.......Arctodium mahdii Hawkins, 2006

Specimen image not available at this time
Distribution of Arctodium mahdii.
Dorsal view of antenna showing length of club. a) Lichnia limbata male; b) L. limbata female; c) Arctodium mahdii male.

Description.Arctodium mahdii is easily distinguished from all other species of Arctodium because of its smaller size; it is the only species that is less than 6.5 mm long. It is also the only species of Arctodium in which the spine on the metatibial apex is shorter than the adjacent spurs. In all other species of Arctodium, the spine on the metatibial apex is longer than the adjacent spur. The male antennal club is longer in proportion to its body size than all other species of Arctodium, but it is not as long as the antennal club of males of Lichnia limbata. Elytral and setal color are variable in A. mahdii, however the elytra of males are most often reddish-black to black, and setae on all parts of the body are usually dark brown, black, or gray. The elytra of females are more often brownish orange, and the setae on all parts of the body are most often golden yellow with some black setae on the apex of the head, mouthparts, and eye canthus.

Remarks. Arctodium mahdii has characters that show affinities with species of both Lichnia and Arctodium. Because of its small size, A. mahdii may superficially resemble species of Lichnia if generic characters are not checked with a microscope. Arctodium mahdii can be easily distinguished from either species of Lichnia by examining the apex of the mandibles which are rounded and without teeth in Lichnia versus bidentate in A. mahdii.The male antennal club of A. mahdii is sexually dimorphic as in L. limbata, and the female protibia are expanded while the male protibia are slender as in both species of Lichnia. Also, the spine on the tibial apex of males of A. mahdii is smaller than in males of other species of Arctodium, but it is more strongly modified into a spine than in males of Lichnia. Arctodium mahdii may have an evolutionary relationship intermediate to the two genera. Because in A. mahdii the galea is only slightly elongate and the apex of the mandibles are bidentate, and because the genitalia are remarkably similar to all other species of Arctodium and different from Lichnia, this species was placed in the genus Arctodium by Hawkins (2006).

Distribution. Central Chile Region VII (Maule) to Region IX (La Araucania). A great number of specimens in collections originate from Fundo Malcho, which used to be forested at the time when the specimens were collected. However, this area is now almost entirely deforested and has been developed into pine plantations (Paulsen 2005).

Phenology. October to February.

Biological Data. For unknown reasons, females are rarely collected.

References:
Hawkins, S. J. 2006. Revision of the Chilean tribe Lichniini Burmeister, 1844 (Coleoptera: Scarabaeidae: Melolonthinae). Zootaxa 1266: 1-63.

Paulsen, M. J. 2005. A revision of the southern South American stag beetles of the genus Sclerostomus Burmeister (Coleoptera: Scarabaeoidea: Lucanidae). Zootaxa, 1060, 1–26.