Megadytes parvus ( Tremouilles , 1984) Miller & Michat & Ferreira Jr, 2024

Miller, Kelly B., Michat, Mariano C. & Ferreira Jr, Nelson, 2024, Reclassification of Cybistrinae Sharp, 1880 in the Neotropical Region (Coleoptera, Adephaga, Dytiscidae), with description of new taxa, ZooKeys 1188, pp. 125-168 : 125

Megadytes parvus ( Tremouilles, 1984) comb. nov.

Figs 12 , 23 , 24 , 39-43 , 55

Cybister parvus Trémouilles, 1984: 187.

Type locality.

Brazil, Bahia State, Santa Rita.

Type specimens.

Holotype and nine paratypes in Museu de Zoologia, Universidade de São Paulo, Brazil and two paratypes, one male and one female, in Museo de La Plata, La Plata, Argentina.

Diagnosis.

This species differs from the other species in the genus, M. latus , in smaller size (TL = 13.0-14.6 mm), narrower shape (TL/GW = 1.9-2.1) (Fig. 12 ) and features of the male genitalia (Figs 39-43 ). See above under M. latus for details about these differences between the two species.

Description.

Measurements. TL = 13.0-14.6 mm, GW = 6.2-7.7 mm, PW = 5.4-5.9 mm, HW = 3.3-3.4 mm, EW = 2.0-2.1 mm, TL/GW = 1.9-2.1, HW/EW = 1.6-1.7, WC/WV = 4.1-4.8. Body shape elongate oval, widest slightly posteriad of middle; lateral margins broadly curved, continuously curved between pronotum and elytron (Fig. 12 ). Depressed and somewhat flattened in lateral aspect.

Coloration. Head dark green to green-rufous throughout. Pronotum dark green with broad lateral green-rufous margins. Elytron dark green with broad lateral green-rufous margins. Ventral surfaces dark rufous.

Sculpture and structure. Head broad, anteriorly produced, eyes prominent; dorsal surface evenly covered with extremely fine microsculpture and micropunctures. Pronotum with lateral margins evenly and broadly curved; surface similar to surface of head in microsculpture and micropunctation; pronotum somewhat swollen anteriorly. Elytron with margins very broadly curved; surface similar to surface of head in microsculpture, but with extensive, very fine micropunctation. Prosternal process anteriorly rounded, surface flat and broad, apex elongate and sharply pointed. Metaventral wing moderately broad, ~ 1/3 width of lateral portion of metacoxa; surface smooth, without sculpturing. Lateral portion of metacoxa large, broad, surface smooth, without sculpturing; metacoxal lines short, extending anteriorly less than half distance across metacoxa. Abdominal ventrites smooth, unsculptured.

Male genitalia. Male median lobe in lateral aspect broad throughout, subapically somewhat expanded, apically narrowed, apex with multiple small processes (Fig. 39 ); in dorsal aspect moderately narrow, evenly narrowed apically, apex narrowly lobed, ventral sclerite apically broadly lobed, extending to near apex (Fig. 40 ). Lateral lobe broad throughout length, evenly curved, apex rounded, with long series of setae along ventral margin (Fig. 41 ).

Female genitalia. The single female specimen available for examination lacks female genitalia which apparently have been dissected and lost.

Sexual dimorphism. Males have a broad protarsal palette with ventral adhesive setae with apical structures in the form of elongate flattened structures; males also have mesotarsomeres with posteroventral fields of setae. Females lack natatory setae along the ventral margins of the metatarsomeres, but these are present in males. Males and females each have unequal length metatarsal claws with the posterior shorter, but in males the posterior claw is relatively longer than in females, and distinctly, but only somewhat, shorter than the anterior (~ 4/5 of length).

Variation. Two paratype specimens were examined, a male and a female. The female has the extent and intensity of greenish-rufous coloration somewhat greater than the male, but otherwise the two specimens are similar.

