FNZ 42 - Aphodiinae (Insecta: Coleoptera: Scarabaeidae) - Morphology and diagnostic characters
Stebnicka, ZT 2001. Aphodiinae (Insecta: Coleoptera: Scarabaeidae). Fauna of New Zealand 42, 64 pages.
( ISSN 0111-5383 (print), ; no. 42. ISBN 0-478-09341-1 (print), ). Published 15 Jun 2001
Characterisations of Aphodiinae (Aphodiidae of authors) hitherto given by many authors are far from being exhaustive and concern mainly superficial, often secondary, characters from casual examples of various groups of species. The following, general description is based on all known tribes, of which only four are represented in New Zealand. The principal characters of the subfamily are first listed here in a synoptic form (excluding sexual dimorphism), and then the tribal characters are discussed at greater length.
General characters used in Aphodiinae for identification are illustrated in Fig. 3-6. A number of species have unusual or unique characters which allow them to be identified without needing to use keys and descriptions.
Principal characters of Aphodiinae
Body. Shape and sculpture diverse; length 0.8 mm to 16.0 mm from clypeal apex to elytral apex.
Head. Clypeus dilated to cover mouthparts or shortened, exposing mouthparts or clypeus of intermediate type.
Antenna short, of 9, rarely 8, antennomeres, club circular, ovoid, or elongate, of 3 antennomeres.
Eye very large, moderate in size, vestigial or absent.
Mouthparts. Maxillary endites (galea and lacinia) separate or approximate, consisting of soft, flexible, densely setose lobes; third maxillary palpomere cylindrical, fusiform or triangular, its length varied.
Either: scissorial lobes of mandibles sclerotised, dentate, or truncate; labrum partially sclerotised and more or less exposed in front of clypeus, e.g., Aegialiini (indicates "hard saprophagy" as a component of feeding)
Or: scissorial lobes of mandibles dorso-ventrally flattened, flexible plate-like; labrum membranous, fully covered by clypeus, e.g., Aphodiini (indicates "soft saprophagy or coprophagy" as a component of feeding).
Labrum. Anterior margin evenly rounded, truncate, bilobed or trilobed; inner surface -- epipharynx, consists of various elements and sensory organs (Stebnicka 1985, Stebnicka & Howden 1995, 1996). [Labro-epipharyngeal structures are of some use in species separation, e.g., Aphodiini, and especially indicative at a tribal level].
Pronotum. Rectangular or subquadrate in shape; basal and lateral edges margined or not, and/or crenate, explanate or sulcate or otherwise modified; disc evenly convex or sulcate, fossulate and/or carinate, or with hump.
Scutellum. From very large to minute; shape triangular, pentagonal, semi-oval, or cordate.
Elytra. Striate or not; usually with 10 striae and 10 intervals including sutural ones, or number of striae reduced; rarely elytra non-striate, convergent in sculpture like those of Tenebrionidae, e.g., African Eremazus Mulsant; epipleura gradually narrowed to apices, abruptly narrowed or absent posteriorly, or widely inflexed, e.g., Neotropical Euparixia Brown, Euparixoides Hinton, and Lomanoxia Martinez, or with edge upturned, e.g., Neotropical Selviria Stebnicka (1999a), and Nearctic Hornietus (Stebnicka 2000b); humeral umbone strongly or moderately developed (indicates wings present even if reduced), or humeral area flattened and elytra egg-shaped (indicates wings absent), e.g., Aphodiini, Aegialiini, Psammodiini, and Eupariini; in some species-groups elytra with preapical umbone, e.g., Australian Podotenus Schmidt.
Wings. Fully developed and functional, or non-functional, brachypterous, or absent.
Prosternum. Usually with median tubercle, or with triangular or hastate process.
Mesosternum. Evenly convex or deplanate and/or carinate, or with variously shaped callosities, e.g., Asian-Australian Airapus Stebnicka & Howden, and Neotropical Auperia Chevrolat and Euparixoides Hinton.
Metasternum. Approximately equal to the length of mesosternum (indicates wings present even if reduced), or significantly shorter than mesosternum (frequently wings absent but not always); surface usually with median longitudinal line or furrow, sometimes with pits; posterior plates frequently with metasternal triangle, e.g., Eupariini and Psammodiini.
