Minyomerus [JF2015] Horn, 1876 sec. Jansen & Franz (2015)

Jansen, M. Andrew & Franz, Nico M., 2015, Phylogenetic revision of Minyomerus Horn, 1876 sec. Jansen & Franz, 2015 (Coleoptera, Curculionidae) using taxonomic concept annotations and alignments, ZooKeys 528, pp. 1-133 : 9-15

Taxon classification Animalia Coleoptera Curculionidae

Genus Minyomerus [JF2015] Horn, 1876 sec. Jansen & Franz (2015)

> Minyomerus Horn, 1876: 17 sec. Horn (1876)

> AND = Elissa Casey, 1888: 271 sec. Casey (1888) (synonymized by Kissinger 1964: 30)

> AND = Pseudelissa Casey, 1888: 273 sec. Casey (1888) (synonymized by Pierce 1909: 359)

> AND = Piscatopus Sleeper, 1960: 84 sec. Sleeper (1960), syn. n.

Type species.

Minyomerus microps (Say, 1831: 9) sec. Jansen & Franz (2015), stat. n.

== (INT) AND> (OST) AND = Thylacites microps Say, 1831: 9 sec. Say (1831) (transferred to Minyomerus sec. Blackwelder & Blackwelder [1948] on the authority of Buchanan in litt. by Blackwelder and Blackwelder 1948: 46)

== (INT) AND> (OST) AND = Thylacites microsus Boheman, 1833: 523 sec. Boheman (1833) (synonymized by LeConte 1859: 286)

== (INT) AND> (OST) AND = Minyomerus innocuus Horn, 1876: 18 sec. Horn (1876) (type, designated by Pierce 1913: 400), syn. n.

Diagnosis.

Minyomerus [JF2015] is diagnosed by a unique combination of synapomorphic traits; specifically, the integument is covered by appressed scales that are sub-circular and overlap posteriorly; the nasal plate is present as a broad, scale-covered, chevron-shaped ridge demarcating the epistoma; a sulcus posteriad of nasal plate is present; the scrobe is subequal in length to the funicle and club combined; the head is directed slightly ventrally; the metatibial apex lacks setiform bristles yet displays bristles that are shorter to subequal in length to the surrounding setae and conical to lamelliform; the mesotarsi are slightly shorter than the mesotibiae, and all tarsi lack pads of setiform setae but have stout, spiniform setae. The following additional characters are useful for identifying members of Minyomerus [JF2015], especially when differentiating the former from other genera of Tanymecini [non-focal] such as Isodrusus Sharp, 1911 [non-focal], Isodacrys Sharp, 1911 [non-focal], and Pandeleteinus Champion, 1911 [non-focal] (see also Anderson 2002): the intercoxal process of the prosternum is medially divided into two halves (with the procoxae apparently contiguous in most); the elytral humeri are rounded rather than angled and protruding; the profemora are not dilated and lack spines; the protibiae are ventrally excavated by a longitudinal groove or concavity; and a distinct scrobe is present and directed ventrad of the eye, with a more or less apparent tooth formed by an overhang of the dorsal margin.

Description - female.

Habitus. Length 2.80-6.49 mm, width 1.02-2.41 mm, shape elongate and sub-cylindrical, length/width ratio 2.18-2.94 mm, widest at anterior 1/5-2/5 of elytra. Integument tan to black, vestiture consisting of appressed sub-circular to occasionally irregular squamiform scales, arranged densely throughout, partially overlapping; color and opacity varying among species, from white to dark brown, though generally brownish, in some species appearing semi-translucent (in others opaque), metallic, or opalescent; with interspersed colors forming small maculae, bands and other variously scattered patterns; scales generally becoming lighter ven trally, including rows of setae. Linear setiform scales ( ‘setae’) sparse throughout, short, sub-erect to sub-recumbent, brown to white, arranged in rows on elytral intervals, and becoming longer on humeri and venter.

Mouthparts.Mandibles. Covered with non-overlapping, sub-circular to sub-quadrate, whitish or opalescent scales, with several setae; ovate scar from deciduous process located apicolaterally.