Distribution.

This species is known only from Santa Rita, Bahia State, Brazil. I ndication by Trémouilles (1984) of the locality "Santa Rita" to Goyas State, Brazil is erroneous. In Brazil, there are several locations called Santa Rita, but in all labels of the type materials indicate "Santa Rita BA" in clear reference to Bahia State, Brazil (BA = abbreviation of Bahia) and not to Goiás State (= GO). “Goyaz” is an old spelling of Goiás State.

Habitat.

Nothing is known of the habitat of this species.

Material examined.

Twelve specimens in MZSP - holotype male and nine paratypes, six males and three females, each specimen labeled, "Santa Rita BA - Brasil IV.1958 E. Dente col. [label with black line border]/ Cybister (Cybister) parvus E. Tremouilles [handwritten] 1990 det. E. R. Tremouilles [label with black line border]/ Cybister (Meganectes) parvus . 1984 Tremouilles [red label, black line border, handwritten]". Holotype, one paratype female and the other paratypes respectively labeled, " Holotypus [red label, black line border], Holotypus [red label, black line border], Paratypes [label with black line border]"; two paratypes in MLP - one male and one female, each specimen labeled, "Santa Rita BA - Brasil IV.1958 E. Dente col. [label with black line border]/ Cybister (Cybister) parvus E. Tremouilles [handwritten] 1990 det. E. R. Tremouilles [label with black line border]/ PARATYPUS / MUSEO DE LA PLATA PARATIPO Cybister (Meganectes) parvus . 1984 Tremouilles [red label, black line border, handwritten]."

Figures

Figures 9 - 14. Neotropical Cybistrinae species, habitus 9 Cybister festae 10 Cybister puncticollis 11 Nilssondytes diversus 12 Megadytes parvus 13 Megadytes latus 14 species " IR 57 " (Ribera et al. 2008). Scale bar: 10.0 mm.

Figures 15 - 29. Neotropical Cybistrinae species, metatarsal claws and tarsomere VI of males and females 15, 16 Cybister festae 17, 18 Cybister puncticollis 19, 20 Nilssondytes diversus 21, 22 Megadytes latus 23, 24 Megadytes parvus 25 species " IR 57 " (Ribera et al. 2008) 26, 27 Paramegadytes glaucus 28, 29 Metaxydytes fraternus. Scale bars: 1.0 mm.

Figures 30 - 50. Neotropical Cybistrinae species, male genitalia 30 - 32 Cybister festae: 30 median lobe, right lateral aspect 31 median lobe, ventral aspect 32 right lateral lobe, right lateral aspect 33 - 35 Cybister puncticollis: 33 median lobe, right lateral aspect 34 median lobe, ventral aspect 35 right lateral lobe, right lateral aspect 36 - 38 Nilssondytes diversus: 36 median lobe, right lateral aspect 37 median lobe, ventral aspect 38 right lateral lobe, right lateral aspect 39 - 43 Megadytes parvus: 39 median lobe, right lateral aspect 40 median lobe, ventral aspect 41 right lateral lobe, right lateral aspect 42 apex of median lobe, right lateral aspect 43 apex of median lobe, ventral aspect 44 - 47 Megadytes latus: 44 median lobe, right lateral aspect 45 median lobe, ventral aspect 46 right lateral lobe, right lateral aspect 47 apex of median lobe, ventral aspect 48 - 50 species " IR 57 " (Ribera et al. 2008): 48 median lobe, right lateral aspect 49 median lobe, ventral aspect 50 right lateral lobe, right lateral aspect.

Figures 51 - 57. Neotropical Cybistrinae species, male sternite IX, ventral aspect 51 Cybister festae 52 Cybister puncticollis 53 Nilssondytes diversus 54 Megadytes latus 55 Megadytes parvus 56 Paramegadytes glaucus 57 Metaxydytes fraternus. Scale bars: 1.0 mm.