Abdomen. Five or six sternites visible with intersegmental membranes or sternites coalesced; pygidium covered by elytra or partially exposed, e.g., Proctophanini, Odontolochini, and Eupariini.
Mesocoxae. Approximate (space between mesocoxae smaller than width of mesofemur), or moderately separate (space between mesocoxae equal to width of mesofemur), or widely separate (space between mesocoxae nearly twice as wide as mesofemur); coxal cavities parallel or oblique, elongate, rarely round, convergent in shape with those of Zopheridae (Tenebrionoidea and many other beetles), e.g., Neotropical tribe Lomanoxiini (Stebnicka 1999b).
Metacoxae. Always contiguous; trochanters short, rarely elongate, e.g., Phycocus Broun.
Legs. Middle and hind legs short (femora not or barely visible from above), or moderate in length (femora extending a little beyond body outline), or long (femora projecting for about 1/3 their length).
Profemur short, enlarged, flattened dorso-ventrally; meso- and metafemur parallel-sided or fusiform, sometimes posterior edge dentate.
Protibia short or moderate in length, usually with terminal spur; outer side with 1-5 teeth or serrate, e.g., Asian Setylaides Stebnicka.
Meso- and metatibia cylindrical, or flattened dorso-ventrally or parallel-sided; transverse ridges clearly developed, e.g., Aphodiini, Proctophanini, and some Aegialiini, Psammodiini, and Eupariini, or vestigial, e.g., some Aphodiini, Psammodiini, Aegialiini, and Eupariini, or absent, e.g., Didactyliini, Odontolochini, Eupariini, and Psammodiini, or tibia otherwise sculptured, e.g., Eupariini; apex of meso- and metatibia with two spurs, rarely with one spur; apical spurs of metatibia slender, spatulate, or foliaceous, placed on each side of tarsal insertion, e.g., Aphodiini and Aegialiini, or placed close together below tarsal insertion, e.g., Didactyliini, Odontolochini, Proctophanini, Psammodiini, and Eupariini, or intermediate character state occurs, e.g., some Aphodiini and Eupariini.
External sexual dimorphic characters. Strongly developed to invisible or absent.
Male genitalia. Phallobase of aedeagus usually with dorsal hump, junction of phallobase and parameres usually membranous, e.g., Aphodiini, or phallobase of aedeagus evenly rounded, phallobase and parameres sometimes coalesced, e.g., Eupariini and Psammodiini; apical portion of internal sac membranous, frequently furnished with sclerites and/or spicules.
Female genitalia. Genital plate "stylus" (the divided 10th tergite) and its chaetotaxy is of some use in species separation. However, the only paper comprehensively dealing with genital plates is that by Stebnicka (1977).
Variation. Aphodiinae show considerable individual variation in the proportions and sculpture of the body. Morphological variants include sexual dimorphism, heterogonic or allometric growth, and geographic variation. Some of the differences are apparently partly associated with size and hence could be considered as allometric. Noticeable geographic variation may be expressed either externally, often in the secondary sexual characters, or in the shape of male genitalia. The latter type of variation can make it difficult to determine the status of allopatric populations.
Larvae (white grubs). Body C-shaped, with soft cuticle, except for head capsule and mouthparts. Head usually with a single ocellus on either side, rarely ocelli absent; epicranial suture usually distinct; clypeus transverse, labrum trilobed, freely articulated. Antenna with four (sometimes with five) antennomeres, the last reduced in size, the third usually with conical sensory process. Mandibles asymmetrical; maxilla with galea and lacinia distinctly separate, but often close together, stipes with a row of stridulatory teeth, or without teeth. Legs well developed, with four podites, prothoracic pair shorter. Dorsum of thoracic and abdominal segments plicate; openings of respiratory plates of thoracic spiracles facing posteriorly, those of abdominal spiracles facing ventrally or cephaloventrally; last abdominal segment variously shaped, raster with palidium, oocasionally palidium indistinct or absent.
Pupa of exarate type, the appendages free.
The immatures have been treated by Ritcher (1966).
