrencei (Fig. 25) has a pronotum with the basal margin triangularly protuberant between the prescutellar foveae; pronotal basal sublateral carinae generally shorter than the length of the scutellar shield; no elytral accessory basal striae; elytral punctures large and deep from base to apex; and unique aedeagus ( Fig. 26) with the paramere inner margins linear and clasping the apical 1/3 of the tapered, narrow penis. Ovolara monteithi (Fig. 30) has the pronotal base flat; apical elytral punctures large and deep; and the aedeagus (Fig. 31) with the penis lateral margins evenly convergent to an acute apex. All species, except for O. australis, are fairly similar externally, and the above characters are somewhat variable and overlapping. Fortunately the male genitalia (Fig. 29) are distinctive and diagnostic.
Variation. Very little morphological variation was noted except for differences in the number punctures in the elytral accessory stria (1-3, rarely obscure), which sometimes varies between elytra on the same individual. Small differences in the length of the pronotal sublateral carinae were also observed. Measured specimens vary in size from 3.1-3.5 mm long and 1.4-1.5 mm wide (n = 18). The females are slightly larger than the males: females 3.3-3.5 mm long, 1.4-1.5 mm wide (n = 7); males 3.1-3.4 mm long, 1.4-1.5 mm wide (n = 11).
Habitat. The authors collected this species from only two localities: Freshwater Creek at Freshwater, a large, sand-bottomed stream at an elevation of 5 m; and the Mulgrave River just south of Gordonvale, a wide, sand-bottomed river at 9 m. In both, the water was warm and clear, and the current swift. In the Mulgrave River, O. leai was collected from wood in rapids formed by log jams. Specimens from the QM collected by Monteith were most likely from lights (G. Monteith, in litt.  Differential diagnosis. Ovolara monteithi (Figs 30, 31) can be distinguished from other species of Ovolara (Figs 23-26, 28, 29) by a combination of the following characters: Antennae clavate, elongate; pronotum smooth, unsculptured, pronotal base flat; pronotal basal sublateral carinae as long or longer than the scutellar shield; each elytron with a short accessory basal stria of 1-3 punctures between striae 1 and 2; apical elytral punctures large and deep; and aedeagus ( Fig. 31) with the penis lateral margins evenly convergent to an acute apex.
Ovolara australis (Fig. 23) has an antenna with a stout, moderately tight, ovoid club and a sculptured pronotum with a distinct longitudinal sulcus and costa; and an aedeagus ( Fig. 24) with the penis abruptly constricted at the apex and the adjacent paramere apices rounded. Ovolara lawrencei (Fig. 25) has the pronotal basal margin protuberant between the prescutellar fovea; the pronotal basal sublateral carinae generally shorter than the length of the scutellar shield; no elytral accessory striae; and a unique aedeagus (Fig. 26) with the paramere inner margins linear and clasping the apical 1/3 of the tapered, narrow penis. In O. leai (Fig. 28), the apical elytral punctures are smaller and shallower than those more basal; and the aedeagus (Fig. 29) has a penis that is abruptly constricted at the middle, and paramere apices that are rounded, each bearing an inner tooth. All species, except for O. australis, are fairly similar externally, and the above characters are somewhat variable and overlapping. Fortunately the male genitalia ( Fig. 31) are distinctive and diagnostic.
Variation. Very little morphological variation was noted except for differences in the number of punctures (1)(2)(3) in the elytral accessory striae, which is sometimes variable between elytra on the same individual. Differences were also observed in the length of the pronotal sublateral carinae which can be up to 1/4 the length of the pronotum or shorter. Measured specimens vary in size from 2.9-3.6 mm long and 1.2-1.5 mm wide (n = 11). The sizes of the males and females overlap, but the females are generally larger than the males: females 3.2-3.6 long, 1.3-1.5 mm wide (n = 6); males 2.9-3.4 mm long, 1.2-1.4 mm wide (n = 5).
Etymology. The specific epithet monteithi, a noun in the genitive case, is given in honor of Geoffrey Monteith of the Queensland Museum who has collected > 200,000 insects, including nearly all of the specimens of Elmidae housed there.