Maxillae (Fig. 10B). Cardo as long as distance from base of palpomere I to base of palpiger, wider than palpomere III, bifurcate at base with an inner angle typically between 90-120°, arms of variable length, inner (mesal) arm thicker than outer arm in most species, apical end strongly curved outward (laterally) at a 90° angle, one or both arms of bifurcation equal in length to apically outcurved arm, glabrous. Stipes short, sub-quadrate to sub-rectangular, roughly equal in length to one or both bifurcations of cardo, glabrous or with a single lateral seta. Galeo-lacinial complex not extending to apex of maxillary palpomere I, apically rounded; complex membranous and setose in posterior 1/2-3/4, sclerotized and somewhat emarginate anteriorly; dorsally with 5-9 apicomesal lacinial teeth; ventrally with 1-5 reduced lacinial teeth. Palpiger with a transverse row or patch of setae; anterior portion variably membranous, posteriorly sclerotized. Maxillary palps three-segmented; I longer than II, I apically oblique, apical end facing mesally and forming 30-60° angle with base, I and II with variably inserted setae; II shorter than III; III elongate, with parallel sulci and apical sensilla.

Labium (Fig. 10A). Prementum completely covering maxillary palps; often pentagonal or hexagonal, ventrally sub-planar, concave laterally; margins of prementum with variable degrees of curvature, apicomedially projected (ligula), ligula angulate; each lateral region with 1 long seta. Labial palps 2- or 3-segmented, variably exposed; II shorter than I, both usually with 1 apical seta; III similar in length to II, when present; III apically constricted and with sensilla.

Rostrum. Length 0.38-0.83 mm, appearing markedly reduced in length, anterior portion variably broader than long, sub-equal in width to head, rostrum/pronotum length ratio 0.41-0.75, rostrum length/width ratio 0.73-1.43; shape in cross section sub-rectangular for most species. Separation of rostrum from head generally obscure; rostrum sub-divided into a short, planar, transverse, anterior section, and a larger, convex, posterior section with a seamless transition into rest of head. Dorsal outline of rostrum square to trapezoidal, anterior half of dorsal surface mesally planar, posterior half convex and rugoso-punctate. Rostrum in lateral view nearly elongate-rectangular to square; basal half of dorsolateral margins converging anteriorly, anterior half sub-parallel; apical margin emarginate and bisinuate, with 2-6 large vibrissae, each inserted laterad of each sinuation. In frontal view, nasal plate defined by V-shaped or Y-shaped, impressed lines, concave to convex, integument covered with non-overlapping sub-circular white or opalescent scales, and with interspersed apically directed setae. Margins of mandibular incision straight, slightly diverging dorsally in frontal view, bounded by same type of scales as those on nasal plate. Ventrolateral sulci variably defined as a deep notch or sulcus dorsad of insertion point of mandibles, running parallel to the scrobe. Dorsal surface of rostrum with median fovea at posterior end of nasal plate; ventro lateral margins sub-parallel. Rostrum ventrally with a median fovea and 2 sub-parallel sulci beginning at corners of oral cavity and continuing as small foveae towards base of rostrum; with 2 foveae laterad of former and roughly in line with insertion point of mandibles; these sulci and foveae can be variably expressed. Oral cavity with lateral margins nearly straight (Fig. 6A).

Antennae. Antennal insertion near apical 1/3 of rostrum, dorsal to posterior margin of mandibular insertion point. Scrobe lateral, strongly curved, with parallel edges nearly continuing to anterior margin of eye; dorsal margin of scrobe overhanging slightly and forming a minute tooth, variably located relative to eye. Antennae apparently 12-segmented, segment 11 with annulus that lacks an inner phragm. Scape slender, clavate; directed ventrad of eye in idealized position; covered with appressed, squamiform scales with interspersed setae on clubbed section of scape. Funicle 7-segmented; sub-equal in length to scape; funicular antennomeres progressing from elongate to equilateral, clavate, covered with appressed scales and apically directed, interspersed setae; segments becoming less clavate and shorter with increasing proximity to club, except for terminal segment, which is longer and wider than preceding segment; where noted, some species without scales on terminal segment, clothed as antennal club. Club appearing 4-segmented, terminal segment with annulus that lacks an inner phragm; similar in length to funicular antennomeres III-VII, 2.5-3.0 × as long as wide, with a covering of apically-directed pubescence with interspersed sub-erect setae.

