Macrodactylus Dejean, 1821

Katovich, Kerry, 2008, A generic-level phylogenetic review of the Macrodactylini (Coleoptera: Scarabaeidae: Melolonthinae), Insecta Mundi 2008 (23), pp. 1-78 : 50-52

Macrodactylus Dejean, 1821

( Figure 120-124 )

Macrodactylus Dejean, 1821: 58 . Type species Melolontha subspinosa Fabricius, 1775 , by subsequent designation ( Evans 2003: 290).

Stenothorax Harris, 1827: 8 . Type species Stenothorax subspinosa (Fabricius), 1775 , by monotypy.

Taxonomic Notes

The following generic diagnosis is based on four dissected homeotypes of the presumptive syntype of the type species M. subspinosus located at the MNHC, and identified with a Fabricius label .

Generic diagnosis

This genus is characterized by its elongate body, often with a vestiture consisting of scale-like setae; prementum elongate, medially grooved; pronotum hexagonal, longer than wide, widest medially.

Generic redescription

Measurements: Prothorax at widest point 2.4 mm, elytra at widest point 3.7 mm, length 10.0 mm.

Color and vestiture: Head, thorax and abdomen dark brown; body with a vestiture consisting of short, broad, dense yellow recumbent setae.

Head: Clypeus coplanar with frons; frons angled at 30 o; labrum in frontal view, oval, narrow, weakly emarginate, labrum coplanar with clypeus; labium with prementum rectangular, elongate, ventral surface with medial groove ( Fig. 122 ); mandibles in dorsal view triangular, scissorial area reduced to a membrane, lined with dense setae, molar area well developed, weakly sclerotized; maxillary palpi with apical palpus oval, equal to length of segments 1-2 combined, apex with blunt sensory region; antennae with 9 antennomeres, antennomeres 7-9 forming the club, lamellae thin, elongate, equal to length of antennomeres 3-6 combined.

Prothorax: Pronotum hexagonal, transverse, widest medially, anterior angle obtuse, lateral margin convex medially, posterior angle obtuse, posterior margin weakly concave ( Fig. 123 ); prothoracic leg with coxa elongate; tibia dentate, with a small spur (absent in males) 1/4 distance from distal apex; pretarsus with claws divergent, equal in length, both claws narrowly split, outer lobe narrow, slightly longer than lower lobe, lower lobe broad on individual claw.

Mesothorax: Scutellum cordiform; elytra longer than wide, width uniform, elytral epipleuron narrowly flattened, membranous, dorsal surface with striae distinct, intervals slightly convex, surface covered with short, broad, yellow setae, anterior umbone strongly developed, posterior umbone very weakly developed; pretarsus similar to prothoracic pretarsus.

Metathorax: Metathoracic leg with coxae clearly separated; femur elongate, weakly ovate, widest medially; tibia triangular, broader distally; posteroventral margin with subequal spurs (absent in males), spurs arising from same plane as tarsal articulation joint, posterior margin lacking a U-shape groove; pretarsus with claws similar to prothoracic and mesothoracic legs and empodium.

Abdomen: Ventrites 2-4 subequal in length, 5 th visible ventrite (= propygidium) 1.5X length of ventrite 4 length, 5 th visible ventrite and sternite of 5 th abdominal segment with suture lacking, spiracle placed medially, 6 th ventrite triangular, posterior 1/2 membranous; pygidium triangular, posterior margin rounded, longer than wide in males ( Fig. 124 ).

Diversity and Geographic Distribution

Macrodactylus comprises 109 species, distributed from Argentina, Belize, Bolivia, Brazil, Canada, Chile, Colombia, Costa Rica, Ecuador, Guatemala, Mexico, Nicaragua, Panama, Paraguay, Peru, United

States, and Venezuela. Regional keys provided by Horn (1876), Carrillo and Gibson (1960), Morón (1994), and Arce-Pérez and Morón (2000).

Figures

Figure 120-124. Macrodactylus subspinosus (Fabricius) (female). 120) Dorsal habitus. 121) Left lateral view. 122) Prementum, ligula and labial palpi, ventral view. 123) Head, pronotum, scutellum, dorsal view. 124) Pygidium, dorsal view.