Habitat. The specimens collected at the type locality, Millaa Millaa Falls Park on the Atherton Tableland, were taken at mercury vapor light near a large waterfall at 780 m elevation (G. Monteith, in litt.). The other six collection localities included streams and small rivers in rainforest, remnant rainforest, and farmland habitats at elevations from 20-850 m. Most of the QM specimens were collected at mercury vapor lights near streams and rivers (G. Monteith, in litt.).
Distribution. Thirteen species of Potamophilinus occur from eastern Asia to Australia.
In his unpublished checklist of elmid species, Calder (1992) listed an undescribed species of Potamophilinus from north Queensland based on three specimens in ANIC labeled "W. Claudie River / Iron Range, NQ / 13 May 1971 / J.G.Brooks". We examined the specimens and concluded that they are P. papuanus Satô, described from New Guinea, by comparison with paratypes of that species, the original description, and the male genitalia. Lawrence and Britton (1994) first reported the genus from Australia, probably from Calder's determination. As mentioned in the differential diagnosis, two other genera of Larainae besides Potamophilinus occur in nearby Papua New Guinea, Potamophilus and Parapotamophilus. Possibly they too will be found in Australia in the future. Glaister (1999) keyed and illustrated larvae from the Northern Territory which she assumed to be Potamophilinus, but this was not verified by rearing to adult. Differential diagnosis (n = 15). Body (Fig. 32) elongate, sides subparallel; antennae loosely clavate, not reaching to middle of pronotum; maxillary palpi each with tip of palpomere 4 obliquely truncate, elliptical; labial palpi with tip of palpomere 3 truncate, oval; pronotum flat, with a wide, U-shaped, transverse impression at anterior 1/3, without basal sublateral carinae; pronotal anterior angles depressed, posterior angles blunt, each with a large, adjacent oval depression; elytra striate-punctate, apices angulate; pro-and mesofemora broad and anteriorly flattened to slightly concave; prosternal process very long, carinate, broad between procoxae, abruptly narrowed and spinose between mesocoxae, apex acuminate; apices of metatibiae exceeding apices of elytra; abdomen with six visible ventrites, loosely fitted to epipleura; aedeagus (Fig. 33) very long and slender; penis and parameres abruptly angled at base; parameres fused with penis basally and appressed apically. Potamophilinus papuanus (Fig. 32) is easily differentiated from all other Australian laraines by characteristics of the pronotum, elytral apices, prosternal process, and unusual male genitalia (Fig. 33).

Potamophilinus papuanus Satô, 1973
Variation. Measured specimens from Australia vary in size from 4.4-4.9 mm long and 1.7-2.1 mm wide (n = 11). The females are larger than the males, but the sample size is small: females 4.6-4.9 mm long, 1.8-2.1 mm wide (n = 6); males 4.4-4.7 mm long, 1.7-1.9 mm wide (n = 5). In the species description, Satô (1973) reported a much wider size range in Papua New Guinea specimens: 4.2-5.6 mm long, 1.6-2.1 mm wide. In measurements of two specimens from the type series, the male is a full millimeter shorter than the female. The species is sexually dimorphic with males having the elytral apices truncate and angulate, and females having the elytral apices broadly rounded except for each with a deflexed, triangular tooth near the inner margin (visible in posterior view).
Distribution. Potamophilinus papuanus occurs in Papua New Guinea, north Queensland (Fig. 7) and possibly the Northern Territory (Glaister 1992(Glaister , 1999, Australia. Habitat and life history. Our few records of P. papuanus are from large, sandbottomed creeks with warm, clear water where specimens were collected from logs and branches in fast current. In the NT, Potamophilinus larvae occur among matted roots at margins of sandy streams (A. Glaister, in litt.). Three adult females, all collected in January, were dissected in the lab and had eggs in their abdomens: two had four eggs each and one had > 20 eggs. Therefore, January is within the reproductive period of the species. One of the specimens examined from New Guinea was collected in a light trap, as was the QM specimen although not labeled as such (G. Monteith, in litt. Comments. Potamophilinus papuanus was described from Papua New Guinea, and its occurrence in Australia is not listed in the world elmid catalog by Jäch et al. (2016). In order to confirm the species identification we examined two paratypes of P. papuanus from New Guinea and compared Satô's illustration of the male genitalia (Satô 1973) with the genitalia of four Australian specimens from north Queensland.
