DYTISCIDAE, Leach, 1815

Arce-Pérez, Roberto & Novelo-Gutiérrez, Rodolfo, 2021, The Predaceous Diving Beetles (Coleoptera: Adephaga: Dytiscidae) from the Miradores Lagoon, Veracruz, Mexico, The Coleopterists Bulletin 75 (4), pp. 815-831 : 826-827

KEY TO THE SPECIES OF DYTISCIDAE OF MIRADORES LAGOON, VERACRUz, MEXICO

Note: Adapted from Arce-PÉrez and Roughley (1999), Balke et al. (2017), Biström (1996), Leech (1948), Leech and Chandler (1956), Miller (1998), Young (1963, 1979, 1980, 1981), and Zimmerman (1970, 1975).

1. Middle part of prosternum and prosternal process on the same plane ( Fig. 18 ). Pro- and mesotarsi 5-segmented, tarsomere 4 as long as tarsomere 3 ( Fig. 35 ). Scutellum exposed or concealed ............................. 5

1′. Middle part of prosternum and prosternal process not on the same plane, prosternal process at a lower level ( Fig. 19 ). Pro- and mesotarsi 4- or 5-segmented, tarsomere 4 smaller than tarsomere 3 (except Bidessonotus ) and partially covered by tarsomere 3 apical lobes ( Fig. 36 ). Scutellum generally concealed (exposed in Celina ) ( Hydroporinae ) .......... 2

2(1′). Scutellum exposed. Apex of elytra and last abdominal ventrite produced, elongate as a spine ( Fig. 2 ) ........... Celina AubÉ ............ 3

2′. Scutellum covered by pronotum.Apex of elytra rounded, subquadrate, or acute, but not elongate as a spine ................................... 4

3(2). Length 4–5 mm ( Fig. 2 ). Male genitalia with apical half of median lobe elongate, narrow, and apically sharp ( Fig. 20 ) .......... ................................ C. slossoni Mutchler

3′. Length 3.2–3.9 mm. Male genitalia with apical half of median lobe not narrowed apically, apex rounded ( Fig. 21 ) .....……… .................................... C. angustata Aubé

4(2). Metanepisternum reaching mesocoxal cavity ( Fig. 22 ); apex of prosternal process reaching metaventrite .............................. 5

4′. Metanepisternum not reaching mesocoxal cavity, separated from it by mesepimeron ( Fig. 23 ); prosternal process short, broad, and not reaching metaventrite …....……. ............................................ Vatellus Sharp a) Specimens dark reddish-brown, dorsal surface rough; length 5.5 mm. Pronotum evidently narrower than base of elytra; elytra darker with light marks along lateral margins ( Fig. 3 ) ............... ............................ V. mexicanus (Sharp)

5(4). Metacoxal process apically broad and trilobate: two narrow lateral lobes and a broad central lobe with a longitudinal depression ( Fig. 24 ). Small and strongly ovate specimens ( Fig. 4 ) .......................... Hydrovatus Motschulsky ........................................... 6

5′. Metacoxal process not trilobate, with or without lateral lobes; if lateral lobes present then covering base of metatrochanter. Large and not strongly ovate specimens, size and shape variable ........................... 7

6(5). Overall body coloration reddish-brown; black elytra with light reddish-brown oval markings and conspicuous lateral groove ( Fig. 4 ); length 3.2 mm, maximum width = 2.2 mm. Parameres (lateral view) subtriangular, apex broadly rounded, with a small process apically ( Fig. 25 ); parameres (dorsal view) with medial lobe gradually narrowing toward the apex ( Fig. 26 ) .................. H. youngi Biström

6′. Overall body coloration reddish-brown; elytra slightly darker than head and pronotum, without lateral groove; length 2.2 mm, maximum width = 1.5. Parameres (lateral view) subtriangular, apex narrow- ly rounded, without process apically ( Fig. 27 ); parameres (dorsal view) with median lobe abruptly narrowing toward the apex ( Fig. 28 ) ....................... H. davidis Young

7(5′). Metatibia almost straight, nearly uniform in width from base to apex ( Fig. 29 ); metatarsal claws unequal. Epipleuron with a diag- onal carina basally ( Fig. 31 ). Ovate ( Fig. 6 ) and ventrally convex beetles .................... 8

7′. Metatibia slightly arched, narrow in basal half, widening toward apex ( Fig. 30 ); metatarsal claws of equal length. Epipleuron without basal carina (except in Brachyvatus ). Elliptical beetles ( Figs. 7–11 ), not strongly convex ventrally.........................11

8(7). Mesocoxae separated by the width of one mesocoxa. Prosternal process short, broad, and with apex rounded ............ Pachydrus Sharp a) Specimens reddish brown; length 4.5 mm, width 2.5 mm; strongly convex ventrally; elytra dark ( Fig. 5 ) .............. .................................. P. politus Sharp

8′. Mesocoxae separated by half the width of one mesocoxa. Prosternal process rhomboid and with apex acute ............. Desmopachria Babington ….............................................. 9

9(8′). Length approximately 1.80 mm; color reddish-brown, elytra darker ..................... ................................... D. circularis Sharp

9′. Length approximately 2.6–2.7 mm ...... 10

10(9′). Metatibia with a serrated spine apically ( Fig. 32 ). Overall body coloration reddish-yellow. Elytra with markings as in Fig. 6 .............................. D. vicina Sharp

Figures

Figs. 18–28. Morphological structures of Dytiscidae. 18) Middle part of prosternum and prosternal process on the same plane (Laccophilinae, Copelatinae, Colymbetinae, Cybistrinae, Dytiscinae) (a: prosternal process); 19) Middle part of proster- num and prosternal process not on the same plane, prosternal process at a lower level (Hydroporinae) (a: prosternal process); 20)Apical half of median lobe of Celina slossoni; 21)Apical half of the median lobe of Celina angustata; 22) Metanepisternum (a) reaching mesocoxal cavity; 23) Metanepisternum (a) not reaching mesocoxal cavity; 24) Metacoxal processes apically broad and trilobite in Hydrovatini (a: lateral lobes; b: middle lobe); 25–26) Parameres in lateral and dorsal view of Hydrovatus youngi; 27–28) Parameres in lateral and dorsal view of Hydrovatus davidis. Figs. 18, 19, 22–24 taken from Arce-PÉrez and Roughley (1999); Figs. 20, 21 from Young (1979); Figs. 25–28 from Biström (1996).

Figs. 29–43. Morphological structures of Dytiscidae. 29) Metatibia almost straight; 30) Metatibia slightly arched; 31) Epipleuron with a transverse basal carina; 32) Metatibia with a serrated spur apically; 33) Head with a cervical stria; 34) Clypeus with medial transverse groove; 35–36) Pro- and mesotarsi in Bidessonotus and Liodessus; 37) Metatibial spurs bifid apically; 38) Male with metacoxal file; 39) Female ovipositor saw-like; 40) Female ovipositor rake-like; 41) Elytra, Laccophilus zimmermani; 42) Elytra, Laccophilus quadrilineatus tehuanensis; 43) Elytra, Laccophilus p. pictus. Figs. 29–31, 33, 35–40 taken from Arce-PÉrez and Roughley (1999); Fig. 41 from Arce-PÉrez and Morón (2017); Figs. 42–43 from Zimmerman (1970).

Figs. 2–9. Dorsal view of Dytiscidae. 2) Celina slossoni; 3) Vatellus mexicanus; 4) Hydrovatus youngi; 5) Pachydrus politus; 6) Desmopachria vicina; 7) Uvarus sp.; 8) Brachyvatus apicatus; 9) Neoclypeodytes moroni.