﻿Miradessus gen. nov. from South America described for two species previously in Amarodytes Régimbart, 1900 and two new species (Arthropoda, Insecta, Coleoptera, Adephaga, Dytiscidae, Hydroporinae, Bidessini)

﻿Abstract Miradessusgen. nov. is described for two previously described species, Amarodytespulchellus Guignot, 1955 from Colombia, with new records from Venezuela, and A.plaumanni Gschwendtner, 1935, from Brazil, and two previously unknown species, Miradessusbenisp. nov., from Bolivia and Peru, and Miradessusrikaesp. nov. from Ecuador. The genus is characterized by 1) occipital line absent; 2) basal pronotal striae present; 3) basal elytral stria absent; 4) sutural elytral stria absent; 5) transverse carina on elytral epipleuron at humeral angle absent; 6) distinct marginal bead on anterior clypeal margin absent; and 7) male median lobe deeply multilobed with a dorsal portion separate from a unilobed or bilobed ventral portion.


Introduction
The tribe Bidessini Sharp, 1880 includes an unusually large proportion of genera and species of Dytiscidae (Miller and Bergsten 2016). They occur in a great many habitats throughout the world (Miller and Bergsten 2016). New genera have been regularly discovered in recent years through field expeditions in new regions or habitats (e.g. hygropetric or subterranean) and reexamination of historically recognized genera (Miller and Spangler 2008;Miller and García 2011;Miller 2012Miller , 2016aMiller and Short 2015;Miller and Wheeler 2015;Balke et al. 2017).
During a revisionary investigation of the genus Amarodytes Régimbart, 1900 by the authors it became clear that there are several groups of Bidessini species historically involved in the genus that are seemingly more closely related to other groups in Bidessini than to each other. The type species, A. percosioides Régimbart, 1900, is part of a group that includes species with single-segmented lateral lobes that are related to Hydrodessus J. Balfour-Browne, 1953 andPeschetius Guignot, 1942, which also have single-segmented lateral lobes (Miller et al. 2006;Miller and Bergsten 2014, 2016Miller 2016b). However, other species assigned to Amarodytes were found to have two-segmented lateral lobes, and, therefore, are misplaced in the genus (Benetti and Régil Cueto 2004). Two of these species were described as Amarodytes pulchellus Guignot, 1955 andAmarodytes plaumanni Gschwendtner, 1935. Other specimens recently examined from Bolivia and Peru are similar to A. pulchellus, but represent a different, undescribed species described here. Finally, two specimens from Ecuador were also found to represent an unknown species. These species together possess a unique set of character states and cannot be placed into any existing Bidessini genus, nor do they belong in Amarodytes. For this reason, a new genus is here erected to include them. The systematics of Amarodytes will require additional attention to address the A. percosioides-, A. duponti-, and A. segrix-groups which seem unlikely to be appropriately placed in the same genus (Benetti and Régil Cueto 2004).

Materials and methods
Methods for dissections and other treatment of specimens largely follow recommendations by Miller and Bergsten (2016).

Materials
Specimens from nearly every genus of Bidessini were examined, including multiple species from many of them. Specimens of relevant species treated herein were examined primarily from the following collections:

Measurements
Measurements were taken with an ocular scale on a Zeiss Discovery V8 dissecting microscope at 50× magnification. Attempts were made to measure the most variable specimens in size and shape to determine the extent of that variation. Measurements include: 1) total length (TL), 2) greatest width across elytra (GW), 3) greatest pronotal width (PW), 4) greatest width of the head (HW), 5) distance between the eyes (EW), 6) greatest length of metatrochanter (RL), and 7) greatest length of metafemur (FL). The ratios TL/GW, HW/EW, and FL/RL were calculated to provide an indication of relative size and shape of certain structures.