Distribution. Stetholus is endemic to Australia, with species occurring in Queensland, the Australian Capital Territory, New South Wales and Victoria (Figs 8-12). There was a record in the Atlas of Living Australia (ALA) https://www.ala.org.au/ database of a specimen from Tasmania, but the specimen was misidentified therefore the record was erroneous (S. Grove, in litt.). It has since been deleted.
Habitat and behavior. Adults are usually found in fast or turbulent water in rocky chutes, below waterfalls and spillways, on log jams and boulders in rapids, and among root masses in the current, often in large aggregations. They fly readily when disturbed. Specimens also have been collected with light traps and flight intercept traps (A. Glaister, in litt.; G. Monteith, in litt.).
Comments. Three of the five known species exhibit secondary sexual dimorphism with the females having the posterior 1/4 of the elytron slightly explanate lateral to stria 11. This is most pronounced in S. longipennis sp. nov., but is less so and somewhat variable in S. elongatus and S. woronora sp. nov. The larva of Stetholus was keyed and illustrated by Glaister (1999 (Figs 34, 35) is characterized by the following: shorter (3.7 mm) than other Stetholus species (3.9 mm or longer) (Figs 36-42); pronotum with a pair of distinct, long, basal sublateral carinae; elytron with a short, faint, accessory basal stria with a few punctures between striae 1 and 2; mesotibiae with posterior surfaces glabrous and shiny, metatibiae entirely setose; male genitalia unique (Fig. 35) (those of S. metatibialis are unknown). The species is separated from all other Stetholus except S. metatibialis (Fig. 40), which it most closely resembles, by the long, basal sublateral pronotal carinae. Stetholus carinatus differs from S. metatibialis as follows: length shorter (3.7 mm vs. 3.9 mm); metatibiae entirely setose; elytron with accessory stria obscure.
Etymology. The specific epithet carinatus, an adjective in the nominative singular derived from the Latin meaning keeled, refers to the presence of a pair of basal, sublateral carinae on the pronotum. Distribution. North Queensland, Australia. Known only from the type locality on the north slope of Mt. Elliot (Fig. 8).
Habitat. Geoff Monteith, one of the collectors, described the area thus: "Mt. Elliot is a high, isolated, rainforest-capped mountain with a strikingly unique and endemic fauna" (G. Monteith, in litt.). The specimen was collected using a flight intercept trap at 1000 m elevation. Carter & Zeck, 1929 Figs 9, 36, 37 Type locality. Allyn River at Gresford; 32.350°S, 151.750°E; New South Wales, Australia (holotype deposited in the Australian Museum, Sydney).
Variation. The examined females exhibit minor secondary sexual dimorphism with the lateral margin of the elytra slightly explanate at the posterior 1/4 laterad to stria 11; in males, stria 11 is just inside the lateral margin, which is not explanate. The metatibia of both sexes has a posterior, linear bare patch which varies in length but is restricted to the basal 1/2, and nearly always the basal 1/3. This character is occasionally obscure, and is probably the result of abrasion of the setae. Otherwise, except for minor differences in the depth and extent of the pronotal impressions, the specimens examined are quite uniform. Measured specimens vary in size from 4.7-5.3 mm long and 1.8-2.1 mm wide (n = 12). The males and the females are of similar size: males 5.0-5.1 mm long, 1.8-2.1 mm wide (n = 7); females 4.7-5.3 mm long, 1.8-2.1 mm wide (n = 5). Carter & Zeck (1929) reported a body length of 5.0-6.0 mm in their species description which likely included the length of the head.
Habitat and behavior. The habitat and behavior of this species is as described for the genus. Populations can be enormous in suitable habitats. Specimens also have been collected in light traps (A. Glaister, in litt.).
