Diplotaxis riusi Delgado, 2011

Delgado, Leonardo, 2011, A New Species of the GenusDiplotaxisKirby, 1837 (Coleoptera: Scarabaeidae: Melolonthinae: Diplotaxini) from Northeastern Mexico, The Coleopterists Bulletin 65 (2), pp. 189-191 : 189-191

Diplotaxis riusi Delgado , new species ( Figs. 1–2 )

Type Material. Holotype male and five male paratypes labeled “ MÉXICO: Nuevo León, Santiago ,

Cola de Caballo, 28.iii.1979, J. Figueroa col.”. Two male paratypes labeled “ MÉXICO: Nuevo León, Santiago, Potrero Redondo, 28.iii.1979, H. Pérez col.”. The holotype and three paratypes are deposited in the entomological collection of the Instituto de Biología, UNAM (Mexico City). Four paratypes are deposited in the following collections: Instituto de Ecología , A. C. (Veracruz, Mexico), Scott McCleve collection ( Douglas , Arizona, USA), and L. Delgado collection ( Mexico City , Mexico ) .

Holotype. Male. Length 12.6 mm; maximum width across elytra 7.4 mm. Body oval, convex. Head, pronotum, venter, and legs shiny black; elytra dull black. Dorsum glabrous. Length of clypeus 2/5 cephalic length; apex of clypeus emarginate between rounded angles, sides oblique; margin moderately reflexed at middle, to sides less reflexed; canthus not prominent; surface of clypeus tumid at lateral third; clypeus densely rugose; reflexed underside of clypeus transversely furrowed. Frontoclypeal suture complete, straight at middle and curved at sides. Front of head transversely tumid behind clypeus, with a middle impression; surface of frons coarse and densely punctate, punctures becoming smaller and sparser to vertex. Transverse eye diameter almost 1/7 as wide as head. Antennae with 10 antennomeres. Labrum distinctly concave longitudinally, frontal margin strongly arcuate, labrum at middle almost 1.5X longer than and distinctly advanced from the reflexed underside of clypeus. Mandibles large, bulbous; last segment of maxillary palp with small, dorsal, basal impression. Mentum not sunken, concave with transverse declivity posteriorly bounded by a blunt and glabrous edge.

Pronotum much wider than long (1.00:0.53), sides moderately curved, widest slightly behind the middle, base with tiny denticulations at lateral third, anterior angles slightly acute and slightly concave, posterior angles obtuse and almost flat; surface of pronotum with moderately dense punctures of same size as those of frons, punctures sparser at middle. Scutellum with few basal punctures. Elytra longer than wide (1.00:0.74), flat, sparsely punctuate; striae and broad intervals with punctures larger than those of pronotum, costae with minute and scarcely visible punctures, sutural interval with scarce, minute punctures; margins with few small setae at basal third. Abdomen laterally rounded, second and third visible sternites with two small rounded swellings at middle; propygidium distinctly grooved; pygidium wider than long and slightly convex, surface with coarse, sparse, setiferous punctures.

Protibiae tridentate with the apical inner border cut-out, basal tooth situated in front of middle and separated from anterior two teeth; first mesotarsomere longer than second; metafemora scarcely punctate between the marginal rows of punctures; metacoxae laterally angled; tarsi longer than respective tibiae; claws gently curved, tooth nearer apex of claw than base, and slightly longer and wider than apex of claw. Genitalia with parameres shorter than basal piece, jointed on inner margin at about basal fourth, and with minute setae on apical and ventral surfaces ( Figs. 1–2 ).

Variation. Males (seven paratypes). Length 12.1–13.5 mm; maximum width across elytra 6.6–7.8 mm. In some specimens the swellings at the lateral third of the clypeus are more distinct, and the convexity of the front of the head is more pronounced. The angles of the pronotum may be more concave than in the holotype, and the punctation of head, pronotum, and elytra varies slightly in density.

Female. Unknown.

Etymology. It is my pleasure to name this species for Eduardo del Río García, known by the nickname Rius, who is a great Mexican cartoonist and social critic, and resident of the state of Morelos. His extensive work has been translated into several languages, and has been read by many generations.

Distribution. Diplotaxis riusi is known from two nearby localities about 40 km southeast of the city of Monterrey, Nuevo León, Mexico. These localities have a humid forest with oak ( Quercus L., Fagaceae ) as the principal tree element. They range in elevation from 750 m to 850 m. These features contrast with the drier forests inhabited by Diplotaxis belfragei Fall and Diplotaxis bakeri Cazier , the two species seemingly most closely related to D. riusi .

Remarks. Diplotaxis riusi belongs to the D. brevicollis-haydenii species-group because of the following characters: dorsum entirely glabrous; clypeus with anterior angles rounded; reflexed underside of clypeus transversely furrowed; mandibles large and bulbous; labrum prominent and situated in front of the underside of clypeus; eyes small, not reaching the gular region; antennae with 10 antennomeres; protibiae tridentate with the apical inner border cut-out; first mesotarsomere longer than second; and metacoxae laterally angled. Within this species-group, D. riusi shares the following characters with D. belfragei and D. bakeri : length of clypeus less than one-half the cephalic length; apical margin of clypeus distinctly emarginated; base of clypeus without transverse ridge extending almost from eye to eye, labrum deeply concave with its frontal margin strongly arcuate; labrum no more than twice wider than long, at middle distinctly longer than reflexed underside of clypeus; mentum concave with transverse declivity posteriorly bounded by a distinct and glabrous edge; pronotum with front and hind angles feebly concave; and hind femora scarcely punctate between the marginal rows of punctures.

Diplotaxis riusi differs from D. bakeri in having the body length equal to or greater than 12 mm (equal to or less than 11 mm for D. bakeri ) and the front of head transversely tumid (flat in D. bakeri ). From D. belfragei , the new species differs by the head having punctures smaller and sparser (coarse and densely punctate in D. belfragei ). From both species, D. riusi differs by the clypeus being tumid at lateral thirds (entirely flat in D. bakeri and D. belfragei ), the dull elytra (not shiny in D. bakeri and D. belfragei ), the elytral costae with minute, scarcely visible punctures (with small, distinct punctures in D. bakeri and D. belfragei ), and parameres shorter than basal piece and with minute setae on apical and ventral surfaces ( Figs. 1–2 ) (parameres as long as the basal piece and glabrous in D. bakeri and D. belfragei ).

The key to the D. brevicollis-haydenii speciesgroup given by Vaurie (1960) is modified as follows to incorporate D. riusi :

20. Clypeus feebly emarginate in front and as long as at least one-half length of head; declivity of mentum appearing rather flat, not advanced; Arizona and northwestern Mexico................................ D. boops in part

20′. Clypeus distinctly emarginate and about one-third length of head; declivity of mentum either advanced prominently as a ledge or deeply concave from side to side............ 20a

20a. Clypeus tumid at lateral third; elytra opaque; parameres with minute setae on apical and ventral surfaces; northeastern Mexico.......... .................................... D. riusi , new species

20a′. Clypeus entirely flat; elytra shiny; parameres glabrous.....................................................21

21. Head coarsely punctate; declivity of mentum usually as long as one-half length of mentum; length 10–14 mm; claws toothed either medially or subapically; western United States and northeastern Mexico.................. D. belfragei

21′. Head finely, shallowly punctate; declivity of mentum usually no longer than one-third length of mentum; length 8.5–11.0 mm; claws toothed in front of middle; northeastern Mexico........................................... D. bakeri

Figures

Figs. 1–2. Parameres of Diplotaxis riusi. 1) Caudal view; 2) Lateral view.