Miradessus
Etymology. This genus is named Miradessus from the Latin miror, meaning to admire, for the impressive color pattern of these beetles, and dessus, a common root for genera in the tribe Bidessini (gender masculine).
Discussion. The species in this new genus are characterized by lateral lobes that are distinctly two-segmented like the majority of Bidessini taxa (Biström 1988;Miller et al. 2006;Miller and Bergsten 2014;2016;Miller 2016b;). Members of typical Amarodytes (including the type species, Amarodytes percosioides Régimbart, 1900) have single-segmented lateral lobes and belong within a clade sister to a clade characterized by two-or three-segmented lateral lobes (Benetti & Miller unpublished). Within the bisegmented lateral-lobe clade, these specimens do not fit well into any other genera (see Diagnosis above). They share some character combinations with Novadessus, Bidessodes, Neobidessodes, the Amarodytes duponti group, and Amarodytes segrix. In some ways they are most superficially similar to members of Bidessodes Régimbart, but specimens in that genus have series of very fine denticles along the posterior margins of the abdominal ventrites (Miller 2017), which are lacking in Miradessus, and also have distinctly different male genitalia (Miller 2017). Miradessus are similar to Neobidessodes, but that genus has simple male median lobes unlike the multilobed condition in Miradessus (Figs 9,11,13,15). Otherwise, they are not similar to other genera in the tribe and are unique because of the prominently apically multilobed male median lobe (Figs 9,11,13,15) which is not found in other genera of Bidessini. Diagnosis. This species and M. pulchellus are extremely similar externally, with similar overall shape, color pattern, and other features (Figs 1, 3). The external differences between them are subtle, including the shape of the prosternal process, which is more prominently laterally carinate and deeply sulcate in M. pulchellus than in M. beni. Also, the ventral surface is darker in most specimens of M. pulchellus than in M. beni. The main differences between these species are in the male genitalia, which are distinctive and characteristic. Both have the median lobe trilobed (with two side portions and a middle portion), but in M. pulchellus the middle portion is nearly as long as the side portions and the apex has a distinct, fine pencil of setae on each side that are divergent (Fig. 13). In M. beni the middle portion is considerably shorter than the side portions and has a series of setae along its apex (Fig. 9). In lateral aspect, the lateral lobe of M. pulchellus has the apical segment nearly as long as the basal segment and it is curved ventrad (Fig. 14). In M. beni the lateral lobe has the apical segment only about 1/3 the length of the basal segment and it is curved dorsad (Fig. 10).
Coloration (Fig. 1). Head yellow-orange. Pronotum yellow-orange with a narrow, rounded lobe of black broadly along each side of posterior margin. Elytron maculate, yellow-orange and black, margins of maculae strongly demarcated; with large, transverse yellow-orange regions anteriorly, medially, and apically, not extending medially to suture, with narrow band of black along entire length of suture, margins of maculae irregular and variously lobed ( Fig. 1). Ventral surfaces mostly orange; legs, epipleuron, and lateral areas of prothorax and head lighter orange-yellow, some sutural margins darker, infuscate, mesothoracic ventrites and prosternal process strongly infuscate to nearly black.
Sexual dimorphism. Males have the pro-and mesotarsomeres I-III slightly but distinctly broader than in females. Abdominal ventrite VI distinctly concave in lateral aspect in females, but medially more expanded and apically somewhat depressed in males. Variation. There is some minor variation in shape and extent of coloration of the dorsal and ventral surfaces but otherwise specimens are similar.
Etymology. This species is named beni after the name Río Beni, the river at the type locality of the species. The name is a noun in apposition.
Distribution. Miradessus beni is known from the type locality in lowland Departmento de La Paz, Bolivia and from two sites in lowland Peru (Fig. 30).
Habitat. The type locality is a heavily forested area of the Andean foothills next to a large river. However, nothing is known of the specific collection habitat of this species.
Material examined. Type material. Holotype   Diagnosis. This species differs considerably from the other known species in the genus. The anterior area of the dorsal surface of the head is testaceous in this species (Fig. 2), but pale yellow in the other species (Figs 1, 3, 4). The ventral portion of the male median lobe in M. plaumanni is broad and unilobate (Fig. 11) instead of strongly bilobate as in the other species (Figs 9, 13, 15). Other differences from other species in the group include: 1) lateral pronotal margins nearly straight posteriorly (Fig. 2) instead of broadly curved (Figs 1, 3,  4), 2) the pronotum and elytron different in color pattern (Fig. 2) from the other, more uniformly-patterned species (Figs 1, 3, 4), and 3) the lateral portions of the metaventrite and metacoxa more coarsely and densely punctate (Fig. 6) than in other species (Figs 5, 7, 8). The general shape and dorsal coloration of specimens are rather different as well (Figs 1-4).
