Megymenum tuberculatum Hemala & Kocorek, 2020

Hemala, Vladimír, Kocorek, Anna & Lis, Jerzy A., 2020, Megymenum tuberculatum, a new species of Megymenini from Java and a review of distribution of M. brevicorne (Hemiptera: Heteroptera: Dinidoridae), Zootaxa 4808 (3), pp. 439-454 : 440-441

Megymenum tuberculatum Hemala & Kocorek , sp. nov.

( Figs 1–3 , 5 , 13 )

Type locality. Indonesia, Java .

Type material. Holotype: ♀ ( MHNG), INDONESIA: Java: ‘418 / 65 Java. / M. Melly.’ [hw, ivory label] // ‘ ♀ ’ [p, small white label] // ‘ HOLOTYPUS / Megymenum / tuberculatum / sp. nov. / det. V. HEMALA & A. KO- COREK 2017 [p, red label]’. The holotype is card-mounted, with a pin-hole in pronotum and right hemelytra; right basi- and distiflagellum, left antenna, labial segments III and IV, right and left protarsal segments II and III, right middle leg, and right hind leg all missing.

Description of female (holotype).

Coloration ( Figs 1–3 ). Body dark brown, only labium light brown and membranes of hemelytra yellowish with dark brown spots at the base. Small fields around abdominal trichobothria are also light brown.

Punctation. Head, anterior pronotal tubercle, posterior pronotal lobe, scutellum, clavus, connexiva and abdominal laterotergites with small, dense punctures. Punctation of anterior pronotal lobe, ventral sides of pro-, meso- and metathorax and abdominal ventrites with lower density.

Pilosity. The vast majority of the body surface without pilosity, only very small areas around coxae and a shallow depression between valvifers VIII and laterotergites IX covered by sparse and very fine light brown colored hairs at their anterior sides. All tibiae apically covered with small semierect setae. Ventral side of tarsi covered by very fine and very dense setae forming a pillow.

Structure. Body medium sized, elongate ( Fig. 1 ), widest across mid of abdomen (between apices of lobes on laterotergites IV), only slightly convex dorsally, strongly convex ventrally, thorax trapezoid in cross section ( Fig. 5 ).

Head slightly wider than long; clypeus very small, mandibular plates longer than clypeus, together heart-shaped and strongly concave dorsally. Anteocular spines large, triangular but not sharp. Base of head wide (widest across eyes); small compound eyes positioned posterolaterally, nearly in touch with anterior part of pronotum. Antenniferous tubercle very small, short and not visible in dorsal view. Anteocular processes present and visible from dorsal view. Scape (I) very short, shorter than mandibular plate; pedicel (II) nearly flattened, 2.5 times longer than segment I and longer than mandibular plate. Basi- (III) and distiflagellum (IV) mutilated. Bucculae round, very short, but longer than labrum. Labial segment I shorter than segment II, clearly reaching posterior margin of head, segments III and IV mutilated.

Thorax. Pronotum ( Figs 1 , 5 ) trapezoid in dorsal view, without well differentiated collar-like structure.Anterior margin of pronotum slightly concave; anterolateral margin only very slightly projecting forward to form very small and rounded process, only very slightly concave anteriad from this process and nearly straight posteriad from this process. Posterolateral margin slightly rounded, as long as 2/3 of anterolateral margin; posterior margin along base of scutellum slightly convex. Pronotal surface tuberculate, with very large rounded tubercle in the middle of its anterior part, positioned at the anterior margin. This tubercle is 1.4 times wider than long. Disc with depressions at anterolateral angles. Scutellum only slightly longer than wide at its base, reaching about middle of abdominal length; regularly narrowing posteriad. Prosternum with tubercles around the coxae, meso- and metasternum nearly flat, without tubercles. External scent efferent system with large ostiole and evaporatorium. Ostiole positioned nearly in ventral 1/4 of metapleuron. Peritreme in form of short, narrow spout (about twice as long as ostiole), directed slightly posterolaterad with rounded apex. Evaporatorium wide, placed on the strongly folded cuticle, covering the lateral 1/3 of vestibulum, central part of metepisternum anteriorly (in shape of wide semicircle) and narrow strip in central part of mesepimeron posteriorly, surrounding the whole peritreme and nearly the whole metathoracic spiracle. Metathoracic spiracle narrow, straight, placed in the middle of suture between meso- and metapleuron.

Hemelytra. Clavus short, slightly surpassing half-length of scutellum. Corium slightly shorter than scutellum, lacking apparent veins; anterodistal (seemingly posterolateral) angle rounded. Membrane large, twice as long as clavus; apically widely rounded, reaching apex of abdomen. Venation on membrane reticulate.

Legs. Pro- and mesofemur clavate and shorter than metafemur, metafemur rather cylindrical and longer than pro- and mesofemur. Mesofemur 1.22 times longer than profemur, and metafemur 1.23 times longer than mesofemur. Profemora with two longitudinal series of denticles after four denticles on ventral side apically. Mesofemur and metafemur with two longitudinal series of denticles after three denticles on ventral side apically. Length of dencticles on femora gradually increased towards apex. Femora apically flat between the rows of denticles. Pro- and mesotibia shorter than metatibia, metatibia longer than pro- and mesotibia and bearing the tympanal organ (seen in Dinidoridae females only). Mesotibia 1.13 times longer than protibia, and metatibia 1.44 times longer than mesotibia. Tarsi 3-segmented; protarsal segments II and III mutilated.

