Megadytes (Bifurcitus) lherminieri (Guérin-Méneville, 1829)

Hendrich, Lars, Manuel, Michael & Balke, Michael, 2019, The return of the Duke - locality data for Megadytes ducalis Sharp, 1882, the world's largest diving beetle, with notes on related species (Coleoptera: Dytiscidae), Zootaxa 4586 (3), pp. 517-535 : 523-525

Megadytes (Bifurcitus) lherminieri (Guérin-Méneville, 1829)

Dytiscus lherminieri Guérin-Méneville, 1829 : pl. 8.

Megadytes giganteus (Laporte, 1835) ; Sharp 1882: 713 (synonymy); Zimmermann 1920: 256; Blackwelder 1944: 80.

Megadytes (Bifurcitus) giganteus (Laporte, 1835) ; Brinck 1945: 8; Trémouilles & Bachmann, 1980: 118; Trémouilles 1989b: 160; Nilsson 2001: 94.

Trogus olivieri Crotch, 1872: 205 , by indication to Dytiscus costalis Fabricius sensu Olivier 1795: 9 ; Wilke 1920: 246 (synonymy).

Megadytes (Bifurcitus) lherminieri (Guérin-Méneville, 1829) ; Nilsson & Fery 2006: 55; Miller & Bergsten 2016: 107; Nilsson & Hájek 2019: 81.

Type localities of Dytiscus lherminieri : Guadeloupe (by indication) ; of Cybister giganteus : Brazil; of Trogus olivieri: French Guyana (Cayenne), Surinam .

Type material. Location of the holotype of D. lherminieri and syntypes of C. giganteus and T. olivieri unknown.

Material examined. Mexico: 1 female, " Mexiko ", " Megadytes giganteus det. Zimmermann " ( ZSM) ; 1 female, "Mexique Salina Cruz " [Oaxaca Provinz ], " Samml. A. Zimmermann " ( ZSM) ; 1 female, " Mex. Behrens ", " R. Mouchamps 1956 Megadytes giganteus Cast. " ; 1 male, " Mexiko – Jalisco Puerto Vallarta 0 3.02.20009 K. Renner ", "Yelapa Wasserfall-Tümpel" ( CLH) ; 1 female, " Mexico Yukatan / Tulum 1.3.- 15.3.2000 leg. O. Blochwitz " ( CLH) ; 1 female: " Mexico Sinaloa 8 mi S. Mazatlan, VII-27-73 " ( CLH) ; Barbados: 1 male, " Barbados: W:I., St. Philipp, pool on Stewarts Hill , 19.xii.1964 " ( BMNH) ; Cayman Islands: 49 exs., " 17.iv- 26.viii.1938. Oxf. Un. CAYMAN IS. Biol. Exped. Coll. By C.B. Lewis, G.H. Thompson", " 28 vii.1938. Grand Cayman, East end of interior Wintersland Cistern."; "Pres. Hope Dept. Oxford B.M. 1967-147", " Megadytes gigantea Laporte det PJSpangler" ( BMNH) ; French Guyana : 1 male, " French Guyana, Awala-Yalimapo, Marais de Panato , pond, N5°44'01" W53°55'48", VII 2003, Manuel & Alié leg. (hand net, by night)" (CMM), 1 female, " French Guyana, Awala-Yalimapo, Marais de Panato , Station de lagunage, N5°44'31.4" W53°55'48.8", 31 VII 2004, Manuel & Timarcha leg. (hand net)" ( CMM) ; 1 male, 1 female, " French Guyana, Awala-Yalimapo, marais de Panato , Station de lagunage, N5°44'32" W53°55'55", 5 VIII 2004, Manuel & Timarcha leg. (trap)" ( CMM) ; Guadeloupe: 1 female, " Guadeloupe, Basse-Terre, Sainte-Rose , Etang du Vieux Fort , N16°21'02.4" W61°45'17.7", 15 V 2012, Manuel leg. (hand net)" ( CMM) , 3 males, " Guadeloupe, Grande-Terre, Le Moule , Etang Fromager , N16°19'18" W61°24'04", 18 V 2012, Manuel leg. (hand net)" ( CMM) ; 4 males, 4 females, Guadeloupe, Grande-Terre, Sainte Anne , in dense belt of Eleocharis surrounding a pond, N16°14'19" W61°21'03.6", 18 VIII 2013, Manuel, Chaillé & Sabroux leg. (traps) ; 3 males, 3 females, " Guadeloupe, Basse-Terre, Sainte Rose , Etang du Vieux Fort , N16°21' 02-04" W61°45' 17-20", 21 VIII 2013, Manuel, Chaillé &

