Melaenus Dejean 1831

Ball, George E. & Shpeley, Danny, 2005, Taxonomic review of the Tribe Melaenini (Coleoptera: Carabidae), with observations on morphological, ecological and chorological evolution, Zootaxa 1099 (1), pp. 1-120: 1-120

publication ID 10.11646/zootaxa.1099.1.1

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Melaenus Dejean 1831


Melaenus Dejean 1831  

Melaenus Dejean 1831: 481   . TYPE SPECIES: Melaenus elegans Dejean 1831   (by original designation).—Brullé 1835: 85.—Lacordaire 1854: 166.—Andrewes 1921: 184.—Péringuey 1926: 607.—Andrewes 1930: 212.Csiki 1933: 1651.Andrewes 1935: 26

Recognition. In general form, adults of Melaenus   ( Fig. 1A View FIGURE 1 ) resemble small platynines. However, they exhibit the features of the tribe Melaenini   (see above) and are recognized by the following combination of character states: overall size moderate (length ca. 8–10 mm); body form terete, subpedunculate; color black; dorsal surface subiridescent; mandibular scrobes each with one seta; head with single pair of supraorbital setae, pronotum with single pair of lateral setae; and elytra deeply, regularly striate, humerus projected anteriorly, subdentiform.

Description. Adult, with character states of tribe Melaenini   , and recognition features of Melaenus   , restricted and/or amplified as follows. Measurements of body. SBL more than 6.5 mm, and maximum width (EL) 2.5 mm or more ( Tables 3 and 4). Head relatively narrow, values for HW/PWM ( Table 5) less than 0.80. Elytra relatively long, values for PL/EL ( Table 6) 0.41 or less. Pronotum relatively narrow, values for PL/PWM ( Table 7) 0.84 or less, with base relatively broad (values for PWB/PWA ( Table 9) 0.78 or more.

Color of body black, elytra concolorous. Appendages: antennae piceous; labrum rufopiceous; mandibles, femora and tibiae black; palpomeres and galeomeres rufous; tarsi rufopiceous to rufous.

Microsculpture. Dorsal surface (head capsule, pronotum, scutellum, and elytra) generally with mesh pattern transverse, sculpticells very narrow, microlines microtrichiate ( Figs. 5B, 5F–G View FIGURE 5 ); mandibular scrobes ( Fig. 6I, f View FIGURE 6 ) and distal portion of middle tibia ( Fig. 7F View FIGURE 7 , ifs) with fimbriate sculpticells.

Luster. Body surface shiny, iridescent.

Macrosculpture. Head capsule with surface of frons and vertex generally moderately densely punctate, except clypeus smooth; ventral surface with anterior half laterally punctate like fronto­vertex, but median portion and all of posterior half of head capsule impunctate; or smooth with only elytral intervals punctate. Pronotum, proepisterna, proepimera and prosternum punctate like head, but proepipleura smooth. Abdominal sterna laterally punctate, like pronotum, but narrow medial area impunctate.

Vestiture. Body surface glabrous (except fixed sensory setae).

Fixed setae (body sclerites, mouthparts, elytra). Head capsule with one pair of clypeal setae and one pair of supraorbital setae; without row of long setae posteriad eyes. Mouthparts: mandible with single seta in scrobe ( Figs. 6A–D View FIGURE 6 , ss); glossal sclerite ( Fig. 7C View FIGURE 7 , gsc) with single pair of setae distoventrally. Elytron with parascutellar seta and lateral series. Abdominal sterna IV–VI without pair of ambulatory setae; sternum VII of males asetose; females with one pair setae near posterior margin, medially, inserted close together.

Head. Head capsule with dorsal surface posteriorly even, without pronounced transverse impression but with more or less distinct indentation posteriad eyes. Clypeus without dentiform projection medially on anterior margin.

Eyes ( Fig. 9 View FIGURE 9 ). Various: relatively large, values for OL/VW 0.31–0.44, or relatively small, values for OL/VW 0.22–0.33 ( Table 10).