Comments. As noted in the Hydora laticeps Comments, there are specimens of S. elongatus in the AM, NMV and SAMA which bear locality labels identical to those of H. laticeps. Carter & Zeck (1929, 1932 made no mention of the S. elongatus specimens from Tallong, or that the two species co-occur. The larva of this species has been reared to the adult by Glaister (A. Glaister, in litt.). characters: Length usually shorter than or equal to 4.6 mm; antennae slender, almost moniliform; pronotum smooth or lightly sculptured, sublateral carinae absent; metatibiae entirely setose; male genitalia with penis very slender and much longer than parameres. Conversely, S. metatibialis (Fig. 40) and S. carinatus (Fig. 34) both have long, distinct sublateral pronotal carinae; S. woronora (Fig. 41) has very short carinae; and all three have distinctly clavate antennae. Stetholus elongatus (Fig. 36) also lacks pronotal carinae, but is usually longer than 4.6 mm and the antennae are clavate. The male genitalia of S. longipennis (Fig. 39) are strikingly different from those of other Stetholus (Figs 35, 37, 42) excluding S. metatibialis for which males are currently unknown.
Variation. The females exhibit minor secondary sexual dimorphism with the lateral elytral margin slightly explanate at the posterior 1/4 laterad of stria 11; in males, stria 11 is just inside the lateral margin, which is not explanate. Measured specimens vary from 4.1-4.6 long and 1.6-1.8 wide (n = 21). The females are slightly larger than the males: females 4.3-4.6 mm long, 1.8 mm wide (n = 8); males 4.1-4.5 mm long, 1.6-1.8 mm wide (n = 13). The width of the prosternal process varies a bit between individuals. Otherwise, except for minor differences in the depth and extent of pronotal impressions, the specimens are quite uniform.
Etymology. The specific epithet longipennis, an adjective in the nominative singular derived from the Latin longi (long) plus pennis (penis), refers to the male genitalia in which the length of the penis greatly exceeds the length of the parameres (Fig. 39).
Habitat and behavior. Stetholus longipennis was collected by the authors from medium to large sand-bottomed streams with logs and debris, some with boulders, and a small river at elevations ranging from 5-417 m (Fig. 27). All had clear water which varied from warm to cool. The beetles were collected from logs and rocks in fast current or rapids, and from a spillway. The adults fly readily from the net, and also have been taken at lights. At the type locality, Hunters Creek, the stream was well-shaded, with many logs and much debris, and many S. longipennis were concentrated on a concrete spillway below a bridge. Differential diagnosis. The single female specimen of S. metatibialis (Fig. 40) is characterized by an elongate-oval body shape; labrum "moustache" composed of two discrete, lateral tufts of very long, dark, curved setae (setal origin unclear, possibly mandibular) (Fig. 40C); long pronotal basal sublateral carinae; and posterior surfaces of both the meso-and metatibiae glabrous and shiny. While other species of Stetholus may have similar labral tufts, none are as long and distinctive. The metatibia of S. Figure 40. Stetholus metatibialis sp. nov., holotype female, 3.9 mm long A dorsal habitus B ventral habitus C head, frontal view D head, ventral view. elongatus (Fig. 36) has a narrow, elongate, posterior bare area of variable length, usually at the basal 1/3, as opposed to that of S. metatibialis in which the posterior surface is entirely bare; the metatibiae of the others are entirely setose. Stetholus elongatus and S. longipennis (Fig. 38) lack pronotal sublateral carinae. Stetholus metatibialis (Fig. 40) bears a superficial resemblance to Ovolara species (28)(29)(30)(31) because of its elongate-oval body and strongly punctate elytra, however it is easily separated by the very short prosternum anterior to the procoxae (vs. prosternum long, extended anteriorly) and the presence of a transverse pronotal impression (vs. no impression).
Etymology. The specific epithet metatibialis is an adjective in the nominative singular derived from the Greek meta meaning after or posterior, and the Latin tibia, the lower portion of a leg. Metatibialis points to the diagnostic character present on the hind tibia, specifically, the glabrous posterior surface (Figs 40D).
Distribution. North Queensland, Australia. Known only from the type locality in the Bellenden Ker Range in Wooroonooran National Park, west of Bellenden Ker and northwest of Babinda (Fig. 11).
