Dung scarabs

Scarabaeidae, Scarabaeinae (= Coprinae).

Nahuatl: Mayameh, sing, mayatl.

Feeding on feces is a fundamental feature of the biology of this scarab subfamily which determines behavior, distribution, morphology, and development. Adults are attracted to fresh animal excrement by its odor and feed directly on it or remove portions on which to lay their eggs and provide for larval nutrition (Halffter and Edmonds 1982). The fact that this food source abounds principally in grasslands has largely determined the prevalence of these beetles there, in association with large grazing mammals and their predators, although it would be incorrect to assume that they are not abundant in kind and number in forest habitats as well (Howden and Nealis 1975). Here, especially smaller types in several genera (e.g., Canthidium, Eurysternus, fig. 9.6a) are commonly observed perching on leaves in low vegetation (Howden and Nealis 1978). Several functions for this behavior have been suggested, including resource-partitioning strategy, assessment of predator density

nearby, mimicry display, and thermoregulation (Young 1984), but none has been conclusively demonstrated.

Various members of this group digress from coprophagy and utilize carrion (necro-phagy) or decomposing vegetable matter (saprophagy) as food. A very specialized example of the latter is the consumption of debris that accumulates in the nests of leaf cutter ants (Alia) by such genera as Liatongus and Onthophagus. An extraordinary feeding specialization is that of a Brazilian Canthon that attacks ants of the same genus (Navajas 1950). A few even inhabit the hair of sloths (Uroxys and Trichillum; Ratcliffe 1980) and monkeys (Glaphyrocanthon).

Adults are small to large, well-armored beetles that are very compactly built, many almost spherical in shape. The antennal club has only three segments. Most possess a shovel-shaped head and fossorial forelegs, useful also in cutting, molding, and burying dung. Many are colored brightly in metallic green, blue, or coppery hues, some stunningly so.

The eyeless, heavy-jawed larvae are C-shaped, as is typical in the scarabs, but they also have a characteristic "hump," or dorsal enlargement of the middle abdominal segments. The projecting hump acts as an anchor, aiding the rotational movement of the larva inside the cavity it creates when feeding within its food (Halffter and Matthews 1966). Detailed studies of the biol

Scarab Dung Roller

Rflure 9.6 DUNG SCARABS (SCARABAEIDAE). (a) Perching dung beetle (Eurysternus deplana-tos)- (b) Dung roller (Canthon smaragdulum). (c) Dung digger (Phanaeus demon), male, (d) Dung ^ger, female, (e) Giant dung digger (Coprophanaeus lancifer). (f) Black dung beetle (Dichotomius carolinus).

ogy and taxonomy of the New World dung scarab larvae have been published (Edmonds and Halffter 1972, Halffter and Edmonds 1982).

Dung beetles are well represented in the New World. Dominant are Coprini, especially the genera Dichotomius and Phanaeus, and Scarabaeini, particularly Canthon. Several of the other approximately seventy-five genera are also speciose.

This interesting group has attracted a great deal of attention by collectors and specialists who are rapidly exposing its biology (Halffter and Matthews 1966; Howden and Young 1981; Peck and Forsyth 1982; Peck and Howden 1984; Wolda and Estribi 1985).

References

Edmonds, W. D., and G. Halffter. 1972. A taxonomic and biological study of the immature stages of some New World Scarabaeinae (Coleoptera: Scarabaeidae). Esc. Nac. Cien. Biol., Mexico, An. 19: 85-122. Halffter, G., and W. D. Edmonds. 1982. The nesting behavior of dung beetles (Scarabaeinae), an ecological and evolutive approach. Insto. Ecol. (Mus. Hist. Nat., Mexico City) 10: 1-184. Halffter, G., and E. G. Matthews. 1966. The natural history of dung beetles of the subfamily Scarabaeinae (Coleoptera, Scarabaeidae). Fol. Entomol. Mexicana 12-14: 1-312. Howden, H. F., and V. G. Nealis. 1975. Effects of clearing in a tropical rain forest on the composition of the coprophagous scarab beetle fauna (Coleoptera). Biotropica 7: 77-83. Howden, H. F., and V. G. Nealis. 1978. Observations on height of perching in some tropical dung beetles (Scarabaeidae). Biotropica 10: 43-46.

Howden, H. F., and O. P. Young. 1981. Panamanian Scarabaeinae: Taxonomy, distribution, and habits (Coleoptera, Scarabaeidae). Amer. Entomol. Inst. Contrib. 18(1): 1-204. Navajas, E. 1950. Manifesta^oes de predatismo em Scarabaeidae do Brasil e alguns datos bionomicos de Canthos virens (Mannh.) (Col. Scarabaeidae). Cien. Cult. 2: 284-285. Peck, S. B., and A. Forsyth. 1982. Composition, structure, and competitive behavior in a guild of Ecuadorian rain forest dung beetles

(Coleoptera: Scarabaeidae). Can. J. Zool. 60-1624-1634.