Antennae ( Fig. 1A View FIGURE 1 ). Filiform, relatively long, extended distinctly posteriad pronotum. Antennomeres 1–4 (cf. Fig. 5A View FIGURE 5 ) with few setae, inserted near distal margin of respective articles; antennomeres 5–11 (cf. Fig. 5C View FIGURE 5 , ac, and 5D) densely, uniformly setose, except for narrow, shiny carina extended longitudinally on anterior and posterior surfaces; antennomeres evenly constricted proximally, not pyriform; antennomere 3 distinctly longer than antennomere 2, Ant 2 L/Ant 3 L 0.50 or less ( Table 11); antennomeres 5–10 about 2.5X longer than wide, slightly asymmetrical in form ( Fig. 5C View FIGURE 5 ); antennomere 11 similar in form to 5–10, but tapered distally to narrow apex.

Mouthparts. Labrum: apical margin slightly, evenly, to rather deeply subangularly concave. Epipharynx ( Fig. 6K View FIGURE 6 ) with pedium (ped) long, in form of equilateral triangle; extra parapedial setae (eps) laterad parapedial ridge (pr).

Mandibles. Left mandible in dorsal aspect ( Fig. 6B View FIGURE 6 ) with anterior retinacular tooth (art) evident. Right mandible ( Fig. 6C View FIGURE 6 ) in dorsal aspect with both retinacular teeth evident, but retinacular ridge concealed beneath terebral ridge.

Labium ( Figs. 7C–D View FIGURE 7 ). Paraglossae (pg) slender, narrow lobe, attached to glossal sclerite at base, only, surface without extensive covering of seta­like microtrichia.

Prothorax. Pronotum ( Fig. 1A View FIGURE 1 ) with lateral margins beaded; lateral grooves broad; posterior margin not beaded, flat; proepipleuron not evident in dorsal aspect; disc slightly convex, lateral declivity each side steep; posteriolateral angles acute, slightly projected.

Elytra ( Fig. 5E View FIGURE 5 ). Dorsal surface flat for most of length, apical declivity moderately steeply sloped; basal ridge narrow, extended to base of stria 5, not to edge of scutellum, anteriorly angulate; striae deep, distinct throughout length, punctate; intervals moderately convex.

Hind wings ( Fig. 8A View FIGURE 8 ). Macropterous. Wedge cell (w) large. Veins RP 3 + 4 and AA 3 + 4 present. Vein MP 4 more than half­length of MP 3.

Legs. Unguitractor plate ( Fig. 7G View FIGURE 7 , up) broad.

Abdominal sclerites. Sterna IV–VII narrowly transversely sulcate, posteriorly.

Male genitalia ( Figs. 8B–D View FIGURE 8 ). Endophallus with sclerite x ( Fig. 8B, x View FIGURE 8 ) large, more than half length of median lobe; parameres slender, elongate, with dense row of long setae distally ( Figs. 8C–D View FIGURE 8 ).

Ovipositor ( Figs. 7H–K View FIGURE 7 ). Laterotergite IX with anteriorly directed apophysis. Ramus about 0.80 length of gonocoxite 1. Gonocoxite 2 much shorter than gonocoxite 1 ( Fig. 7H View FIGURE 7 , gc1, 2), in lateral aspect ( Fig. 7I View FIGURE 7 ) with dorsal margins straight, not curved; broad in outline, distal margin broadly rounded ( Figs. 7J–K View FIGURE 7 ), ventral surface longitudinally rugulose ( Figs. 7I–K View FIGURE 7 ).

Female internal genitalia (Deuve 1993: 148, Fig. 222). Spermathecal duct shorter than spermathecal reservoir (sp), latter sausage shaped.

Included taxa. This genus includes two species, M. piger Fabricius   and M. elegans Dejean.  

Habitat. The members of Melaenus   occupy primarily the tropical deciduous forest/ savannah vegetation zone, but also desert/semi desert and tropical rain forest zones (Table 17 and Fig. 24).

Geographical distribution. The range of Melaenus   ( Fig. 10 View FIGURE 10 ), confined to the Eastern Hemisphere, is discontinuous, including only the Oriental Region, eastern Palaearctic Africa, and the central to northern parts of the Afrotropical Region, excluding the Congo Basin.

Relationships and chorological affinities. This genus is the more generalized putative adelphotaxon of Cymbionotum Baudi di Selve. The   geographical ranges of these genera overlap broadly in the Oriental Region, and in Africa (cf. Table 17).