Habitat. The single specimen was taken at UV light trap at an elevation of 1054 m on the east slope of Mt. Bellenden Ker. According to the project leader "the whole place is solid rainforest and there are many endemics at higher elevations" (G. Monteith, in litt.).  (Figs 34-40) by a combination of the following characters: Body large, > 5.0 mm long; antennae clavate; pronotum with very short, basal sublateral carinae; male genitalia stout and heavily sclerotized. Stetholus elongatus (Fig. 36) most closely resembles S. woronora but lacks pronotal carinae; the male genitalia are somewhat similar but the penis of S. elongatus (Fig. 37) is narrow and tapered at the apex whereas that of S. woronora (Fig. 42) is wide and bulbous. The other three species of Stetholus are much shorter (4.5 mm or less) and do not have similarly stout, heavily sclerotized genitalia (those of S. metatibialis are unknown). Furthermore, S. longipennis (Fig. 38) lacks sublateral pronotal carinae; S. metatibialis (Fig. 40) and S. carinatus (Fig.  34) both have much longer, more prominent carinae.
Variation. Females exhibit minor secondary sexual dimorphism with the lateral margin of the elytra very slightly explanate at the posterior 1/4 laterad to stria 11; in males, stria 11 is just inside the lateral margin, which is not explanate. The specimens vary from 5.2-5.6 mm long and 1.9-2.2 mm wide (n = 9). Males are slightly larger than the females, but the sample size is small, particularly for females: males 5.3-5.6 mm long, 2.0-2.2 mm wide (n = 6); females 5.2-5.5 mm long, 1.9-2.1 mm wide (n = 3). Except for small differences in the depth and extent of the pronotal impressions, the specimens are otherwise quite uniform.
Etymology. The specific epithet woronora, a noun in the genitive case, refers to the type locality of the species, the Woronora River (Fig. 43). Woronora is an Aboriginal place name meaning black rocks in the Dharug (or Darug) language.
Distribution. New South Wales, Australia. Known only from the type locality south of Sydney (Fig. 12).
Habitat. Although the Woronora River normally has pools interspersed with riffles at the type locality, collector Sýkora (in litt.) reported that due to a severe drought "the river there is pretty much just a small stream and we were surprised there was still some water, given the drought at that time." The specimens were obtained by "water collecting in a small rapids of a small stream in rocky pool" (Sýkora, in litt.) at an elevation of 10 m (Fig. 43).

Distribution, biogeography, and biodiversity
The family Elmidae has both high species richness and endemicity in Australia, but most of that is found in the subfamily Elminae rather than in the Larainae. The vast majority of the described species of both subfamilies are known from along the eastern coast of the continent from Queensland to Victoria. A few elmine species occur in other states, but laraines are known only from Queensland, New South Wales, the Australian Capital Territory, and Victoria. Although island state Tasmania shares five elmine species with the main continent, laraines are apparently absent. This could be an oversight because Tasmania has many streams and rivers, some most likely with suitable habitat. The Australian Wet Tropics bioregion, characterized by high seasonal rainfall, extends along the northeast coast of Queensland from Cooktown to near Townsville, and is topographically varied with mountain ranges containing deep gorges and fastflowing rivers which quickly descend to the coastal plain. Although it encompasses only 0.01 % of Australia, the Wet Tropics sustains a large proportion of the continent's terrestrial plant and vertebrate species, 25 % of which are regional endemics (McKie et al. 2005). The region was placed on the World Heritage list in 1988 in recognition of the high biodiversity and endemism of its rainforest flora and fauna https://www. environment.gov.au/heritage/places/world/wet-tropics.
