Ligyrodes Casey 1915
Creators: name: López-García, Margarita M.
name: Deloya, Cuauhtémoc
Publisher: name: Zenodo
Year: 2022
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Coleoptera
Dynastidae
Ligyrodes

description: Subgenus Ligyrodes Casey, 1915 revised status
Ligyrodes Casey, 1915: 179 (described as genus).
Type species: Scarabaeus relictus Say 1825: 194 by original designation.
Description. (n = 885). Length 16.5–21.8 mm. Humeral width 8–11.5 mm. Head: Clypeus trapezoidal to subtriangular (Fig. 1C). Apical clypeal teeth triangular and widely separated. Ocular canthus rounded, without dorsal setae, with 1–5 ventral setae. Frons with 2 tumescences. Mentum subrectangular (Fig. 2E); not strongly narrowed at apex. Mentum and ligula separated by a suture. Ligula wide; covered with long, dense setae; ligular lobes not fused, with a narrow emargination. Maxillar apical palpomere 1.3 times longer than the second. Maxilla with galea rectangular (2.5 times longer than wide; Figs. 3B, 4C); teeth 3 and 4 diagonal (Fig. 3E). Mandible tridentate (2 apical rounded and lateral long, acute to truncate lobe); apical teeth equal in shape. Labrum subquadrate (Fig. 6C); apex straight; with long, dense setae. Antenna with 10 antennomeres, club long (1.5 times longer than antennomeres 2–7). Pronotum: Apical marginal bead complete. Apex with an inconspicuous, rounded tubercle and a rounded to triangular fovea. Elytra: Inner surface of apex with transverse small tubercles forming 70–77 parallel lines. Wings: RA with dense, large peg-like setae on medial ventral region; with peg-like setae on dorsal surface. Edge of RA 3 with dense setae. Abdomen: Apex of tergite IV with a diagonal line of 11–13 short, transverse, parallel carinae. Sternite VIII emarginate in male; entire in female. Pygidium rugose. Propygidium without stridulatory area. Venter: Prosternum very wide, convex. Propleura with long, sparse setae on anterior and posterior surfaces, medial surface glabrous. Apex of prosternal process suboval, flat, with a deep sulcus; without dorsal setae. Metepisternum with complete, thin carina; inner surface with deep, large punctures, and with long, dense setae; outer surface homogeneously rugose, with long, sparse setae. Metasternum with large, deep, confluent punctures and long, dense setae. Legs: Male protarsus modified; protarsomere 4 with a ventral, carinate, flat projection (Fig. 10C–D); inner claw wide and truncate, with an acute, spine-like projection (Fig. 10E). Protibia tridentate, with an additional basal denticle (Fig. 11D–E), and sometimes a denticle between basal and second teeth, teeth equidistant. Apical margin of mesotibia and metatibia crenulate (Fig. 12D, J). Female genitalia: Subcoxite 1.5 times wider than long (Fig. 13D). Coxite subquadrate (as long as wide); surface flat. Subcoxite wider and longer than coxite. Male genitalia: Phallobase 1.6 times longer than parameres. Parameres without dorsal teeth, with ventral teeth. Internal sac with copulatory lamella and long lamellar spiny belt; accessory lamella U-shaped.
Diagnosis. The subgenus Ligyrodes is differentiated by the following: Trapezoidal clypeus, clypeal teeth small; frontoclypeus with 2 tumescences (Fig. 1C); mentum subrectangular (Fig. 2E); mentum and ligula separate by a suture; ligula wide; covered with long, dense setae; ligular lobes fused, with a narrow emargination; galea with 3 dorsal and 2 ventral teeth (the basal often bifid); pronotum without fovea or tubercle; protibia tridentate, with teeth equidistant; protarsi of male modified, inner claw wide and truncate, with an acute like-spine projection (Fig. 10E), protarsomere 4 with a ventral flat projection (Fig. 10D); internal sac with copulatory lamella and long lamellar spiny belt; accessory lamella U-shaped (Fig. 21D); surface of coxite flat (Fig. 13D). Stridulatory apparatus consisting of a diagonal line of 11–13 short, transverse, parallel carinae on apex of sternite IV and apical inner surface of elytra with transverse small tubercles forming 70–77 parallel lines.
Composition. Three extant species: Ligyrus (Ligyrodes) relictus, L. (Ligyrodes) sallaei, and L. (Ligyrodes) peruvianus. Euligyrus ebenus, which was originally included in Ligyrodes by Casey (1915), is excluded from the subgenus Ligyrodes because although this species also has the protarsi enlarged in male, the shape of the tarsomeres and claws are very different, and there are many characters that support the inclusion of E. ebenus in the genus Euligyrus.
Geographic distribution. One species in North America (United States of America and Canada), one in North and Central America, and only one of its species in South America (restricted to a small area of the Pacific Coast of Ecuador and Peru).
Phylogenetic relationships. The cladistic analysis of Tomarus (sensu lato) showed that this group is more closely related to Ligyrus than Euligyrus, contrary to the idea of Casey (1915).
Taxonomic remarks. Casey (1915) described the genus Ligyrodes to group three species of Ligyrus and seven new species (all currently synonyms of Ligyrus (Ligyrodes) relictus and Ligyrus (Ligyrodes) sallaei) with the male protarsus modified, apex of prosternal process without setae, and the abdominal spiracles of the segments I–III transverse. The genus Ligyrodes was synonymized by Cartwright (1959), and Endrödi (1969) recognized it as a subgenus of Ligyrus but excluded E. ebenus, which he grouped in the subgenus Euligyrus along with E. similis.
Key to the species of the subgenus Ligyrodes
1 Pygidium with deep, large punctures, homogeneously distributed. Apex of metatibia with 13–17 spinules. Species from South America...................................................... Ligyrus (Ligyrodes) peruvianus Endrödi, 1970
- Pygidium with dense rugosity (only on apex or on all the surface).Apex of metatibia with 6–9 spinules. Species from North and Central America...................................................................................... 2
2 Protibia with 3 teeth and a basal denticle, without denticle between basal and second tooth (Fig. 11D). Parameres with ventral teeth acute and long (Fig. 15G). Southeastern Canada and United States of America (east of Rocky Mountains with few records in Texas)............................................................ Ligyrus (Ligyrodes) relictus (Say, 1825)
- Protibia with 3 teeth, a basal denticle, and other denticle between basal and second tooth (Fig. 11E). Parameres with ventral teeth rounded and short (Fig. 15H). United States of America (Texas and southern Arizona) to Panama ...................................................................................... Ligyrus (Ligyrodes) sallaei Bates, 1888
description: Published as part of López-García, Margarita M. & Deloya, Cuauhtémoc, 2022, Cladistic analysis reveals polyphyly of Tomarus (Coleoptera: Scarabaeidae: Dynastinae): new classification and taxonomic revision, pp. 1-119 in Zootaxa 5211 (1) on pages 29-30, DOI: 10.11646/zootaxa.5211.1.1, http://zenodo.org/record/7345007