Pectinosoma Arrow, 1913

Katovich, Kerry, 2008, A generic-level phylogenetic review of the Macrodactylini (Coleoptera: Scarabaeidae: Melolonthinae), Insecta Mundi 2008 (23), pp. 1-78 : 56-57

Pectinosoma Arrow, 1913

( Figure 141-145 )

Pectinosoma Arrow, 1913: 430 . Type species Pectinosoma elongatum Arrow, 1913 , by monotypy.

Taxonomic Notes

The following generic diagnosis is based on a single dissected male syntype of the type species, P.

elongatum (BMNH) .

Generic diagnosis

This genus is characterized by its elongate body, large size, distinct coloration pattern; prementum elongate, ventral surface with a medial groove; mesosternum trapezoidal, flattened, anteriorly obscured by an elevated process; 5 th ventrite raised medially, posteriorly raised into a prominent process; pretarsus with all claws simple. The type species name was changed to P. elongata and is here changed back to the original gender-neutral P. elongatum .

Generic redescription

Measurements: Prothorax at widest point 5.0 mm, elytra at widest point 4.8 mm, length 18.0 mm.

Color and vestiture: Head and pronotum black, abdomen and elytra black, legs reddish brown, margins of elytra and pronotum lined with white setae.

Head: Clypeus not coplanar with frons; frons angled at 30 o; labrum in frontal view narrow, rectangular, emarginate, labrum not coplanar with clypeus; labium with prementum elongate, ventral surface with a medial groove ( Fig. 143 ); mandibles in dorsal view semicircular, scissorial area very narrow, blunt, directed aborally, thin in lateral profile, well sclerotized, molar area produced aborally, well sclerotized; maxillary palpi with apical palpus ovate, equal to segments 2-3; antennae with 9 antennomeres, antennomeres 7-9 forming the club, equal in length to antennomeres 3-6 combined.

Prothorax: Pronotum oblong, longer than wide, widest at 2/3 distance form anterior, anterior angle acute, appearing toothed, lateral margin convex, margin with a slight bread, in posterior 1/3, posterior angle obtuse, posterior margin weakly convex, margin with a slight bead; prothoracic leg with coxa transverse; tibia dentate; pretarsus with claws not divergent, equal in length, both claws simple, base of claw toothed.

Mesothorax: Mesosternum trapezoidal, flattened, anteriorly obscured by bifurcate prosternal process, posterior margin convex ( Fig. 144 ); scutellum subtriangular; elytra longer than wide, widest in anterior 1/4, epipleuron with slight deflexed margin, slight membrane along margin, elytral surface lacking clear striae, anterior umbones prominent, posterior umbone very weakly developed; pretarsus similar to prothoracic pretarsus.

Metathorax: Metathoracic leg with coxa widely separated; femur ovate, widest in distal 1/4; tibia clavate, narrow proximally; posteroventral margin with pair of spurs, ventral spur short, broad, dorsal spur elongate, narrow, spurs raised above level of tarsal articulation joint, posterior margin with several elongate setae, margin with a deep, U-shaped groove; pretarsus with claws and empodium similar to prothoracic and mesothoracic claws.

Abdomen: First ventrite strongly angled dorsally, 2 nd ventrite equal to length of 1 st ventrite, ventrites 3-4 subequal in length, hollowed out medially, 5 th ventrite (= propygidium) subequal in length to ventrites 3-4 combined, raised medially in anterior, posteriorly raised into a prominent trapezoidal process, process with distal margin lined with cylindrical elements, lateral margins of process grooved ( Fig. 145 ), ventrite and sternite of 5 th abdominal segment not separated by a suture, spiracle placed anteriorly, 6 th ventrite equal to length of 4 th ventrite, flattened; pygidium longer than wide.

Diversity and Geographic Distribution

Pectinosoma is monotypic, with P. elongatum known only from Guyana.

Figures

Figure 141-145. Pectinosoma elongatum Arrow (male). 141) Dorsal habitus. 142) Left lateral view.143) Prementum, ligula and labial palpi, ventral view. 144) Mesosternum, ventral view. 145) Visible abdominal segments.