Mecocephala acuminata Dallas, 1851

de Barros, Lurdiana Dayse, Barão, Kim Ribeiro & Grazia, Jocelia, 2022, Taxonomic updates on the Mecocephala group (Hemiptera: Pentatomidae): redescription of Mecocephala Dallas and Paramecocephala Benvegnú, Journal of Natural History (J. Nat. Hist.) 55 (43 - 44), pp. 2691-2747 : 2698-2705

Mecocephala acuminata Dallas, 1851

( Figures 1a , 2a , 3a–d , 4a–h , 9a–c , 10a, d , 29 ; Table 1)

Mecocephala acuminata Dallas, 1851: 180 ; Stål 1872: 30; Berg 1884: 25; Lethierry and Severin 1893: 132; Kirkaldy 1909: 71; Schwertner et al. 2002: 175–177, figs 2, 7, 12, 17, 22–24, 31, 35; Grazia and Schwertner 2008: 234; Coscarón 2017: 227; Barão et al. 2017: table 1; Barros et al. 2020b: 351, tables 1, 2.

Mecocephala holmbergi Pirán, 1969: 138 ; Pirán 1970: 126; Grazia 1986: 52 [syn. nov.]; Schwertner et al. 2002: 175–177.

Type material. URUGUAY: MONTEVIDEO: Holotype, f*, Type, a, M[onte]video [Uruguay], Brit[ish] Mus[eum] type no. Hem–058 // Holotype Mecocephala acuminata // Presented by Charles Darwin (NHMUK).

Type material examined. ARGENTINA: BUENOS AIRES: Holotype, f*, Tandil , December 1957, [Raul J.] Llano leg. // ‘Holotypus̍ // ‘ Mecocephala holmbergi , 1969, det. A.A. Pirán̍ ( MACN) .

Other material examined. ARGENTINA: BUENOS AIRES: m*, Mar del Plata , 22 December 1919, A. Frers leg. ( UFRG) ; f*, G[eneral] Alvarado , 18 November 1986, Bachmann leg. <female illustrated> ( MACN –2990) ; f*, Las Flores , 29 June 1931 ( MACN –27664) .

No data: m* <male illustrated> ( UFRG).

Diagnosis. Body colour brown. Anteocular processes present. Antennomere 3 slightly flattened dorsally. Bucculae sinuous. Proportions of labiomeres 1 <2> 3 <4. Outline of anterolateral margins of pronotum smooth, not punctate. Median furrow of each peritreme of ESES short, reaching less than half of peritreme; outer margin of metapleural evaporatorium convex; metathoracic spiracles wide ( Figure 3a–d ). Spiracles of abdominal sternite 2 covered by metathorax.

Male genitalia. Pygophore sub-rectangular ( Figure 4d–g ). Posterolateral angles acute. Superior layer of ventral rim with two pairs of processes ( Figure 4e–f ). Inferior layer of ventral rim with a pair of processes ( Figure 4g ). Phallus ( Figure 9a–c ): Phallotheca shorter than wide apically; dorsal processes of phallotheca wider apically than medially. Conjunctiva with a pair of processes, each acute apically, and two pairs of lobes: median and ventral, membranous. Ductus seminis distalis extremely long in relation to length of conjunctiva.

Female genitalia. Valvifers 8 smaller than the laterotergites 9; posterior margins arcuate. Posterior margins of laterotergites 8 obtusely projected. Laterotergites 9 triangular, obtusely projected apically. Valvifers 9 flat, anterior margins concave, posterior margins straight ( Figure 4h ). Proximal ductus receptaculi at least three times longer than the length of vesicular area, and constant diameter along its length. Median wall of vesicular area enlarged subproximally. Distal ductus receptaculi convoluted, long, at least two times longer than vesicular area, same diameter as the diameter of the median wall of vesicular area. Annular flanges parallel to each other ( Figure 10a, d ).

Measurements. See Table 1.

