Arctodium Burmeister, 1844

Hawkins, Shauna Joy, 2006, A revision of the Chilean tribe Lichniini Burmeister, 1844 (Coleoptera: Scarabaeidae: Melolonthinae), Zootaxa 1266 (1), pp. 1-63 : 31-33

Genus Arctodium Burmeister, 1844

( Figs. 2 , 4c , 5a , 6a , 7a , 8a–d , 9c , 11 , 12 )

Arctodium Dejean 1833: 167 (nomen nudum).

Cratoscelis Erichson 1835: 267 (synonym).

Arctodium Burmeister 1844: 9 (valid name).

Catalog

Arctodium: Dejean 1833: 167 (first usage); Dejean 1836: 186 (catalog); Lacordaire 1856: 161 (listed as a synonym of Cratoscelis ), 162 (catalog); Harold 1869: 1094 (catalog); Chapin 1938: 80 (catalog listing as invalid name); Hawkins 2004 (online catalog listing as invalid name).

Cratoscelis: Erichson 1835: 267–269 (original description); Laporte 1840: 154, 155 (catalog); Blanchard 1845: 210 (catalog); Curtis 1845: 455 (catalog, notes on mouthparts); Blanchard 1850: 52, 53 (catalog, new species descriptions); Erichson 1848: 718 (key, taxonomic notes); Solier 1851: 119–122 (redescription and diagnoses); Lacordaire 1856: 159 (taxonomic notes), 161 (redescription), 162 (comparison with Lichnia ); Philippi & Philippi 1864: 326 (comparison of species, new species description); Redtenbacher 1868: 61 (catalog, new species description); Harold 1869: 1094 (catalog); Philippi 1887: 685 (catalog); Germain 1911: 68 (catalog); Arrow 1912: 6 (catalog); Chapin 1938: 80 (name invalidated because it is a homonym, type species designation); Gutiérrez 1943: 146 (taxonomic note); Blackwelder 1944: 216 (checklist); Machatschke 1959: 528–532, 540–542, 544 (comparative notes and figures), 539 (distribution map); Medvedev 1960: 191 (taxonomic notes); Ritcher 1969: 875, 876, 878 (comment on spiracles); Iablokoff­ Khnzorian 1977: 174, 175 (taxonomic notes); Nel & Scholtz 1990: 11 (note on distribution); Scholtz 1990: 1052 (morphological notes); Browne & Scholtz 1996: 30 (note on distribution and taxonomic placement); Hawkins 2004 (online catalog listing as synonym).

Arctodium: Burmeister, 1844: 9–10 (first usage of name with available species names); Chapin 1938: 81 (stated name as replacement for Cratoscelis , type species designation); Gutiérrez 1943: 146, 147, 151 (taxonomic notes); Carlson 2001 (online taxonomic information); Hawkins 2004 (online catalog).

Type species Cratoscelis vulpina Erichson, 1835 by subsequent designation ( Chapin 1938). Etymology

The name Arctodium likely comes from the Latin word arctos, meaning bear or bearlike ( Brown 1956). The gender is neuter.

Description

Male. Length 4.5–12.5 mm; width 3.0–8.0 mm. Color: Head, pronotum, and scutellum black; venter, elytra, legs, pygidium, and setae variable. Head: Head strongly deflexed. Frons slightly concave. Surface setosely punctate; punctures and setae variable. Labrum clearly visible in dorsal view, exposed part in dorsal view 2/3 as long as clypeus. Mandibles protruding anteriorly beyond labrum; apices with 2 apical teeth, strongly reflexed ( Fig. 6a ). Maxilla with moderately long galea ( Figs. 5a , 7a ), galea 1/2 to subequal in length to head (including mouthparts), setose; setae curved, short, dense, forming row, pale yellow to light tan. Maxillary palpi 4­segmented; segment 1 small, 1/2 length of 2, 2–3 cylindrical, equal in length, 4 fusiform. Labium deeply grooved longitudinally. Labial palpi 3­segmented: segments 1–2 conical, 3 fusiform. Eye completely divided into dorsal and ventral sections by canthus. Antenna 9­segmented. Pronotum: Surface setosely punctate, punctures and setae variable. Disc with weak, median, longitudinal groove. Lateral margins with poorly developed bead. Posterior margin strongly projected posteriorly at middle. Elytron: Length short, not covering pygidium. Propygidium: Surface exposed, covered with long, dense, white setae; setae overlaying basal 1/5 of pygidium (covered by elytra in some specimens), apices of setae forming straight row. Pygidium: Lateral and apical margin with bead. Apex rounded. Venter: Abdomen with 7 exposed segments; segments setosely punctate, punctures and setae variable. Pleural membrane with 6 spiracles. Tergite with 1 spiracle. Legs: Surface setosely punctate; punctures and setae variable. Protarsomere 1 3/4 length of 2, 2 long, subequal in length to 5, 3–4 short, sub­globose, subequal in length to each other; 5 twice as long as 4. Metatibial apex with 2 spurs and 1 spine; spine between 2 spurs, long, attenuate, with sharp point at apex ( Figs. 8a–c ). Mesotarsomere and metatarsomere 1 longer than 2–4, 2–4 subequal to each other, 5 subequal to 2–4. Tarsal claws simple. Unguitractor plate with sides parallel, with 2 apical setae. Parameres: Figs. 9c .