Peck, S. B., and H. F. Howden. 1984. Response of a dung beetle guild to different sizes of dung bait in a Panamanian rain forest Biotropica 16: 235-238. Ratcliffe, B. C. 1980. New species of Coprini (Coleoptera; Scarabaeidae: Scarabaeinae) taken from the pelage of three toed sloths (Bradypus tridactylus L.) (Edentata: Bradypo-diae) in central Amazonia with a brief commentary on scarab-sloth relationships. Cole-op. Bull. 34: 337-350. Wolda, H., and M. Estribí. 1985. Seasonal distribution of the large sloth beetle Uroxys gorgon Arrow (Scarabaeidae; Scarabaeinae) in light traps in Panama. In G. G. Montgomery, ed., The evolution and ecology of armadillos, sloths and vermilinguas. Smithsonian Inst. Washington, D.C. Pp. 319-322. Young, O. P. 1984. Perching of Neotropical dung beetles on leaf surfaces: An example of behavioral thermoregulation? Biotropica 16: 324-327.

Dung Rollers

Scarabaeidae, Scarabaeinae, Scarabaeini, Canthon. Spanish: Ruedacacas (General), escarabajos peloteros (Argentina). Portuguese: Rola-bostas, pilulares (Brazil). Tumble bugs, ball-rolling dung beetles, telocoprids.

These are the well-known dung-ball rollers (fig. 9.6b). The beetle does not dig a burrow prior to forming the ball but pushes the soil away from under the ball after it is made and buries it simultaneously with the digging of the burrow.

The balls may be eaten directly by the adults (food balls), or a single egg may be laid in it and consumed by the larva (brood balls). The ball is always made at the site of the food source before it is rolled. Ball-rolling techniques are highly developed. The usual rolling position for a single beetle is head downward, the forelegs held on the ground and the other legs on the ball. Two beetles may cooperate in rolling, usually one assuming a pushing and the other a pulling position.

Dung Diggers

Scarabaeidae, Scarabaeinae, Coprini, phanaeus. Spanish: Mierderos (Peru). Quechua: Ismatanga (Peru). Burrowing dung beetles, paracoprids.

In this entirely New World genus and its relatives, females first excavate burrows beneath or near the food source. They then extricate a morsel of dung from the main mass and transport it to the underground chamber, sometimes with the aid of a male, carefully model it into a sphere or pear-shaped unit, and provide it with an outer shell of soil and a single egg. Phanaeus do not roll finished balls of dung on the surface of the ground.

These are mostly brightly colored beetles with metallic green, blue, or reddish-purple coppery integuments. Males (fig. 9.6c) have a single, pointed, and erect short to very long head horn and usually also heavy ridges or conical protuberances on a broad prothoracic shield. The latter is steep and somewhat excavated in most. Females lack the horn and ridges (fig. 9.6d). The elytra are strongly grooved. The majority are medium-sized (BL 1.5—2 cm), although the genus Coprophanaeus (subgenus Megaphanaeus) contains some large, bulky species (BL to 5 cm; fig. 9.6e).

See the references under Dung Beetles for natural history of the genus. Reproductive biology is discussed in detail by Halffter and Lopez (1977), and a detailed anatomical and phylogenetic study of the group was made by Edmonds (1972).

References

Edmonds, W. D. 1972. Comparative skeletal morphology, systematics and evolution of the phanaeine dung beetles (Coleoptera: Scarabaeidae). Univ. Kans. Sci. Bull. 49: 731-874.

Halffter, G., and Y. López. 1977. Development of the ovary and mating behavior in Phanaeus. En tomo I. Soc. Amer. Ann. 70: 203-213.

Black Dung Beetle

Scarabaeidae, Scarabaeinae, Coprini, Dichotomius carolinus. Spanish: Rueda caca (Costa Rica).

Adults of this very common dung beetle (Howden 1983) are not ball rollers. They normally divide up cattle and horse droppings into irregular fragments and take them directly into a burrow. The dung may be eaten in this form by adults or packed into a mass at the end of a burrow on which an egg is laid.

These are fairly large beetles (BL 22—30 mm), dull black, and very convex in shape (fig. 9.6f). The elytra bear deep grooves that, toward the posterior, are frequently packed with dry soil from their digging activities. They are nocturnal and often attracted to electric light in lowland areas of Mexico and Central America.

Reference

Howden, H. F. 1983. Dichotomius carolinus colonics (rueda caca, dung beetle). In D. H. Janzen, ed., Costa Rican natural history. Univ. Chicago Press, Chicago. Pp. 713-714.

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