Head. Eyes small, laterally positioned, globular, coarsely facetted, protruding, anterodorsal margin of each eye impressed, posterior margin elevated from lateral surface of head; eyes separated in dorsal view by 3-6 × their anterior-posterior length, set off from anterior prothoracic margin by up to 1/2 of their anterior-posterior length. Head between eyes rugose and bulging. Head typically with a broad, transverse post-ocular impression.

Thorax.Pronotum. Variously equilateral (with dimensions of dorsal, lateral, and ventral surfaces equal, or nearly so), length/width ratio 0.68-1.06, surface transversely convex, sub-cylindrical; widest near midpoint; shape varying slightly from typical form in some species; surface punctate, punctures often obscured by scales; median sulcus present, sometimes not visible, beginning just beyond anterior constriction continuing to just anteriad of posterior margin. Anterior margin ranging from straight and even to slightly curved and somewhat produced dorsally, lateral margins evenly curved and widening into a bulge near midpoint, anteriorly constricted (sometimes subtly so); posterior margin straight to incurved. Pronotum in lateral view sub-cylindrical, narrower ventrally, with transverse ventrolateral sulci running sub-parallel to anterior and posterior margins, respectively; sometimes with scales forming a whitish stripe that continues along each elytron; with evenly spaced, anteriorly directed, sub-recumbent setae variously inserted near anterior margin; antero- and posterolateral margins with a fringe of appressed scales, with plumose setae beneath. Anterolateral margin with a full or reduced tuft of post-ocular vibrissae present, emerging near eye; vibrissae achieving a maximum length up to anterior-posterior length of eye.

Scutellum. Usually exposed, covered with appressed scales, triangular, equilateral, lateral margins slightly incurved.

Pleurites. Mesepisternum sub-triangular; mesepimeron trapezoidal, longer anterior edge meeting posterior side of mesepisternum; metepisternum linear, anteriorly abruptly widening into a triangular shape, gradually thinning posteriorly and covered by elytron near posterior portion of metasternum; metepimeron entirely covered by elytron.

Sterna. Prosternum longer than mesosternum; procoxal cavities positioned at midpoint, appearing contiguous, prosternal process usually not complete between coxae, slightly elevated. Mesosternum shorter than metasternum; anterior 1/2 incompletely covered by plumose scales, posterior portion as remainder of body surface; mesocoxal cavities separated by distance 1/6 –2/5× width of mesocoxal cavity. Metasternum with a more or less obscure transverse sulcus posteriad of anterior that continues to lateral extent of coxae; metacoxal cavities separated by 1.5 × their width. Metendosternite strongly reduced.

Legs. Prothoracic legs longer than mesothoracic legs; scale colors variously interspersed, setation generally similar to that of remainder of body surface; tibiae ventrally with rows of longer sub-erect setae, tibiae and trochanters of all legs with a single, hair-like, brown seta positioned on mesal surface, approximately 3 × length of adjacent setae. Profemur/pronotum length ratio 0.08-1.15; profemur moderately stout, slightly incurved, in cross section elliptical; proximal 4/5 of profemur gradually widening, then abruptly constricted with distal 1/5 produced ventrally as an obliquely rounded to semicircular projection covering tibial joint; condyle of tibial articulation occupying 4/5 of distal surface and 1/5 length of femur. Protibia/profemur length ratio 0.81-1.01; protibia typically moderately long and slender, straight, in cross section elliptical, apically expanded; protibial apex obliquely truncate, ventral setal comb situated on a flat surface, setal comb broken posteriorly, and becoming thinner and sparser anteriorly, setae also becoming shorter and more stout anteriorly; mucro present as a laterally projected tooth of variable size, triangular. Protarsus with tarsomere I nearly 2 × as long as II, elongate-conical; II and III similar in length, III wider than II; II conical, III bifid, jointly similar in length to V; IV mostly hidden by III; claw paired, separate, simple. Meso- and metathoracic legs slightly shorter and longer than prothoracic legs, respectively, all legs generally sub-equal in length with differences relatively small; mesotibiae with a pecten surrounding condylar surface, ring posteriorly interrupted; metatibial apex entirely scale covered, with strong outer bevel and inner flange ("corbel closed"; see Thompson 1992), outer bevel longer than inner flange, terminating in an oblique, almond-shaped convex ity ringed by a number of short, spiniform setae. Meso- and metatarsi similar to protarsi. All tarsi ventrally with spiniform setae.

