Scarabs, stag beetles, dung beetles, rain beetles, etc.D. Jonathan Browne and Clarke H. Scholtz
This tree diagram shows the relationships between several groups of organisms.
The root of the current tree connects the organisms featured in this tree to their containing group and the rest of the Tree of Life. The basal branching point in the tree represents the ancestor of the other groups in the tree. This ancestor diversified over time into several descendent subgroups, which are represented as internal nodes and terminal taxa to the right.
You can click on the root to travel down the Tree of Life all the way to the root of all Life, and you can click on the names of descendent subgroups to travel up the Tree of Life all the way to individual species.close box
Perhaps the most well-known features of adult scarabaeoids are their 3-7 segmented, fan-like or lamellate antennal club and powerful legs armed with teeth on the outer edge, an adaptation for digging.
The larvae are typically C-shaped when immobile.
In addition adult scarabaeoids are distinguished by: a highly modified, burrowing prothorax, with large coxae (almost always with concealed trochantins and closed cavities) and usually dentate tibiae with only one spur; hind wings with reduced venation and strong intrinsic spring mechanism for folding; a lamellate antennal club; no hind coxal plates; the second abdominal sternite represented by a lateral portion only; the eighth tergite forming a true pygidium and not concealed by the seventh; four Malpighian tubules (Lawrence & Britton 1991); and 1Ax-2Ax articulation mediated by a well-developed 2Ax medial groove and dorsal ridges (Browne 1993).
Larvae are grub-like with well-developed antennae and legs, no urogomphi, and usually, cribriform spiracles (Crowson 1967, Borror et al. 1989).
Scarabaeoids feed on most types of dung and a wide range of plant and animal matter, from detritus through lower plants to virtually all higher plant tissues and carrion to predation on other insects. Their habits range from free-living through fairly sophisticated forms of brood care to sub-social behaviour (Borror et al. 1989, Scholtz 1990).
The fossil record of scarabaeoids is discussed on a separate page.
There have been many broadly based comparative studies covering most major structures including antennae (Iablokoff-Khnzorian 1977), antennal sensilla (Meinecke 1975), eye (Caveney 1986), mouthparts (Nel & Scholtz 1990), prothorax (Hlavac 1975), coxae (Hlavac 1975, Ritcher 1969c), spiracles (Richer 1969a, 1969b), wing venation (Crowson 1967, Iablokoff-Khnzorian 1977), alimentary canal (Scholtz, unpublished), metendosternite (Crowson 1938, Iablokoff-Khnzorian 1977), male genitalia (d'Hotman & Scholtz 1990a, 1990b), female genitalia (Scholtz, unpublished, Holloway 1972, Lawrence & Newton 1982, Tanner 1927), ovarioles (Ritcher & Baker 1974), karyotype (Smith & Virkki 1978, Yadav & Pillai 1979), central nervous system (Scholtz, unpublished, Iablokoff-Khnzorian 1977), spermatozoan number (Virkki 1969), Malpighian tubules (Caveney 1986), larvae (Areekull 1957, Costa et al. 1988, Hinton 1967, Ritcher 1966) and neuropeptides (Browne, unpublished).
Scarabaeoid family and subfamily definitions were established by the beginning of this century as were some notions on the evolutionary progression of the taxa. However, these concepts were often intuitively derived (confirmation of many of these traditional ideas has subsequently occurred). The first tangible contributions towards a phylogeny of the Scarabaeoidea were provided by the numerous morphological studies of the superfamily. Apart from providing vital morphological data a rough evolutionary picture of the superfamily also emerged.
The first attempt to apply modern cladistic techniques to the analysis of relationships within the group as a whole was that of Howden (1982). This study, based on 39 characters from 17 taxa, focused on the phylogenetic position of Taurocerastinae (Geotrupidae) in relation to many other scarabaeoid taxa. The study did fulfill one of its major functions in stimulating further investigations of the relationships among the various higher taxa.
The next major study, that of Scholtz (1990), provided a comprehensive review of the available scarabeoid literature. Although the main purpose of this work was to make available a complete data set for future cladistic analysis, some discussion of evolutionary trends was also included.
Browne (1993) and Browne & Scholtz (1995) examined the evolution and morphology of the hind wing articulation, base and venation. Although this study examined all higher scarabaeoid taxa (13 families, most subfamilies, 250 genera) and all taxa identified by Scholtz (1990) as being of uncertain phylogenetic status for the first time, it was very limited in that the resulting phylogram was based on only three character complexes (73 characters). However, there is strong evidence that wing related characters are the most reliable of all structures in elucidating relationships among higher taxa (Kukalov?-Peck 1983).
To date the most comprehensive study is that of Browne & Scholtz (in preparation). They considered all major character suites, 134 characters, which supported most of the relationships presented by Browne (1993) and Browne & Scholtz (1995). The main conclusions of this study are given in the phylogram above.
Although relationships among many taxa are controversial, recent analyses, especially those of Howden (1982), Browne (1993), Scholtz et al. (1994), Browne & Scholtz (1995, in preparation) have resolved the following:
- Glaresidae is the sistergroup of the remaining scarabaeoids and likely reflects the ancestral scarabaeoid due to its large number of unusual plesiomorphies.
- Lucanidae and Diphyllostomatidae together form the sistergroup of the Passalidae.
- Geotrupidae (Geotrupinae, Taurocerastinae and Lethrinae), Hybosoridae, Ceratocanthidae and Ochodaeidae together form the sistergroup of Passalidae, Lucanidae, Diphyllostomatidae, Trogidae, Bolboceratidae, Pleocomidae and Glaphyridae. Together these taxa form the sistergroup of the Scarabaeidae.
However, the following are still heatedly debated:
- Monophyly of the Geotrupidae. Howden (1982) includes Bolboceratinae, Geotrupinae, Taurocerastinae and Lethrinae in this family. Scholtz & Browne (in press) present evidence that this family is polyphyletic and elevated Bolboceratinae to familial status.
- The position of Glaphyridae. Once accorded superfamily status (Hinton 1967) this family has more commonly been placed among the so-called "intermediate" scarabaeoids (Geotrupidae, Hybosoridae, Ceratocanthidae and Ochodaeidae)(Scholtz 1990). Recent evidence suggests that it is a member of the so-called "primitive" scarabaeoids (Passalidae, Lucanidae, Diphyllostomatidae, Trogidae, Bolboceratidae, Pleocomidae and Glaphyridae).
- Scarabs, stag beetles, dung beetles, rain beetles, etc.
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D. Jonathan Browne
University of Cape Town, South Africa
Clarke H. Scholtz
University of Pretoria, South Africa
All Rights Reserved.
Citing this page:
Browne, D. Jonathan and Clarke H. Scholtz. 1995. Scarabaeiformia. Scarabaeoidea. Scarabs, stag beetles, dung beetles, rain beetles, etc.. Version 01 January 1995 (under construction). http://tolweb.org/Scarabaeoidea/9077/1995.01.01 in The Tree of Life Web Project, http://tolweb.org/