Diagnostic characters for tribes found in New Zealand
Aphodiini: body glabrous or covered with hairs; clypeus dilated to cover mouthparts; elytron lacking basal bead; abdominal sternites not fused, with intersegmental membranes; pygidium not exposed, covered by elytra, without scabrous area basally (Fig. 4); mesocoxae approximate, space between mesocoxae usually smaller than width of mesofemur; transverse ridges of meso- and metatibia well developed or occasionally vestigial, apical spurs slender, separated, located on each side of tarsal insertion or nearly so (Fig. 6); phallobase of male aedeagus usually with dorsal hump (Fig. 44) or arcuately rounded (Fig. 46); labro-epipharyngeal complex as in Fig. 33-35.
The male genitalia and the epipharyngeal structures of Aphodiini are usually distinctive and often very useful in identification of species.
Psammodiini: body glabrous or covered with setae; clypeus dilated to cover mouthparts; pronotum usually unevenly convex with transverse ridges and furrows, or their vestiges, rarely evenly convex; elytron with or without basal bead; abdominal sternites coalesced, rarely fine intersegmental membranes occur; posterior coxal plates frequently with metasternal triangle, pygidium partially exposed or covered by elytra; mesocoxae approximate or slightly separate, space between mesocoxae usually smaller or equal to width of mesofemur; meso- and metatibia short and robust or elongate and slender, transverse ridges vestigial or lacking, rarely distinctly developed, sometimes metatibia furnished with denticles or tubercles; apical spurs spatulate or slender, located close together below tarsal insertion; phallobase of male aedeagus without dorsal hump (Fig. 47, 48); labro-epipharyngeal complex as in Fig 36.
Psammodiini are most closely related to the Eupariini and either the external morphological characters and/or those of the male genitalia of some groups of species in each tribe overlap. The epipharyngeal structures of Psammodiini differ from the general scheme of those in the Eupariini and are usually sufficient for tribal placement. The differences are evident chiefly in the shape and structure of the anterior median process and in the kinds of sensilla.
Proctophanini: body usually glabrous; clypeus dilated to cover mouthparts; elytron lacking basal bead; abdominal sternites coalesced without intersegmental membranes; posterior coxal plates with metasternal triangle, pygidium fully or partially exposed, usually with longitudinal carina at middle; mesocoxae approximate or slightly separated, space between mesocoxae smaller than width of mesofemur; transverse ridges of meso- and metatibia distinct, apical spurs slender, placed close together below tarsal articulation; phallobase of male aedeagus without hump (Fig. 49, 50); labro-epipharyngeal complex as in Fig. 37, 38.
The characters of the male genitalia are useful for identification of species; the epipharyngeal structures are similar to those present in Eupariini. Proctophanini is primarily an Australian-African tribe representing a transitional link between the Aphodiini and the Eupariini. The Australian genus Proctophanes and African genera Australaphodius Balthasar, Harmogaster Harold, and Drepanocanthus Péringuey share similar character states and are considered to constitute a separate tribe, the Proctophanini (Stebnicka & Howden 1995).
Eupariini: body glabrous or covered with setae; clypeus dilated to cover mouthparts; pronotum usually evenly convex or with slight lateral swellings, rarely with median hump; elytron with basal bead; abdominal sternites coalesced; posterior coxal plates usually with metasternal triangle, pygidium fully or partially exposed with transverse carina and scabrous area basally (Fig. 27); mesocoxae approximate, slightly separate or widely separate, in some species space between mesocoxae twice as wide as mesofemur; meso- and metatibia cylindrical or flattened, transverse ridges distinct, vestigial or lacking, sometimes metatibia with longitudinal carinae or rows of denticles or tubercles; apical spurs usually slender, placed close together below tarsal insertion; phallobase of male aedeagus usually without hump (Fig. 51-59); labro-epipharyngeal complex as in Fig. 39-43.
Very few descriptions of species of Eupariini include the characters of the male genitalia and of the clypeo-labrum. These characters have been examined on a world basis by the author for many species belonging to various taxonomic groups. It has been found that the characters of aedeagus, and the epipharyngeal structures of the Eupariini differ in general from those of the Aphodiini but that they are less useful at the species level. In some euparine groups, the shape of the epipharynx is similar to that of the Psammodiini, but the structures of the anterior median process and some kinds of sensilla are usually sufficient to distinguish the representatives of these two tribes.