Sabroux leg. (traps)" ( CMM); 1 male, 6 females, Guadeloupe, Grande-Terre, Anse Bertrand, savane Desrosière, pond, N16°30'09" W61°28'25", 27 VIII 2013, Manuel, Chaillé & Sabroux leg. (trap); Puerto Rico: 1 female: "S. Juan 1.6.34 " ( CLH); Panama: 1 male, " Panama, Chiriqui Prov., David , 5.8.1991 , leg. S. Lehmann " ( CLH); Guatemala: 1 male, " Guatemala ", " Sammlung Cl. Müller " ( ZSM); Costa Rica: 1 male, "C. Am. Costa Rica, Santa Rosa NP, Guanacaste, III.1993 leg. K.- G. Bernhardt " ( CLH); Surinam: 1 female, " Surinam 4-5", "alte Sammlung " ( ZSM); Guyana: 1 female, "B. Guinea Bartlett Coll. B.M. 1943-60." ( BMNH); Ecuador: 1 male, " Same Esmeraldas Ecuador ; 0 5.05.1997 leg. B. Hermann " ( CLH); Peru: 1 female, " Peru " ( BMNH); Brazil: 1 female, " Brasilia " ( BMNH); Venezuela: 1 female: " Venezuela (Guàrico) Cabruta nr. Caicara del Orinoco , 30m 07°38´N 66°15´W 20.VIII.2001 , S. Gottwald leg." ( CLH); 1 male: " Venezuela (Apure) ca. 50 km nördlich San Fernando d´Apure 20.VIII.2001 leg. O. Hillert " ( CLH); 1 male, " Venezuela / Bejuma-Carabobo (10.11 N-68.16 W), 800m, Via Palmichal / Finca Guarapito , 8.VII.1994 , Casa Maria, R. Ehrmann leg." ( CLH); Bolivia: 1 male, " Fertin Esteros Bolivia III.26 D. Chaco-Exped. ", " Megadytes giganteus Zim. " ( ZSM).

Descriptive notes. A description of this species was given by Sharp (1882) (as M. giganteus ). Here we provide photos of the habitus ( Figs 1B, E , 2B ) and focus on morphological characters of the male in different views ( Figs 8 A–C).The median lobe with both parameres is figured in ventral view ( Fig. 5A ), the tip of the median lobe in lateral view ( Fig. 5B ), and the median lobe in ventro-apical view ( Fig. 5C ).

Variability. Specimens from Venezuela and French Guyana differ from those of the type locality in Guadeloupe by: 1) habitus slightly broader and more convex; in lateral view maximum height situated a little more posteriorly; 2) in male, sexual pubescence on first mesotarsomere even more reduced, only present on proximal half of ventral midline ( Guadeloupe: along entire ventral midline); distal half with only large punctures but no setae; 3) protarsal disk slightly smaller; 4) base of prosternal process antero-ventrally a bit broader and more angulate ( Guadeloupe: more rounded); 5) parameres with transverse rugae more deeply impressed; apical region of median lobe in ventral view with lateral margins slightly less convergent and apex slightly broader. Further studies, including molecular work, will reveal whether Megadytes lherminieri is a species complex or not.

Distribution. The species is known from southern Mexico, Central America, Cuba, Puerto Rico, Caribbean, Venezuela, Bolivia, Peru, French Guyana, Surinam and the southern part of Brazil ( Blackwelder 1944; Trémouilles & Bachmann 1980; Ferreira-Jr. 1993; Blanco 2016). This is the first record of the species for Ecuador ( Fig. 11 ).