Remarks. Mecocephala acuminata differs from its congeners by the outer margins of evaporatorium convex, posterolateral angle of pygophore acute, superior layer of ventral rim of pygophore with two pairs of processes, phallotheca wider apically than medially, valvifers 8 smaller than laterotergites 9, posterior margin of valvifers 9 straight, distal ductus receptaculi at least two times longer than vesicular area.

Distribution. Argentina (Buenos Aires, Mar del Plata, and Alvarado/Miramar) and Uruguay (Montevideo) ( Figure 29 ).

Figures

Figure 1. Head and pronotum of Mecocephala in dorsal view. (a) Mecocephala acuminata; (b) Mecocephala bonariensis; (c) Mecocephala curculionoides; (d) Mecocephala magna; (e) Mecocephala maldonadensis; (f) Mecocephala zikani. Scale bars = 0.5 mm.

Figure 2. Head and prothorax of Mecocephala in lateral view. (a) Mecocephala acuminata; (b) Mecocephala bonariensis; (c) Mecocephala magna; (d) Mecocephala maldonadensis; (e) Mecocephala zikani. Scale bars = 0.5 mm.

Figure 3. Thoracic external scent efferent system (ESES) of metasternal glands of Mecocephala. (a–d) Mecocephala acuminata; (e–g) Mecocephala bonariensis; (h) Mecocephala magna. (a–h) mesopleuron and metapleuron in ventral view; (b–g) scanning electron microscopy images of characters of ESES of metasternal glands. Abbreviations: cx2 – mesocoxe; cx3 – metacoxae; ev – evaporatorium; ms – mesopleuron; mt – metapleuron; mts – metathoracic spiracle; o – ostiole; om – outer margin; pod – periostiolar depression. Scale bars: a, h = 0.5 mm; b, e = 500 µm; c–d, f–g = 200 µm.

Figure 4. Mecocephala acuminata Dallas, 1851. (a–c) Habitus in dorsal, ventral and lateral view; (d–g) pygophore in dorsal, posterior, ventral and lateral view; (h) genital plates in posteroventral view. Abbreviations: alvr – area between layers of ventral rim; dr – dorsal rim; ilvr – inferior layer of ventral rim of pygophore; la8 – laterotergites 8; la9 – laterotergites 9; pilvr – process of inferior layer of ventral rim; pslvr – process of superior layer of ventral rim; slvr – superior layer of ventral rim of pygophore; vf8 – valvifers 8; vf9 – valvifers 9; vr – ventral rim; x – segment X. Scale bars: a–c = 2.0 mm; d–h = 1.0 mm. (Parameres and segment X not shown).

Figure 9. Phallus of Mecocephala species in dorsal (left column), lateral (center column) and ventral (right column) views. (a–c) Mecocephala acuminata; (d–f) Mecocephala bonariensis; (g–i) Mecocephala magna. Abbreviations: aa – articulatory apparatus; cj – conjunctiva; dc – dorsal connective; dpph – dorsal process of phallotheca; mlcj – median lobe of conjunctiva; pcj – process of conjunctiva; pdpph – posterodorsal projection of phallotheca; ph – phallotheca; plpph – posterolateral projection of phallotheca; pve – process of vesica; vbpph – ventrobasal projection of phallotheca; vlcj – ventral lobe of conjunctiva. Scale bars = 1.0 mm.

Figure 10. Female receptaculum seminis and aussenwand of Mecocephala species. (a, d) Mecocephala acuminata; (b, e) Mecocephala bonariensis; (c, f) Mecocephala magna. Abbreviations: aaf – anterior annular flanges; cs – capsula seminalis; ddr – distal ductus receptaculi; paf – posterior annular flange; pdr – proximal ductus receptaculi; pi – pars intermedialis; rs – ring sclerites; tvi – thickening of vaginal intima; va – vesicular area. Scale bars = 1.0 mm.

Figure 29. Map showing the geographical distribution of Mecocephala and Paramecocephala species. Yellow star = new record of P. subsolana.