Minyomerus laticeps [JF2015] (Casey, 1888) 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 : 23-25

Taxon classification Animalia Coleoptera Curculionidae

Minyomerus laticeps [JF2015] (Casey, 1888) sec. Jansen & Franz (2015) Figs 9, 10, 11

== AND = Elissa laticeps Casey, 1888: 272 sec. Casey (1888)

Diagnosis.

Minyomerus laticeps [JF2015] is most easily distinguished from other congenerics by the unique shape of the head, which is very wide and only somewhat swollen between the eyes. The rostrum is also much wider than long, and the nasal plate is weakly impressed. Additionally, the anterior margin of the prothorax is larger than the posterior margin and bears a well-developed tuft of post-ocular vibrissae. The spermatheca is unique in having the ramus stalked, with the apical bulb abruptly constricted, not tapering, at the point of connection with the stalk. The small, sub-recumbent setae and lack of separation of the procoxae help to distinguish this species from Minyomerus griseus [JF2015] and Minyomerus rutellirostris [JF2015].

Redescription - female.

Habitus. Length 3.90-5.74 mm, width 1.51-2.22 mm, length/width ratio 2.37-2.63, widest at anterior 1/4 of elytra. Integument tan, orange-brown to dark brown. Scales with variously interspersed colors ranging from slightly off-white to manila/tan to dark coffee brown, in some specimens appearing semi-translucent (in others opaque). Setae sparse throughout, short, sub-recumbent.

Mandibles. Covered with opalescent scales, with 4 longer setae, and a number of shorter interspersed setae.

Maxillae. Cardo bifurcate at base with an inner angle of ca. 90°, arms of equal length, inner (mesal) arm 1.5 × thicker than outer arm, both arms of bifurcation equal in length to apically outcurved arm. Stipes sub-quadrate, slightly longer than wide, roughly equal in length to each bifurcation of cardo, glabrous. Galeo-lacinial complex mesally membranous, laterally sclerotized, with sharp demarcation of sclerotized region separating palpiger from galeo-lacinial complex; setose in membranous area just adjacent to sclerotized region, setae covering half of dorsal surface area; dorsally with 8 apicomesal lacinial teeth; ventrally with 5 reduced lacinial teeth. Palpiger with a row of setae extending laterally along basal 1/2, thereafter becoming abruptly transverse; anterior 1/2 membranous.

Maxillary palps. I and II both apically oblique, apical ends forming a 45° angle with base, I and II each with 2 apical setae; II with 1 mesoventral seta in addition to 2 apical setae.

Labium. Prementum roughly hexagonal; apical margin laterally incurved, angulate. Labial palps 3-segmented, II with apical 1/3 projecting beyond margin of prementum, but not reaching apex of ligula; III slightly longer than II.

Rostrum. Length 0.52-0.73 mm, anterior portion 3-4 × broader than long, rostrum/pronotum length ratio 0.53-0.61, rostrum length/width ratio 0.73-0.89; shape in cross section elongate-rectangular. Dorsal outline of rostrum sub-rectangular, posterior half of dorsal surface strongly rugose. Rostrum in lateral view nearly square; apical margin with 2 large vibrissae. Nasal plate weakly defined by V-shaped, impressed lines, slightly convex, with opalescent scales. Margins of mandibular incision directed 15° outward dorsally in frontal view; ventrolateral sulci usually weakly defined or obscure, if strongly defined then only as a notch dorsad of insertion point of mandibles. Dorsal surface of rostrum transversely impressed (strongly or weakly in some specimens), with median sulcus running from fovea at posterior end of rostrum to imaginary transverse line between anterior margins of eyes. Oral cavity with lateral margins feebly curved.

Antennae. Scrobe continuing to anterior 1/2 of eye; small tooth formed by overhanging dorsal margin of scrobe ventrad of anterior 1/3 of eye. Scape nearly extending to posterior margin of eye. Terminal funicular antennomere lacking appressed scales, having instead a covering of apically-directed pubescence with interspersed sub-erect setae. Club nearly 3 × as long as wide, with setation and pubescence as in final segment of funicle.

