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Scarabaeoidea of Southern South America Links |
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Scarab Guide Links
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Arctodium mahdii Hawkins, 2006
Arctodium mahdii Hawkins, 2006: 37. |
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Map of central Chile showing distribution of Arctodium vulpinum
and A. mahdii. |
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Description. Holotype. Male. Length 6.5 mm, width 3.9 mm. Color: All body parts reddish black.
Head: Surface punctate; punctures small, dense, setose; setae long, moderately dense,
black. Labrum with surface punctate; punctures small, dense, setose; setae short, half as
long as clypeal setae, dense, black. Mandibular external surface with moderately long,
dense, black setae. Maxillary palpi with short, black apical setae on all segments except
last. Labial margins with moderately long, dense, black setae. Labial palpi with short,
black, setae at apex of all segments except last. Eye canthus setose; setae long, dense,
black. Antenna with pedicel setose, elongate, segment 2 globular, 3-6 subequal in length,
7-9 lamellate; club slightly longer than segments 2-6. Pronotum: Surface
punctate; punctures small, moderately dense, with long, dense, black setae. Lateral
margins setose; setae long, dense, black. Posterior margin setose; setae moderately long, dense, grayish black. Scutellum: Surface setose; setae moderately long, moderately dense,
gray. Elytron: Form moderately wide, less than half as wide as long. Surface slightly
convex, punctate; punctures small, moderately dense medially, dense laterally, setose; setae short medially, moderately long laterally, black. Propygidium: Surface exposed,
covered with moderately long, dense, grey setae; setae overlaying basal 1/5 of pygidium),
apices of setae forming straight row. Pygidium: Surface slightly concave apically, setose;
setae long, moderately dense, black. Venter: Thorax, mes- and metepisternum punctate;
punctures small, sparse, with moderately long, gray setae. Abdominal segments sparsely
setose; setae long, gray. Legs: Surface setose; setae long, dense, gray. Protibia slender,
with 3 outer teeth and 1 inner tooth. Protibial spur 1.5 times length of first tarsal
segment. Metafemur slightly expanded. Metatibial apex with 2 spurs, 1 spine; spine
between 2 spurs, spine shorter than spurs, narrow, attenuate at apex. Parameres:
Fig. 9c. Allotype. Female. Length 6.5 mm, width 4.2 mm. As holotype except in the following
respects. Color: Elytra brownish orange, legs reddish brown, setae on head, clypeus,
elytra, pygidium, venter, abdomen, and legs golden yellow. Head: Antennal club short,
slightly shorter than or subequal to segments 3-6 . Legs: Protibia expanded. Metatibial apex with 1 spine; spine short, shorter than adjacent spurs, not narrow,
broadly attenuate at apex.
Variation. Male: length 5.0-6.5 mm, width 3.4-4.2 mm.
Female: length 5.2-6.5, width
3.3-4.5. Paratypes differ from the holotype and allotype in the following respects. Color:
Elytra variable: brownish orange, reddish black, or black. Setae on head, clypeus, elytra,
pygidium, venter, abdomen, and legs moderately long to long, color variable: black, dark
brown, gray, or golden yellow.
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Etymology.
Arctodium mahdii is named after my husband Mahdi, for his support and
encouragement of my work on scarab beetles. |
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Diagnosis.
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. 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. |
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Remarks.
While elytral and setal color are variable (see description) in A. mahdii, the elytra of
males are more 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. However, the full variation of color as
stated in the species description can occasionally be seen in both sexes.
Arctodium mahdii has characters that show affinities with species of both Lichnia and
Arctodium. Arctodium mahdii and species of Lichnia are similar in size. 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, I place this
species in the genus Arctodium. Furthermore, despite the many morphological differences
between A. mahdii and the other species of Arctodium, I have not designated it as a new
genus because of the genitalia, which are remarkably similar to all other species of
Arctodium and different from Lichnia.
Many collections have specimens of A. mahdii labeled as C. villosa (= A. vulpinum),
but Blanchard’s type specimen of C. villosa does not exhibit any of the apomorphic
characters of A. mahdii.
For unknown reasons, females are rare in collections. Of the 272 specimens examined,
only four were female. |
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Distribution.
Central Chile Region VII (Maule) to Region IX (La Araucania) (Fig. 12), especially
abundant at Fundo Malcho, which used to be forested at the time when the specimens
examined were collected. However, this area is now almost entirely deforested and has
been developed into pine plantations (Paulsen 2005). |
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Locality data.
274 specimens were examined from AMNH, BMNH, CASC, CMNC, CNCI, FSCA,
FMNH, JEBC, JMEC, MNHN, MNNC, TAMU, UCCC, UMRM, UNSM, USNM,
VMDC, ZMHB.
CHILE. REGION VII (MAULE) (201): Fundo Malcho (201). REGION VIII (BIOBÍO) (45): Alto Caicupil (3), Alto de Nahuelbuta (1), Atacalco (2), Cabreria (3),
Caramavida (16), Chillan (2), Coihueco (8), Coimallin (2), Nahuelbuta (1), Peillén Pille
(1), Pilim Pili (4), Temuco (1), Tregualemu (1). REGION IX (LA ARAUCANIA) (28):
Angol (1), Cautin (3), Coñaripe (3), Los Lleuques (4), Nahuelbuta (1), Pucón (15),
Temuco (1).
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Temporal data.
January (29), February (2), October (64), December (171). |
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Excerpt from:
Hawkins, S. J. 2006. A revision of the Chilean tribe Lichniini Burmeister, 1844
(Coleoptera: Scarabaeidae: Melolonthinae). Zootoaxa 1266:1-63. |
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