Elytra. Length/width ratio 2.58-3.54; widest at anterior 1/5-2/5; anterior margins jointly 3/4-2 × wider than posterior margin of pronotum, curved posteriorly; humeri broadly rounded, not strongly projected; lateral margins slightly converging posteriorly, becoming more strongly rounded and converging apically; posterior margins constricted and narrower ventrally, posteriorly narrowly truncated. Elytra in lateral view convex, widening slightly posteriorly; posterior declivity broadly arcuate dorsally, nearly straight thereafter, angled at 45-80° to main body axis. Elytra with 10 complete striae; striae distinctly punctate, covered with scales, sub-equal in width to intervals; stria 10 and lateral margin sinuate; strial punctures distinct, variably separated by several times their diameter; intervals elevated and impunctate; scales completely covering integument, colors variously interspersed, most species have some specimens with a white stripe laterally continuing from pronotum, these stripes more or less defined on some specimens; each interval medially with a row of sub-erect to sub-recumbent setae.

Wings. Apterous.

Abdomen.Sterna. Ventrites III and IV jointed, V-VII free; scales similar to elytra, though generally of a lighter color, including rows of sub-erect setae; III longer than IV, midregion planar, posterior margin somewhat emarginate mesally, elevated and set off from IV along lateral 1/4-1/3s of its length, somewhat concave anteriorly; IV medially longer than V and VI jointly, laterally sub-equal in length; V and VI similar in length, margins straight. Sternum VII mesally 1/2-1 × as long as wide, sub-triangular; setae lengthening slightly and becoming darker and more erect posteriorly; anterior margin straight to broadly curved; posterior margin broadly arcuate, emarginate, and rimmed with short, posteriorly directed setae.

Terga. Tergum VII broadly arcuate posteriorly, somewhat convex, with interspersed setae becoming stouter and more densely arranged medio-posteriorally, posterior margin plicate and emarginate medially. Pygidium (tergum VIII) entirely covered by elytra, convex, sub-cylindrical to sub-conical (with lateral edges folded beneath), anterior edge broadly incurved mesally, posterior margin plicate, with a few minute setae inserted along rim; medial 1/3 of anterior 1/2 of pygidium less sclerotized.

Terminalia (Fig. 14). Sternum VIII. Anterior 7/8 (spiculum ventrale) narrowly stylate, anterior end slightly knobbed; posterior 1/8 (lamina) sub-quadrate, dorsally evenly concave, arms entire; anterior edges each incurved forming a slightly obtuse angle with lateral margin, produced to a point anteromedially at connection to spiculum ventrale; a less sclerotized region present anteriorly with anterior and lateral edges straight, latter sub-parallel; sclerotized region with pores laterally, more or less sclerotized medially; posterior edge plicate, with a fringe of sparse long setae.

Ovipositor. Coxites (distal gonocoxites) less sclerotized posteriorly, becoming more sclerotized anteriorly, 1/2 –2× as broad as long in dorsal view, slightly narrower posteriorly, and with sparse long setae throughout; styli sub-equal in length to coxites (latter short), digitate, narrowed apically, attachment to each coxite somewhat oblique, with 2 long setae near base. Genital chamber slightly shorter than sternum VIII.

Spermatheca. Comma-shaped; collum short, apically with a large, hood-shaped projection perpendicular to ramus, length and alignment with curvature of bulb of ramus variable, some species ante-apically with a long, perpendicular, cylindrical projection; collum short, cylindrical, sub-contiguous with, and typically angled at 90° to ramus; ramus elongate, bulbous, sometimes stalked, generally equal in thickness to corpus; corpus swollen or not; cornu elongate, apically, gradually narrowed, strongly recurved along its length.

Description - male.

Males are generally similar to females in appearance, and in many species are difficult to separate from female specimens. Variation within males can often exceed intersexual boundaries, further complicating their identification as male specimens. The description of males is therefore limited to characters and states that are sufficiently and consistently different between the sexes.

Habitus. Length 2.41-5.82 mm, width 0.90-2.72 mm, length/width ratio 1.77-3.17. Rostrum length 0.38-0.78 mm, rostrum/pronotum length ratio 0.42-0.81, rostrum length/width ratio 0.71-1.55. Pronotum length/width ratio 0.72-1.06. Profemur/pronotum length ratio 0.76-1.33, protibia/profemur length ratio 0.76-1.00. Elytra length/width ratio 2.72-3.59.

