Ancistrosoma Curtis, 1835

Katovich, Kerry, 2008, A generic-level phylogenetic review of the Macrodactylini (Coleoptera: Scarabaeidae: Melolonthinae), Insecta Mundi 2008 (23), pp. 1-78 : 18-19

Ancistrosoma Curtis, 1835

( Figure 12-16 )

Ancistrosoma Curtis, 1835: 307 . Type species Ancistrosoma klugi Curtis, 1835 , by monotypy.

Taxonomic Notes

The diagnosis is based on a dissected homeotype of A. trinitatis Arrow (IRC) . Specimens were compared with the type species located at the BMNH. The type species, A. klugi Curtis , was not located at the BMNH. Specimens of A. klugi were located at several collections and a comparison of generic characters was made with A. trinitatis .

Generic diagnosis

The genus is characterized by its large size, elongate body, pronotum with the posterior margin bearing a single, narrow acuminate medial process; mesosternum medially interrupted by a broad triangular extension of the prosternum; 1st abdominal ventrite with posterior margin bearing a narrow, blunt acuminate process medially in males.

Generic redescription

Measurements: Prothorax at widest point 6.2 mm, elytral at widest point 9.6 mm, elytral length 20.0

mm.

Color and vestiture: Body brown, surface glabrous, vestiture consisting of yellowish setae.

Head: Clypeus not coplanar with frons; frons angled at 30 o; labrum in frontal view narrowly ovate, weakly emarginate, labrum not coplanar with clypeus; labium with prementum quadrate, ventral surface medially grooved ( Fig. 14 ); mandibles rectangular, scissorial area bluntly produced, narrow, concave, molar area bluntly produced adorally; maxillary palpi with apical palpus ovate, apex acute; antennae with 9 antennomeres, antennomeres 7-9 forming the elongate club, equal in length to antennomeres 2-6 combined.

Prothorax: Pronotum oblong, transverse, width subequal to length, widest medially, anterior angle acute, appearing toothed, lateral margin convex, posterior angle acute, appearing toothed, posterior margin weakly concave, medially with a narrow acuminate process, dorsal surface rounded ( Fig. 15 ); prothoracic leg with coxa elongate; tibia bidentate; pretarsus with claws divergent, equal in length, both claws broadly split, upper lobe narrow, slightly longer than narrow, lower lobe of individual claw.

Mesothorax: Scutellum subtriangular, anterior margin convex, medially with a deep emargination; elytra longer than wide, widest in anterior 1/4, elytral epipleuron flattened, membranous, dorsal surface with three weakly raised striae, interstrial regions setose, anterior and posterior umbones strongly produced; pretarsus similar to prothoracic pretarsus.

Metathorax: Coxae widely separated; femur ovate, width subequal along entire length; tibia subtriangular, narrow proximally, widest distally, posteroventral margin with a pair of elongate spurs, anterior spur short, spurs arise from same plane as tarsal segment articulation joint, posterior margin with a shallow, U-shaped groove; pretarsus with claw articulation grooves present; claws similar to prothoracic claws.

Abdomen: First ventrite equal in length to ventrites 2-4, posterior margin medially with a narrow, blunt acuminate process, process extends approximately to posterior margin of 3 rd ventrite ( Fig. 16 ), 2 nd ventrite length equal to length of ventrites 3-4 combined, partially obscured by 1 st ventrite, ventrites 3-4 equal in length, 5 th ventrite (= propygidium) equal to 1.5X length of 4 th ventrites, ventrite and sternite of 5 th abdominal segment of propygidium not separated by a suture, spiracle placed in anterior 1/4, 6 th ventrite equal in length to 5 th ventrite, flattened, posterior margin straight, membranous; pygidium subtriangular, wider than long, posterior margin weakly concave.

Diversity and Geographic Distribution

Ancistrosoma comprises 15 species. Their distributions are centered in Colombia, Ecuador, Peru, Venezuela, Trinidad and Tobago, and a single species is recorded from Argentina. Keys to species are provided by Arrow (1913).

Figures

Figure 12-16. Ancistrosoma trinitatis Arrow (male). 12) Dorsal habitus. 13) Left lateral view. 14) Prementum, ligula and labial palpi, ventral view. 15) Pronotum, dorsal view. 16) Visible abdominal segments, ventral view.