Characteristics
Form elongate oval. Labrum and mandibles prominent, produced beyond apex of
clypeus, clypeus with or without weak horn. Antenna with 9 segments, antennal
club with 3 segments, segments not tomentose. Anterior coxae transverse. Pronotum
with or without anterior projections. Scutellum exposed. Metasternum longer
than abdominal sternites. Metatibia with apical spines separated by basal metatarsal
segment (Aclopus) or not (mesad and adjacent in Neophaenognathus).
Tarsal claws on all legs not independently movable, claws equal in length or
size, claws with a weak basal tooth. Onychium cylindrical with 2 setae. Pygidium
exposed beyond apices of elytra. According to Arrow (1909) the genitalia are
poorly sclerotized and do not provide characters for identification.
Classification Status
The subfamily Aclopinae was established by Blanchard 1850. It originally included
two genera, Aclopus Erichson and Phaenognatha Hope. These two genera were placed
in Glaphyridae by Erichson (1845-1847) and moved to the Melolonthinae by Lacordaire
based on the position of the spiracles. Later Arrow (1909) found that the spiracles
of one species Aclopus brunneus Erichson were of the laparostict type, condition
in which most of the spiracles are on the pleural membrane between on the tergites
and sternites and it is characteristic of scarabs that feed on dung, carrion
hides or feathers (i.e. Scarabaeinae, Aphodiinae); the alternative is the pleuristic
condition where most of the abdominal spiracles are situated in the upper portion
of the sternites present in scarabs that feed primarily on leaves, roots, or
decaying wood (i.e. Rutelinae, Dynastinae, and Cetoniinae). However, Ohaus (1909)
found that the spiracles of the male were situated in the membranes connecting
the dorsal and ventral segments (laparostict type), but the last four spiracles
of the female were situated in the chitin of the ventral segments (pleurostict
type). According to Arrow (1909) this difference may be due to the possible
fact that the females are flightless. In 1915 Arrow described a third genus,
Xenaclopus, with one species, X. borneensis Arrow, from Borneo. Iablokoff-Khnzorian
(1977) hypothesized that the Aclopinae are most closely related to the Hybosorinae,
Ochodaeinae, and "Loxsticti" (Euchirinae, Cetoniinae, Dynastinae,
Rutelinae). Allsopp (1981, 1983) revised the Australian species and created
a new genus, Neophaenognatha, for the New World species of Phaenognatha. Nikolajev
(2004-2005) was the last to treat the group, he divided the subfamily in two
tribes, Aclopini includding all extant taxa plus two monotypic genera from the
Jurassic and Cretaceous respectively, and Holcorobeini that includes four genera
and 17 fossil species. These records make the Aclopinae among the oldest groups
of Scarabaeoidea. Although the systematic placement of the fossil taxa (at least
some) included in Nikolajev´s paper as Aclopinae (Nikolajev 1992, 2004,
2005) are very doubtfull, if they are in fact aclopines, Aclopinae would be
among the oldest scarabs ever recorded in literature. These fossil records place
the origin of the subfamily Aclopinae and Scarabaeoids back to minimum of 144
mya (see Krell 2000).
Distribution
The subfamily includes four genera and 19 species that are distributed in northern
Australia, Borneo, and southern South America (Allsopp 1983). Two genera occur
in the New World: Neophaenognathus (4 species) and Aclopus
(6 species). Catalog: Arrow 1912.
New World Genera of Aclopinae
Neophaenognatha
Allsopp 1983
Includes four species distributed in Argentina (Allsopp 1983).
Aclopus Erichson 1835
Includes six species that are distributed Brazil and Argentina.
Ecology
Little is known of the ecology and biology of this small group of scarabs. In
Australia, adults of Phaenognatha are usually taken at lights (Lawrence and
Britton 1991). Although few female specimens of Aclopinae are known and no literature
exists regarding females, Arrow (1909) noted that certain morphological characters
suggest that females may be flightless. Allsopp (1983) also noted character
similarities that the Aclopinae share with other scarabaeoids that spend most
of their lives below ground, including reduced posterior wings and posterior
tarsi, inflated abdomen, and absence of a clypeal horn.
Larvae
Larvae of the Aclopinae have not been described.
References Cited
ALLSOPP, P. G. 1981. Revision of the Australian species of
Phaenognatha Hope (Coleoptera: Scarabaeidae: Aclopinae). Journal of the Australian
Entomological Society 20: 185-195.
ALLSOPP, P. G. 1983. Neophaenogantha, a new genus for the Neotropical
species of Phaenognatha Hope (Scarabaeidae: Aclopinae) with the description
of N. capella n. sp. and designation of lectotypes. Coleopterists Bulletin 37(3):
208-211.
ARROW, G. J. 1909. XV. On the characters and relationships
of the less-known groups of Lamellicorn Coleoptera, with descriptions of new
species of Hybosorinae, etc. Transactions of the Entomological Society of London
57: 479-507.
ARROW, G. J. 1912. Scarabaeidae: Pachypodinae, Pleocominae,
Aclopinae, Glaphyrinae, Ochodaeinae, Orphninae, Idiostominae, Hybosorinae, Dynamopinae,
Acanthocerinae, Troginae. Coleopterorum Catalogus pars 43, W. Junk, Berlin.
66 pp.
BLANCHARD, E. in MILNE-EDWARDS ET AL. 1850. Museum d'Histoire
Naturelle de Paris: Catalogue de la Collection Entomologique. Classe des Insectes,
Ordre des Coleopteres. Vol. 1. Gide & Baudry, Paris. 240 pp.
ERICHSON, W. F. 1845-1847. Natureschichte der Insecten Deutschlands.
Erste Abtheilung, Coleoptera, Vol. 3: 1-800. Verlag der Nicolaischen Buchhandlung,
Berlin.
IABLOKOFF-KHNZORIAN, S. M. 1977. Uber die Phylogenie der Lamellicornia
(Insecta, Coleoptera). Entomolo. Abh. (Dresden) 41: 135-200.
LAWRENCE,
J. F. and E. B. BRITTON. 1991. Coleoptera. The Insects of Australia,
2nd edition, Volume 1, , pp. 543-683. Melbourne University Press, Carlton.
LAWRENCE, J. F. AND A. F. NEWTON, JR. 1995. Families and subfamilies
of Coleoptera (with selected genera, notes, and references and data on family-group
names), pp. 779-1006. In J. Pakaluk and S. A. Slipinski (eds.), Biology, Phylogeny,
and Classification of Coleoptera. Papers Celebrating the 80th Birthday of Roy
A. Crowson. Muzeum i Instytut Zoologii PAN, Warszawa, Poland.