Mouthparts. As in female, mentum slightly more angular, broader, and produced laterally, overall with slightly straighter margins.

Elytra. Generally narrower relative to pronotum, elytral declivity slightly more angulate with regard to main body axis, but otherwise as in female.

Abdomen. Sternum IV relatively shorter, mesally slightly longer and laterally shorter than V and VI jointly. Sternum VII narrower than female, sub-trapezoidal, posterior margin straight mesally. Tergum VII convex, anterior margin posteriorly incurved, medially less sclerotized anteriorly, with interspersed setae becoming stouter and more densely arranged posteriorally, posterior margin cultellate and incurved mesally. Pygidium (tergum VIII) entirely covered by elytra, convex, sub-cylindrical (with lateral edges folded beneath), anterior margin broadly incurved, posterior margin arcuate, subtly incurved mesally, plicate; posteriorly punctate, each puncture with a single seta; anteriorly rugose.

Terminalia (Fig. 15). Sternum VIII. Consisting of 2 sub-triangular sclerites; each sclerite slightly wider anteriorly than long, with lateral and mesal margins curved, mesal margins with 6-8 setae posteriorly, anterior margins sinuate, laterally produced to a point; dorsal surface with a patch of short, fine setae laterally; spiculum relictum not apparent.

Spiculum gastrale (sternite IX) slightly longer than pedon of aedeagus; apical 1/5 expanded to an alate lamina (basal plate) with 2 sclerotized, gradually narrowing projections whose lateral margins are parallel. These projections located on lateral 1/3 of posterior margin, as long as sub-quadrate portion of lamina. Mesal 1/3 with a short, sub-trapezoidal projection. Stylus (apodeme of sternite IX) straight along mesal 1/2, curving gently along anterior 1/4; anteriorly explanate.

Tegmen. Slightly longer than pedon; tegminal apodeme (manubrium) stylate, feebly sinuate, and slightly expanded anteriorly; posterior ring with 2 posteriorly directed, narrowly triangular projections (parameres).

Aedeagus. Pedon length/width ratio 2.83-7.82; antero-ventral margin membranous, mesally curved; lateral margins gradually, evenly converging posteriorly to an acute point; in lateral view evenly curved; width becoming gradually narrower posteriorly, ventral margins in region of ostium sinuate; dorsally with sparsely arranged, short, fine setae laterally, becoming slightly more densely arranged meso-posteriorly; apex angulate. Ostium elongate-ovate, laterally emarginate, basal and apical edges each with a recurved invagination. Internal sac variously plicate, membranous except for 2 sclerotized, sinuate-uncinate rami; gonopore projecting as a flagellum, anteriorly extending along aedeagal apodemes, with an apical sclerite, sclerite highly variable in form within the genus. Aedeagal apodemes (temones) slightly longer than pedon, each posteriorly embedded in a lateral fold of pedon, sclerotized throughout, becoming wider and less sclerotized anteriorly.

Distribution.

Members of Minyomerus [JF2015] are distributed across the desert and grassland regions of North America (Figs 50-52). They are found as far north as Alberta, Canada, and south to Baja California Sur and San Luis Potosí, Mexico. Their range extends from the western Mojave Desert to Missouri.

Natural history.

Minyomerus [JF2015] species have a range of host plants with which they can be associated; they are commonly found on creosote bush ( Larrea tridentata (DC.) Coville [non-focal; Zygophyllaceae [non-focal]), broomweed ( Gutierrezia Lagasca [non-focal; Asteraceae [non-focal), sagebrush ( Artemisia Linnaeus [non-focal]; Asteraceae [non-focal]), and occasionally on other various Asteraceae [non-focal]. It is likely that the larvae are root feeders, as are other tanymecine [non-focal] weevils, but this has not been directly observed. Adults are found on the stems and leaves of their host plant during day and night. Some species of Minyomerus [JF2015] are active during the hottest parts of the day; others might possibly take shelter near the roots of the host. Many species have overlapping distributions and can occur sympatrically in certain areas, and in many cases on the same individual plants. They can be collected by beating, sweeping plants, light trapping, and with pitfall traps.