Habitat. All kinds of well-vegetated and permanent lentic sites such as larger swamps, ponds and oxbow lakes, farm dams and reservoirs. Ferreira (1993) collected the larvae in a sand dune swamp and several temporary ponds located in Maricá, Rio de Janeiro State, Brazil. Most records are from open and exposed sites and not in forested areas. Many specimens were collected at light. This species was sampled by one of us (MM) at 7 different localities in French Guyana and Guadeloupe ( Figs 9 , 10A ). All were permanent lentic water bodies of moderate to large size, with neutral to basic water, in open or semi-shaded situations. The bottom was moderately to heavily covered with organic substrata (decaying plant material) and the mineral substratum consisted of clay (3 sites) or was entirely composed of organic material (4 sites). The water was clear in three of the collecting sites and moderately to very turbid in the remaining ones. All places where M. lherminieri was found were characterised by rich vegetation, with hygrophytes in the surroundings of the water bodies and a more or less continuous belt of helophytes ( Cyperaceae and/or Poaceae ; Figs 9 , 10A ); in addition, angiosperms with floating leaves (such as Nymphaea ) were observed in 3/7 sites and all sites but one were densely colonised by submerged aquatic angiosperms. Four of the collecting sites clearly received substantial nutrients loads resulting from human activities and in one site the presence of Azolla was observed, indicating that M. lherminieri can tolerate some degree of anthropogenic eutrophication. From our field experience, the optimal micro-habitat for M. lherminieri is within dense belts of helophytes (e.g. Eleocharis and other large Cyperaceae , large Poaceae , etc.) at a moderate depth (e.g. 30 to 50 cm).

Biology. A female specimen (adult at the time of collecting) was kept alive in an aquarium for 3 years 9 months ( Fig. 10C ). As far as we know, this is the first record of a lifespan in Megadytes .

Figures

FIGURE 1. Habitus in dorsal view of: A) M. ducalis, B) M. lherminieri, C) M. magnus; habitus in ventral view of: D) M. ducalis, E) M. lherminieri (Ecuador, Esmeraldas), F) M. magnus (Paraguay, Cerro Lambaré).

FIGURE 2. Habitus in lateral view of: A) M. ducalis, B) M. lherminieri, C) M. magnus.

FIGURE 5. Megadytes lherminieri: A) median lobe with parameres in ventral view, B) tip of median lobe in lateral view, C) median lobe in ventro-apical view to show the flat tongue-like tip. Scale bars = 1.5 mm.

FIGURE 8. Megadytes lherminieri, male, Ecuador, Esmeraldas: A) ventral view of head, left protarsus and left middle leg, B) dorsal view of left protarsus, C) ventro-lateral view of left hind leg; M. magnus, male, Paraguay, cerro Lambaré: D) ventral view of head, right protarsus and right middle leg, E) dorsal view of left protarsus, F) ventro-lateral view of left hind leg. Scale bars = 5 mm.

FIGURE 9. Habitat of M. lherminieri in Guadeloupe: (A) Pond in Savane Desrosière, Anse Bertrand, Grande-Terre, Guadeloupe, 27.VIII. 2013, N16°30'09" W61°28'25"; (B) Pond near Sainte Anne, Grande-Terre, Guadeloupe, 17.VIII. 2013, N16°14'19"/W61°21'03.6" (Photos: M. Manuel).

FIGURE 10. Collecting method for M. lherminieri in Guadeloupe: (A) Close up view at Etang Fromager, Le Moule, Grande- Terre, Guadeloupe, 18 V 2012, N16°19'18"/W61°24'04"; (B) Example of a trap with Megadytes and other diving beetles inside (trapping session in the pond shown in Fig. 9A); (C) Female of M. lherminieri from Guadeloupe (Photos: M. Manuel).

FIGURE 11. Distribution of the subgenus Bifurcitus in Central and South America: White line: distribution of M. lherminieri; black line: distribution of M. magnus; red spot: only known locality for M. ducalis.