Acyphus Heller

Lanteri, Analia A. & Rio, M. Guadalupe Del, 2006, Taxonomic revision of the monotypic genus Acyphus Heller (Coleoptera: Curculionidae) with comments on infraspecific variation, Zootaxa 1312, pp. 59-68 : 61-64

Acyphus Heller

( Figures 1–12 )

Acyphus Heller 1921:21 ; Dalla Torre et al. 1936:10 (catalogue); Emden 1944:513 (in key); Hustache 1947:8 (in key); Blackwelder 1947:792 (checklist); Wibmer & O’Brien 1986:52 (checklist); Alonso­Zarazaga & Lyal 1999:163 (catalogue).

Type species: Acyphus funicularis Heller 1921:27 (= Megalostylus renggeri Labram & Imhoff 1849 ), by original designation.

Diagnosis. Antenna robust, with scape strongly dilated and compressed from near base onwards; funicular article 2 as long as funicular article 1; remaining articles slightly longer than wide. Pronotum truncate­conical, thickened at base. Elytra somewhat depressed, with strongly bisinuate base, prominent humeri and 10 extra numeral striae (20 striae in total). Front tibiae with small denticles on inner face. Outer bevels broad, squamose. Spermatheca large, with long tubular nodulus and well developed ramus; spermathecal duct strongly sclerotized.

Redescription. Species medium sized (female 9.50–15.50 mm long; male 8.60–9.75 mm long). Integument either devoid of distinct scaly vestiture, or covered with recumbent short setae and cream, oval, apressed scales, forming an irregular nebulose pattern. Rostrum ( Figs 1–4 ) short to moderately long (LR/WR:1.15–1.33), moderately truncateconical (WF/WR:1.52–1.70), with elevate, sharp borders; dorsum flat, depressed on anterior third; median groove linear, deep, almost reaching anterior margin of pronotum; epistome narrow, covered with small oval scales; scrobes strongly curved, visible from dorsum, ending in front of eyes; gular angle about 90º. Mouthparts. Prementum ( Fig. 5 ) subcordate, external surface slightly concave, areolate, without setae; internal surface with a moderately developed median keel; palpi forming an obtuse angle regarding prementum. Maxillae ( Fig. 6 ) with subrectangular mala, almost parallel to axis of palpus, having three basal lacinial teeth and numerous setae; palpifer and articles 1–2 of palpi transverse, article 3 subconical. Eyes convex; preocular impression absent; postocular constriction slight. Frons and vertex slightly convex. Antennae ( Fig. 7 ) very stout; scape strongly dilated and compressed from near base onwards, reaching hind margin of eyes, as long as funiculum excluding club; funicular article 2 as long as article 1, articles 3 to 7 slightly longer than wide; club acuminate oval (LC/WC:1.75–2.20). Pronotum ( Figs 1–4 ) strongly transverse (WP/LP:1.37–1.57), truncate­conical (WP+/WP­:1.20–1.45); disc slightly convex, with median depression; front margin slightly curved onwards; flanks slightly arcuate; hind margin thickened, strongly bisinuate; posterior angles strongly projected. Scutellum distinct, small, covered with white scales. Elytra ( Figs 1–4 ) moderately elongate (LE/WE:1.48–1.68) and somewhat depressed; base strongly bisinuate; humeri strongly prominent, without tooth; apex entire (not bifid), moderately acute; apical declivity slight; punctures of striae moderate to broad; intervals slightly convex, having extra­numeral striae (whole number of striae= 20). Metathoracic wings present. Legs short; fore coxae contiguous, slightly closer to anterior margin than to posterior margin of prosternum; fore tibiae with row of 5 small denticles on inner face (crenulate) and strong mucro; tarsites 2 and 3 laterally expanded; outer bevels broad, squamose; dorsal comb slightly longer than apical comb. Abdomen. Intercoxal portion as long as cavities of hind coxae; ventrite 2 slightly longer than ventrites 3+4.

Female genitalia. Sternite VIII ( Fig. 8 ) subrhomboidal, 3x as long as apodeme, with pair of longitudinal strongly sclerotized stripes, apex curved bearing long setae. Ovipositor ( Figs 9–10 ) slender, long (about 0,6x as long as abdomen), slightly curved on lateral view, with 8–19 pairs of broad setae on external sides of distal half of baculi; hemisternites slightly sclerotized with short setae; baculi divergent toward proximal end; styli well developed, slightly divergent. Spermathecae ( Fig. 11 ) large (about 1mm), subcylindrical, with long tubular nodulus (as long as spermathecal body), well developed ramus, and long cornu with rounded apex; spermathecal duct strongly sclerotized.

Male genitalia. Aedeagus ( Figs 12–13 ) slightly shorter than abdomen; tube slightly longer than apodemes, slightly curved in lateral view, with subacute apex and large ostium.

