Megalocraerus chico, Caterino, Michael S. & Tishechkin, Alexey K., 2016

Caterino, Michael S. & Tishechkin, Alexey K., 2016, A revision of Megalocraerus Lewis, 1902 (Coleoptera, Histeridae: Exosternini), ZooKeys 557, pp. 59-78 : 70-71

Taxon classification Animalia Coleoptera Histeridae

Megalocraerus chico sp. n. Figs 5C, 6 C–D, 8

Type material.

Holotype male: "Rancho Quemado, Península de Osa, 200 m, Prov. Punt., COSTA RICA. F.Quesada, Dic 1991, L-S 292500, 511000" / "INBIO CRI000331213" (INBIO); Paratype female: Turrialba, CATIE [Centro Agronómico Tropical de Investigacion y Enseñanza], 22.vi.-5.vii.1984, H.L.Dozier (FSCA).

Diagnosis.

This species is relatively small and dorsoventrally depressed. It is similar overall to Megalocraerus mandibularis , but lacks the modified male mandibles of that species. They also differ in tarsal setae, which are flattened and sublaminate in this species, but simple in Megalocraerus mandibularis . An additional form that we do not describe from French Guiana keys out with this species, although that entity is significantly larger and has more conspicuous meso- and metaventral punctation. This species and Megalocraerus madrededios both have the 4th dorsal stria connected to the sutural arch, but the latter species is more distinctly broad and flattened, as well as lighter in color. Finally, the distinct medioventral process of the aedeagus is unique.

Description.

Size: Length 2.9-3.0 mm; width 2.0 mm; Body: broad, subparallel-sided, elongate, moderately depressed; piceous to weakly castaneous. Head: Frons finely and doubly punctate, with medium punctures separated by slightly more than their diameters against fine ground punctation, decreasing in size but slightly increasing in density anteromediad; frontal stria present along inner margins of eyes, bent inward above antennal insertions, broadly interrupted across epistoma; supraorbital stria absent; epistoma depressed, narrowing anterad; labrum minutely punctate; mandibles each with inner marginal tooth. Pronotum: Pronotal sides straight, subparallel in basal three-fourths, abruptly narrowed anteriorly, marginal stria complete, lateral stria absent, anterior marginal stria more or less complete; pronotal disk with numerous shallow, elongate secondary punctures at sides and front, diminishing basomedially, with fine ground punctation largely restricted to basal area; basal margin with coarser punctures. Elytra: Two complete epipleural striae present; subhumeral striae absent; dorsal striae 1-4 complete, 1-3 variously continued mediad along basal margin, 4th meeting basal arch of sutural stria, 5th stria obsolete in anterior fourth; elytral disks with conspicuous ground punctation throughout, coarser secondary punctures present in apical sixth. Prosternum: Prosternal lobe evenly, somewhat narrowly rounded, complete to sides, marginal stria obsolete at sides; prosternal keel with two complete carinal striae diverging slightly front and rear, continued around basal projection of keel (may be fragmented). Mesoventrite: Anterior mesosternal margin evenly emarginate, with complete marginal stria; mesometasternal ventral absent; disk with only fine ground punctation. Metaventrite: Metaventral disk impunctate at middle, lateral metaventral stria present, extending toward outer corner of metacoxa, slightly abbreviated apically; postmesocoxal stria very short. Abdomen: Abdominal ventrites finely punctate at middle, slightly more coarsely at sides; propygidium strongly transverse, about four times as wide as long, coarsely punctate, with punctures separated by slightly less than their diameters, rather uniformly throughout; pygidium similarly coarsely punctate at base, punctures becoming finer, but also denser toward apex. Male: 8th tergite with deep but rather broad basal emargination, ventrobasal processes thin, distant beneath, dorsally with fine, deep median emargination, with desclerotized line extending nearly to base; halves of 8th sternite slightly separated along midline, apicomedial processes rather narrow, subacute; 9th tergite with blunt, incurved apices; spiculum gastrale (S9) broad in basal third, abruptly narrowed, thence broadening to head, apex shallowly emarginate; 10th tergite entire; aedeagus flattened throughout, with distinct medioventral process, sides weakly rounded, widest near midpoint, apices slightly separated; median lobe slightly less than one-half tegmen length.

Remarks.

The name of this species (Spanish for ‘small’) refers to its relatively small size. In this case it is used as a noun in apposition. This species was included in the phylogenetic analysis of Caterino and Tishechkin (2015) as ' Megalocraerus 2'.