Female. Females differ from males in the following respects: length 5.0–12.0 mm; width 3.0– 6.5 mm. Legs: Metatibial apex with 1 spine; spine short, broadly attenuate, with blunt point at apex ( Fig. 8d ).

Diagnosis

Arctodium is differentiated from Lichnia by the shorter galea in Arctodium that is less than half the length of the entire body ( Figs. 5a , 7a ). In Lichnia the galea is more elongated and extends at least half the length of the entire body ( Figs. 5b , 7b ). Also, the mandible of Arctodium is toothed ( Fig. 6a ), whereas the mandible of Lichnia is smooth and rounded ( Fig. 6b ). The distribution range for Arctodium ( Figs. 11 , 12 ) extends further south than that of Lichnia ( Fig. 10 ).

Distribution

Species of Arctodium are found in central Chile from Region V (Valparaíso) to Region IX (La Araucania) ( Figs. 11 , 12 ) .

Remarks

According to Chapin (1938), Arctodium Burmeister should replace Cratoscelis Erichson as the valid name of the genus. However, subsequent authors still incorrectly used Cratoscelis as the valid name. I agree with Chapin that Cratoscelis Erichson is not a valid name, because Lucas (1834) previously used the name Cratoscelis in connection with a plate of figures, including the spider species Cratoscelis rufipes Lucas and Cratoscelis nigripes Lucas ( Araneae : Sicariidae ). There is no description of these species, but the International Code of Zoological Nomenclature states (Article 12.1) that for a genus name published before 1931 to be valid, the publication must include a description, a definition, or an indication of the taxon (International Commission on Zoological Nomenclature 1999). Furthermore, the Code states (Article 12.2.7) that the publication of a genus name in conjunction with an illustration is sufficient as an indication. Therefore Cratoscelis Erichson, 1835 is a junior homonym of Cratoscelis Lucas, 1834 , and Arctodium Burmeister should be the valid name.

Arctodium was proposed by Dejean (1833) in his catalog with A. villosum Dejean as the only species. However, there was no description, definition, or indication of A. villosum , and therefore the name Arctodium Dejean is a nomen nudum according to Article 12 of the Code (International Commission on Zoological Nomenclature 1999). It was Burmeister (1844) who first used the name as an invalid synonym of Cratoscelis Erichson in association with described species ( A. discolor and A. vulpina ), and it is to Burmeister (1844) that we attribute the name under Article 11.6.1 of the Code (International Commission on Zoological Nomenclature 1999).

Figures

FIGURE 2. Arctodium vulpinum (Erichson) male.

FIGURES 4a–c. Dorsal view of antenna showing length of club. a) Lichnia limbata male; b) L. limbata female; c) Arctodium mahdii male.

FIGURES 5a–b. Dorsal view of maxilla showing length of galea. a) Arctodium discolor; b) Lichnia limbata.

FIGURES 6a–b. Dorsal view of labrum and mandibles showing form of the mandibles (a) dentate, Arctodium vulpinum or (b) rounded, Lichnia limbata.

FIGURES 7a–b. Lateral view of beetles showing length of galea. a) Arctodium vulpinum; b) Lichnia limbata.

FIGURES 8a–d. Metatibial apex showing apical spine (arrow) and adjacent spur. a) Arctodium planum male; b) A. mahdii male; c) A. vulpinum male; d) A. vulpinum female.

FIGURES 9a–c. Caudal (i) and lateral (ii) views of parameres. a) Lichnia gallardoi; b) L. limbata; c) Arctodium discolor.

FIGURE 10. Map of central Chile showing distribution of Lichnia gallardoi and L. limbata.

FIGURE 11. Map of central Chile showing distribution of Arctodium discolor and A. planum.

FIGURE 12. Map of central Chile showing distribution of Arctodium vulpinum and A. mahdii.