Intensive surveys of the insects and other invertebrates of the Wet Tropics conducted in the 1980s focused on species diversity, altitudinal zonation, faunal turnover, and biogeography (Yeates and Monteith, 2008). Numerous studies involving aquatic insects were reviewed by Connolly et al. (2008), who concluded that the biodiversity of Wet Tropics streams is high compared to the rest of the continent. The elmids are no exception to this pattern of high biodiversity. Of the 12 species of Larainae known from Australia, eight are found only in north Queensland, including six of the seven newly described species. Five species of laraines, a surprising number, were identified from two rivers and their tributaries, the Daintree and the Mulgrave. It has been determined that the aquatic invertebrate fauna of the Australian Wet Tropics is chiefly of Gondwanan origin, but it also contains some Asian-derived elements (Connolly et al. 2008, McKie et al. 2005. The island of New Guinea and Australia are part of the same continental land mass which separated from Gondwana ~ 96 mya. They formed a single, continuous landmass during the Pleistocene ice age ~ 18,000 years ago until rising sea levels separated them ~ 10,000 years ago. Today, only ~ 150 km separate the tip of the Cape York Peninsula in far north Queensland from Papua New Guinea. Therefore, it is not surprising to find shared fauna between the two, including unusual mammal groups (monotremes and marsupials) and several insect taxa (Yeates andMonteith 2008, Surbakti et al. 2021). Nonetheless, phylogenetic studies of Wet Tropics invertebrates suggest that species from New Guinea and far northern Australia have had little influence (Yeates and Monteith 2008). Instead, their closest relatives are found in coastal rainforests further south in Queensland and New South Wales. So far only one species of laraine shared with New Guinea has been found, Potamophilus papuanus. This species has not only been collected from the Wet Tropics, but also from the Iron Ranges further north in the Cape York Peninsula, an area that shows a much greater faunal overlap with New Guinea (Yeates and Monteith 2008). Besides Potamophilinus, the elmine genera Austrolimnius Carter & Zeck, Coxelmis Carter & Zeck, Graphelmis Delève, and Simsonia Carter & Zeck occur both in Australia and New Guinea. Other laraine genera that occur in New Guinea are Parapotamophilus Brown and Potamophilus Germar, with one and two species, respectively. It would be interesting to discover if any of these taxa are shared as well.
Exploring Australian elmid biodiversity: past research and future potential Taxonomic research on Australian elmids was dominated by H. J. Carter andE. H. Zeck from 1926-1948, who described many new genera and species, including three of the four laraine species. H. E. Hinton named many more species in his monograph on Austrolimnius, an elmine, in 1965. Until now, there has been a 50+ year hiatus since any new Australian elmid taxa have been described. In the interim, ground-breaking descriptive work on the larval fauna was undertaken by Alena Glaister who developed techniques for rearing larvae to adults, thus establishing associations and enabling larval identification (Glaister 1985(Glaister , 1992(Glaister , 1999. Australia has experienced very little focused elmid collecting, both historically and currently, and its elmid diversity is not very well known. The early elmid researchers (e.g., H. J. Carter, E. H. Zeck, H. E. Hinton) worked predominately with museum specimens or relied on local naturalists to send them material. In the 1980s, through the efforts of Geoff Monteith and others who extensively surveyed the Wet Tropics insect and invertebrate fauna, many elmids were captured primarily with light traps or flight intercept traps (Yeates and Monteith 2008). Since then, only a few collectors have added elmid specimens to museum collections. Aquatic invertebrates, particularly the Ephemeroptera, Trichoptera, and Chironomidae (Diptera), have been the focus of numerous surveys as well as ecological studies in the past (Connolly et al. 2008, McKie et al. 2005), but elmids have gotten at most passing mention in the literature despite their abundance in suitable habitats. An exception is a paper on the role of a few species in wood decomposition (McKie and Cranston 1998).
The results of our limited fieldwork in Australia speak volumes to the opportunity for future survey work and taxonomic research, as our experience with laraines in the Wet Tropics of north Queensland illustrates: During a two day period, at seven stream/ river sites on major roads, we collected an undescribed genus, three undescribed species, and a species not yet reported from Australia. Three more new species from that region were found in loan material from the Queensland Museum. Likewise, our elmine collections from north Queensland have proven mostly impossible to identify, and undoubtedly contain many undescribed species because the old taxonomic literature contains relatively few species from north Queensland. Even the more thoroughly explored states of New South Wales and Victoria still hold surprises: Hydora laticeps, previously known only from the type locality for nearly 90 years, was identified from museum specimens collected near Canberra and in coastal Victoria. And most unexpected of all, Stetholus woronora sp. nov. was found just two years ago in the suburbs of Sydney.