Head. Eyes with posterior margin slightly elevated from lateral surface of head; eyes separated in dorsal view by 4 × their anterior-posterior length, set off from anterior prothoracic margin by 1/3 of their anterior-posterior length. Head between eyes rugose and slightly bulging, appearing flat in some specimens. Head without any transverse post-ocular impression.

Pronotum. Length/width ratio 0.75-0.89, sub-cylindrical to slightly globular; widest after midpoint before anterior constriction. Anterior margin nearly straight, subtly incurving mesally, lateral margins feebly curved, posterior margin incurved. Pronotum in lateral view with setae that barely reach beyond anterior margin. Anterolateral margin with a tuft of post-ocular vibrissae present, emerging near dorsal margin of eye, becoming gradually, evenly longer ventrally, stopping just above ventral margin of eye; vibrissae achieving a maximum length nearly as long as anterior-posterior length of eye.

Pleurites. Metepisternum covered by elytron near posterior 1/4 of metasternum.

Thoracic sterna. Mesocoxal cavities separated by distance 1/3-2/5 × width of mesocoxal cavity. Metasternum with transverse sulcus usually apparent (faint in some specimens); metacoxal cavities widely separated by 3-4 × their width.

Legs. Profemur/pronotum length ratio 0.96-1.09; distal 1/5 of profemur produced ventrally as a semicircular projection covering tibial joint. Protibia/profemur length ratio 0.88-0.91; protibia with ventral setal comb recessed in a broadly concave groove, setal comb unbroken, but becoming thinner and sparser anteriorly; mucro reduced to a very small laterally projected tooth. Protarsus with tarsomeres II and III similar in length, equilateral. Metatibial apex with almond shaped convex ity ringed by 8 short, widely separated, spiniform setae.

Elytra. Length/width ratio 2.74-2.95; widest at anterior 1/4; anterior margins jointly 1.25-1.50 × wider than posterior margin of pronotum; lateral margins sub-parallel after anterior 1/4, more strongly rounded and converging in posterior 1/2. Posterior declivity angled at nearly 70° to main body axis. Elytra with striae shallow, punctate, punctures faint beneath appressed scales, separated by 3-4 × their diameter; intervals very slightly elevated.

Abdominal sterna. Ventrite III elevated and set off from IV along lateral 1/4s of its length, anteriorly planar. Sternum VII mesally 3/5-2/3 × as long as wide; setae darkening, lengthening, and becoming more erect in posterior 1/4; anterior margin weakly curved.

Tergum. Pygidium sub-cylindrical; medial 1/5 of anterior 2/3 of pygidium less sclerotized, with a patch of very short, fine setae.

Sternum VIII. Anterior laminar edges of spiculum ventrale each incurved forming a 110° angle with lateral margin; lamina more sclerotized medially. Ovipositor. Coxites nearly as broad as long.

Spermatheca.?-shaped; collum short, apically with a large, hood-shaped projection sub-parallel to ramus, nearly equal in length and contiously aligned with curvature of bulb of ramus; collum sub-contiguous with, and angled at 45°-60° to ramus; ramus basally elongate, forming a stalk (length variable among examined specimens), bulbous apically, 4 × thicker than stalk; corpus not swollen, of equal thickness to collum and cornu; cornu elongate, apically, gradually narrowed, strongly recurved in basal 1/4, straight along mesal 1/2, and curved near apical 1/4 such that apex is parallel to collum and corpus.

Male.

Similar to female, except where noted. Length 3.50-4.67 mm, width 1.26-1.70 mm, length/width ratio 1.77-1.96. Rostrum length 0.60-0.77 mm, rostrum/pronotum length ratio 0.53-0.61, rostrum length/width ratio 0.73-0.89. Pronotum length/width ratio 0.75-0.82. Profemur/pronotum length ratio 1.17-1.25, protibia/profemur length ratio 0.85-0.96. Elytra length/width ratio 2.88-3.10.

Elytra. Generally shorter and narrower relative to pronotum, but otherwise as female.