Coloration (Fig. 2). Head brown with a narrow orange band along posterior margin. Pronotum yellow-orange with broad dark band along posterior margin and narrow band along lateral margins. Elytron maculate, yellow-orange and black, margins of maculae strongly demarcated; with transverse yellow-orange regions anteriorly, medially and apically, not extending to suture, with broad band of black along entire length of suture, margins of basal maculae posteriorly bilobed. Ventral surfaces mostly dark orange-brown; legs, epipleuron, and ventral areas of prothorax and head lighter orange-yellow, some sutural margins darker, infuscate, mesothoracic ventrites and prosternal process strongly infuscate.
Sculpture and structure. Head smooth, nearly impunctate, with small micropunctures sparsely distributed; eyes large (HW/EW = 1.7); antennae slender, unmodified. Pronotum with lateral margins moderately curved anteriorly, almost straight posteriorly; with narrow bead along entire margin; surface moderately punctate, punctures more concentrate along posterior margin; lateral pronotal plica strongly impressed, almost straight, extending more than 1/3 distance across pronotum. Elytron with lateral margin evenly and broadly rounded; surface finely and evenly punctate, with a slightly marked line of punctures with short setae extending medially from base to apex. Prosternum medially moderately broad, medially not protruberant, mediolateral surface somewhat granular; prosternal process moderately broad medially with slight tubercle, apical blade large, laterally with low rounded ridges along entire length, medially longitudinally shallowly sulcate, lateral margins almost straight to narrowly rounded apex (Fig. 6). Metaventer and metaventral wings smooth and shiny, covered with coarse, dense, and evenly impressed punctures. Metacoxa with medial portion moderately broad, metacoxal lines distinct, evenly divergent anteriorly to posterior margin of metaventer; lateral portion large, evenly covered with dense, coarse punctures; metatrochanter about 1/3 length of metafemur (Fig. 6). Abdominal ventrites finely punctured with fine setae.
Sexual dimorphism and variation. Males have the pro-and mesotarsomeres I-III slightly but distinctly broader than in females.
Distribution. This species is only known from the type locality, Brazil, Santa Catarina state, Nova Teutônia (Fig. 30).
Sexual dimorphism. Males have the pro-and mesotarsomeres I-III slightly but distinctly broader than in females. Abdominal ventrite VI strongly concave in lateral aspect in females, but medially somewhat swollen and apically with a broadly rounded depression in males.
Variation. There is some minor variation in extent of coloration of the dorsal surface, but otherwise specimens are similar.
Habitat. Specimens have been collected mainly from exposed and sunny areas in lotic margins (small rivers and streams) and nearby pools. They are often numerous in these habitats.
Material examined. Type specimens. Holotype male (Figs 24-26 Other material examined. 134 total examined, all from Venezuela (SEMC), with the following data (SEMC accession numbers in Table 1)  Diagnosis. This species is shorter and more robust (Fig. 4) than either M. pulchellus or M. beni (Figs 1, 3) although the dorsal color pattern is similar to them (Fig. 4). The male genitalia are diagnostic. The median lobe in M. rikae is trilobed like other Miradessus, but the median portion is uniquely short, broad, and apically broadly subtruncate with the ventral portions elongate, slender and apically narrowly rounded (Fig. 15).
Coloration (Fig. 4). Head yellow-orange. Pronotum yellow-orange with a narrow, rounded lobe of black broadly along each side of posterior margin. Elytron maculate, yellow-orange and black, margins of maculae strongly demarcated; with large, transverse yellow-orange regions anteriorly, medially and apically, not extending medially to suture, with narrow band of black along entire length of suture, margins of maculae irregular and variously lobed. Ventral surfaces mostly orange; legs, epipleuron, and lateral areas of prothorax and head lighter orange-yellow.
Male genitalia. Median lobe in ventral aspect conspicuously trilobed, with medial portion short and broad, apically expanded and subtruncate, apicolateral angles with short setae, ventral portions elongate, slender, apically narrowly rounded (Fig. 15); lateral lobe in lateral aspect robust, basal segment somewhat broad and robust, apical segment broad basally, with deep emargination along dorsal margin, apex rounded with series of setae (Fig. 16).
Sexual dimorphism. Only males are known. Variation. The two specimens exhibit slight variation in the shape and extent of maculation on the dorsal surface, but they are otherwise similar.
Etymology. This species is named rikae after Ms Rikelle Timpe, close friend of the first author.
Distribution. Miradessus rikae is known from two sites in Ecuador (Fig. 30).
Habitat. The two known specimens were collected at blacklights, so nothing is known of the specific habitat. The two collection localities are in forested regions of lowland Ecuador.