Abdomen. Connexiva not covered by hemelytra; posterolateral angles of connexival segments with two distinct small lobes on each one segment, of which anterior one very small, posterior one larger and well developed. Spiracle II exposed, situated slightly more ventrally than spiracles III–VIII. Spiracle VIII clearly smaller than spiracles II–VII, and positioned more laterally on laterotergite VIII. Two trichobothria situated on each laterotergite III–VII, postspiracular, the anterior one positioned more laterally, the posterior one more ventrally; each trichobothrium situated in separate small field.

External female genitalia. Valvifers VIII of quarter-circular shape, not fused medially; laterotergites IX trapeziform.

Spermatheca ( Fig. 13 ). Apical receptacle (spermathecal bulb) spherical, medium sized. Intermediate part (pumping region) short, well defined, with distinct and large distal and proximal flanges. Spermathecal duct large, strongly dilated (sac-like), with a distinct lateral fold bearing inconspicuous ring sclerite. Spines of spermathecal duct distinct and large, covering only a small L-shaped area postero-lateraly of the ring sclerite.

Measurements (of holotype, in mm; n = 1). Body length (from apex of clypeus to apex of abdomen) 13.18; head: length (from apex of clypeus to anterior margin of pronotum) 2.01, width (maximum width across eyes) 2.56, height (height across compound eye) 1.62, interocular width (between inner margins of compound eyes) 1.78; lengths of antennal segments: scape (I)—0.85, pedicel (II)—1.71, basiflagellum (III)—?, distiflagellum (IV)—?; length of labial segments: I—1.32, II—1.40, III—?, IV—?; pronotum: length (medially) 3.72, anterior width (between anterolateral angles) 4.65, length of anterior tubercle (medially) 1.24, width of anterior tubercle (in middle) 1.74; posterior width (maximum width between humeral angles) 5.97; scutellum: length (medially from base to apex) 3.87, width (maximum width at base) 3.41; corium: length 4.03, width 1.86; abdomen width (maximum width between apices of lobes on laterotergites IV) 7.32; length of femora: profemur 2.79, mesofemur 3.41, metafemur 4.18; length of tibiae: protibia 2.48, mesotibia 2.79, metatibia 4.03; length of tarsi: protarsus?, mesotarsus 1.24, metatarsus 1.24.

Male. Unknown.

Differential diagnosis. The habitus of M. tuberculatum sp. nov. is very similar to that of M. brevicorne ( Fabricius, 1787) (see Figs 1, 4 ), but the new species differs in the characters on head, antennae, pronotum, prosternum, connexiva and spermatheca. The crucial character for separating the new species is distinctly larger anterodorsal tubercle on pronotum, but in contrast to M. brevicorne , the new species has also: i) anteocular spines on head present (only sporadically found in M. brevicorne ; see Figs 1, 4 ), ii) pedicel more wider and more flattened, iii) pronotum with not well differentiated collar-like structure due to the low concavity of its anterolateral margin (see Figs 5, 6 ), iv) prosternum with tubercles around the coxae (not present in M. brevicorne ), v) connexiva with smaller and not so sharp lobes as in M. brevicorne (see Figs 1, 2, 4 ), vi) intermediate part (pumping region) of spermatheca clearly shorter than in M. brevicorne (see Figs 13, 14 ), vii) spermathecal duct slightly shorter and more dilated lateraly than in M. brevicorne (see Figs 13, 14 ), viii) slightly more distinct lateral fold of spermathecal duct, but inconspicuous ring sclerite (slightly less distinct lateral fold and more distinct ring sclerite in M. brevicorne ; see Figs 13, 14 ) and ix) L-shaped spine area of spermathecal duct (only longitudinal in M. brevicorne ; see Figs 13, 14 ). Anterodorsal tubercle on pronotum of the new species is the largest among all known species of the genus Megymenum which possess this tubercle ( Figs 5–12 ).

Etymology. The species name is the Latin adjective tuberculatum (= tuberculate), referring to the characteristic large anterodorsal tubercle of pronotum, which is distinctly larger than such tubercle in all other known species of the genus.

Biology. Unknown.

Distribution. Indonesia: Java (without exact locality).

Note on collector name. The collector name “M. Melly” written on the first ivory label probably refers to André Melly (1802–1851) who gathered a large entomological collection in MHNG (over 22 000 species from around the world) consisting especially of beetles ( Coleoptera ), but also of other insect orders (viz Schaum 1852).

Figures

FIGURES 1–4. Habitus of Megymenum tuberculatum Hemala & Kocorek, sp. nov. and M. brevicorne (Fabricius, 1787). 1–3—female of M. tuberculatum (1—dorsal view, 2—ventral view, 3—lateral view); 4—female of M. brevicorne (dorsal view). Black arrows show the position of anteocular spine/tubercle. (Photo: V. Hemala).

FIGURES 5–12. Visual comparison of pronotum shape and size of dorsal anterior tubercle in eight species of the genus Megy- menum Guérin-Méneville, 1831. 5—Megymenum tuberculatum Hemala & Kocorek, sp. nov.; 6—M. brevicorne (Fabricius, 1787); 7—M. basale Walker, 1868; 8—M. parallelum Vollenhoven, 1868; 9—M. spinosum (Burmeister, 1834); 10—M. mekon- gum Distant, 1921; 11—M. pratti Distant, 1911; 12—M. gracilicorne Dallas, 1851. (Photo: V. Hemala).

FIGURES 13–14. Spermatheca. 13—Megymenum tuberculatum Hemala & Kocorek, sp. nov.; 14—M. brevicorne (Fabricius, 1787). Abbreviations: ar—apical receptacle (spermathecal bulb), dfl—distal flange, ip—intermediate part (pumping region), pfl—proximal flange, s—spines, sd—spermathecal duct, rs—ring sclerite. Scale bars: 0.5 mm. (Orig. A. Kocorek).