Abdomen. Sternum VII slightly more broadly arcuate posteriorly, 1/2 -3/5 as long as wide. Pygidium (tergum VIII) with mesal 1/3 of posterior margin nearly straight; posterior 1/2 punctate; anterior 1/2 rugose.

Aedeagus. Length/width ratio 4.25-4.71; lateral margins very slightly converging posteriorly, diverging in region of ostium, then converging into a large, spadiform projection that is roughly the size of the ostium. In lateral view, width of pedon becoming gradually narrower posteriorly in anterior 2/3, ventral margins in posterior 1/3 becoming straight towards apex; apex acutely angulate. Flagellum apically with a small, sub-cylindrical sclerite, sclerite posteriorly with two small, lateral flanges.

Comments.

Specimens can vary somewhat in color, from dark brown to beige. Some specimens exhibit a relatively narrower prothorax, depending on the locality. The bulging of the head and form of the rostrum can also vary slightly, with some specimens exhibiting a smaller rostrum and more bulbous head.

Material examined.

Holotype - female "●Tex [Casey locality code: El Paso including both banks of the River Grande which is here about 100 ft. in width]/ Casey bequest 1925/ Type USNM 35005 [red]/ Elissa laticeps Cas" (USNM). Syntypes - "Ari● [Casey locality code: Benson (Collected by G.W. Dunn)]/ Type USNM? Syntype [red]/ Elissa laticeps 10785 Casey" (USNM: 1 female); "Ari●/ Casey bequest 1925/ Casey determ. laticeps-2 [part of series, ranging 2-6]/ Type USNM Syntype? [red]" (USNM: 5 females). Additional specimens examined: "Cochise Co., Ariz, T17S-R31-E-3--, 27 VIII 59, 092/ Minyomerus laticeps , det. D.G. Kissinger" (CSCA: 3 females); "N. Mex. 17 mi. NE. Las Cruces, Jornada Expt. Rge. X-3-1970/ Larrea tridentata [non-focal] at night, C.W. O’Brien / Compared with type Elissa laticeps Csy 1977 [green]" (CWOB: 8 females); "TEX. Big Bend N.P. Grapevine Hills Ranch, III-27-1970/ on mesquite, C.W. O’Brien” (CWOB: 1 female); "TEX. 57 mi. S. Alpine, Brewster Co. 6-6-1970/ Collectors: L&C.W. O’Brien” (CWOB: 1 female); "AZ, Pima Co. 1 mi. N. Hwy 86, 2 mi. S, San Pedro, Sept. 8 2008 CW. O’Brien / on Larrea tridentata [non-focal]" (CWOB: 4 females); "Ariz.: Coch. Co., 5 mi N Portal, IX-21-1976, DS Chandler" (CWOB: 1 female); "MEX., Coah. 23 mi. W. Saltillo 4200', night 8-20-1971, O’Briens & Marshall" (CWOB: 59 females) [15 females deposited at CMNC]; "MEX., Coah. 4 mi. W. Saltillo 5600', night 8-20-1971, O’Briens & Marshall" (CWOB: 3 females); "MEX., Coah. 13 mi. W. Saltillo night, 4850' 8-20-1971, O’Briens & Marshall" (CWOB: 3 females); "MEX. 14 mi. W. Monterrey, x-18-1970, C.W. O’Brien” (CWOB: 5 females); "Presidio Tex, X-28-44, JHRussel/ on Larrea divaricata [non-focal], foliage, 44-26374" (USNM: 10 males, 10 females).

Distribution.

This species has been found in the desert and arid regions of Arizona, New Mexico, Texas (USA), Nuevo Leon, Coahuila, and Baja California Sur (Mexico). It is likely that its range also includes southern California (USA), Baja California, northern Chihuahua, and Sonora (Mexico), based on similarity in habitat to the currently known distribution (Fig. 50).

Natural history.

Associated with creosote bush ( Larrea tridentata [DC.] Coville [non-focal]; Zygophyllaceae [non-focal]) and mesquite ( Prosopis [non-focal] spp.; Fabaceae [non-focal]).