Sexual dimorphism. Males more slender and smaller than females; antennal club more elongate and slender than in females (LC/WC:2.15–2.38); pronotum less transversal and larger in relation to elytral disc (values of LE/LP:2.97–3.20, smaller than in females), sides more arcuate on anterior third and less divergent towards posterior margin (WP/ LP:1.31–1.37, WP+/WP­:1.30–1.35); elytra more elongate than in females (LE/WE:1.67–1.84).

Geographic distribution and host plants. Acyphus ranges in north­central Argentina, southern Brazil, Paraguay and Uruguay. This area corresponds to the Chaco and Pampa provinces of the Chacoan subregion of the Neotropics, according to the biogeographic scheme of Morrone (2002, 2006). The Chaco (southern Bolivia, western Paraguay, southern Brazil and north­central Argentina) is a xerophyllous caducifolious forest; the Pampa (eastern Argentina, between 30º and 39º south latitude, Uruguay and southern part of the Brazilian state of Río Grande do Sul) is a savanna with Poaceae ( Morrone 2000) .

The only species of Acyphus seems to be associated to native trees of the Leguminosae family typical of the Chacoan subregion, especially Prosopis (Mimosoideae) , a genus that probably evolved within this xeric biogeographic unit ( Roig 1993), playing an important role in the plant­herviborous interactions (Solbring 1977). The known hosts are Prosopis affinis Sprengel (= Prosopis algarrobilla , Prosopis nandubay ), Prosopis torquata and Thalia sp. Prosopis affinis is a late deciduous tree, up to 8 m high, distributed in northeastern Argentina (Buenos Aires, Chaco, Córdoba, Corrientes, Entre Ríos, Formosa, Santa Fe and Santiago del Estero provinces), southern Bolivia, southwestern Brazil, Paraguay, Peru and Uruguay ( Burkart 1978). This area approximately corresponds to the geographic distribution of Acyphus .

Remarks and comparative notes. Nothing is known about the possible relationships of Acyphus with other genera of Naupactini . In the keys of Heller (1921), Emden (1944) and Hustache (1947) it goes out in the same couplet as Cyrtomon Schoenherr (senior synonym of Cyphus Germar and Neocyphus Bedel ) (see Lanteri 1990 a), based on the presence of supernumerary striae, however, in Cyrtomon these striae are not present in every interval (14 striae in total) and they are not continuous from base to apex. On the contrary, Acyphus has 20 complete striae being impossible to distinguish regular to supernumerary ones. Other external features such as those of the vestiture, the proportion of the antennal articles, and the shape of the body (especially pronotum and elytra) are clearly different in both genera.

We propose that Acyphu s is more closely related to Cyphopsis Roelofs , also ranging in the Chacoan subregion. Both genera are similar in the characters of the antenna, body shape and vestiture (color, shape and arrangement of scales and setae). The type species of Cyphopsis , C. clathrata Roelofs , shows an elytral nebulose pattern similar to that seen in Acyphus (see Lanteri & del Río 2006). The main external differences between Acyphus and Cyphopsis are the presence of 20 elytral striae (instead of 10 normal striae), the absence of tubercles on pronotal flanks and the lack of denticles on the inner margin of all tibiae.

Based on male genitalia, Acyphus is also more closely related to Cyphopsis than to Cyrtomon , because in the latter genus the aedeagal apex has a particular arrow pointed shape similar to that of Priocyphus Hustache and Mendozella Hustache (see Lanteri 1989, 1990 b; Lanteri & Morrone 1991), whereas in Acyphus and Cyphopsis is subacute. Regarding to the female genitalia, all these genera are characterized by a strongly sclerotized spermathecal duct and a large spermathecae, with well developed ramus and long tubular nodulus. The curvature of the nodulus, the shape of the sternite VIII (subrhomboidal and with a long apodeme) and most characters of the ovipositor approximates Acyphus to Cyrtomon , more than to Cyphopsis . However, in Acyphus there is a very distinct feature of the ovipositor not seen in the other genera, the presence of two rows of coarse setae on each side of the baculi, the latter being recorded for some Naupactus Dejean. For an accurate phylogenetic placement of Acyphus it will be necessary to undertake a complete phylogenetic analysis of all the Naupactini genera, which is the main goal of our research.

Figures

FIGURES 1 – 4. Dorsal habitus of Acyphus renggeri. 1 – 3, females; 4, male. Scale: 2 mm.

FIGURES 5 – 13. Mouth­parts, antennae and genitalia of Acyphus renggeri. 5, prementum, external surface; 6, maxilla; 7, antennae; 8, sternite VIII; 9 – 10, ovipositor, ventral and lateral; 11, spermathecae; 12 – 13, aedeagi, ventral and lateral. Scales: 1 mm (antennae); 0.5 mm (sternite VIII, ovipositors and aedeagi); 0.25 mm (mouth­parts, spermathecae).