Glyphiderus, Westwood 1838:164

Ocampo, Federico C., 2004, Food Relocation Behavior and Synopsis of the Southern South American Genus Glyphoderus Westwood (Scarabaeidae: Scarabaeinae: Eucraniini), The Coleopterists Bulletin 58 (2), pp. 295-305 : 298-301

Glyphiderus, Westwood 1838:164 .

Type species. Anomiopsis sterquilinus Westwood 1837 , here designated.

Description. Form ( Fig. 4 ): Color black; body globose, sides rounded. Size small to medium (length 9.5–22.5 mm; width 6.5–14.5 mm). Head: Surface punctate to densely foveate; form trapezoidal, wider than long. Frons biconcave or slightly convex; Frontoclypeal suture present, complete, with or without small tubercle in middle. Clypeus well developed ( Fig. 4 ) with two medial processes and variable number of denticles; denticles large or small, rounded or acute. Clypeal disc with (males) or without (females) depression in middle. Gena with external margin denticulate or irregularly denticulate. Eyes small, completely divided by gena, halves subequal in size. Antenna 9-segmented. Segment 1 as long as 2–6 combined.Club 3-segmented, elongated, with a distinct glabrous area on external surface of first segment. Pronotum ( Figs. 3–5 ): Transverse, convex; sexual dimorphism present; with 4 horns or tubercles and 1 T-shaped, anterio-medial horn (males) and with deep, wide, longitudinal depression or only with deep, wide, longitudinal depression (females); horns, tubercles, and depression variably developed. Lateral fovea present, rounded or elongated. All margins beaded; lateral margins rounded, densely setose, setae long; posterior margin slightly sinuous. Posterior angle right, with distinct flat area. Elytron ( Fig. 4 ): Globose. Surface with 8 variably impressed striae; with pseudoepipleura well developed at level of 7th elytral stria. Disc with intervals with minute tubercles. Hind wings: Obsolete. Venter: Proepisternum convex, shining, sparsely setose. Prosternum with posterior margin slightly pointed. Mesosternum transverse; mesometasternal suture broadely arcuate, concave in middle. Metasternum length 4.40–4.50 times width at middle. Abdominal sternites 2–6 with sutures distinct; sternite 5 more narrow in middle in males than in females; sternite 6 strongly narrow in middle (males and females). Legs: Mesocoxae subparallel, slightly convergent posteriorly, separated at base ( Fig. 1c ). Protibial dorsal surface punctate to foveate, with dorsomedial fringe of setae; external margin with four teeth; teeth with acute or rounded apex; apical margin oblique, truncate; protibial spur straight or curved at apex. Protarsi absent. Meso and metatibiae slender; with 2 dorsal and 1 ventral fringe of setae, setae arising from base of small denticles; apex expanded, with a fringe of setae on margin. Mesotibia with 2 spurs, medial spur longer than external. Mesotarsus longer than metatarsus. Metatibia with 1 spur. Meso- and metatarsi unequal in size, becoming gracile toward apex, with apex setose. Tarsal claws absent. Male genitalia: Symmetrical, variably sclerotized.

Diagnosis. The following characters will separate Glyphoderus from all other Scarabaeinae in the New World: clypeus with four anterior processes; pronotum with horns, tubercles, or a deep, wide depression ( Figs. 3–5 ); mesocoxae not contiguous at the base ( Fig. 1 ); legs slender; protibia with four teeth; meso- and metatibial apex expanded; protarsi absent; mesotarsus longer than metatarsus; and hind wings obsolete.

Natural History and Food Relocation Behavior. The genus Glyphoderus is restricted the Monte and southeastern Chacoan biogeographic provinces in northeastern Argentina from 268 to 348S latitude and between 150–1,850 m altitude. The climate in these areas is temperate-arid with very little rainfall (between 80–250 mm per year) (Roig-Juñent et al. 2001). The northern and central regions of the Monte province receive rains in the summer, but the south is colder and rainfall is distributed throughout the year ( Morello 1958; Cabrera 1976). The dominant vegetation of this region is a fairly continuous layer of shrubs and grass that, at times, can be very open. The landscape consists of sandy plains, and is characterized by the presence of mountain chains that define several, longitudinal valleys.

The results of behavioral observations and natural history of G. monticola and G. sterquilinus are very similar to those of G. centralis , but are described separately because the first two species observations were carried out by the author whereas the observation of G. centralis was conducted by Zunino et al. (1989).

Under natural conditions, the period of surface activity of G. monticola and G. sterquilinus is from 9:30 am to 1:00 pm, and from 5:00 pm to 7:00 pm, depending on atmospheric and soil temperature. No nocturnal, surface activity was recorded. During the observations atmospheric temperature varied between 21–408C in the shade. Both species prefer open sandy or clay soils with a 20–60% vegetation cover. Glyphoderus sterquilinus and G. monticola , as do most of the Eucraniini , specialize on dehydrated dung pellets. Specimens were observed carrying pellets of ‘‘vizcacha’’ ( Lagostomus maximus (Desmarest)) , ‘‘cuis chico’’ ( Microcavia australis (Geoffroy Saint-Hilaire & D’ Orbigny)) , and goat. Specimens of G. sterquilinus did not take dry horse or cow dung even when it was offered, and they were not attracted to dung traps baited with fresh human or cow dung. When foraging, they run on four legs, keeping their forelegs motionless and in a horizontal position with respect to the surface. Adults run in zig-zags or do not follow any particular direction from their burrow (apparently searching randomly). To carry food, the beetles grasp it with the foretibiae and run forward using only their middle and hind legs ( Fig. 2 ), this behavior is known only for members of the tribe Eucraniini . It is not clear how the beetles find their way back to the burrow. As described by Byrne et al. (2003) and Dacke and Warrant (2002) for the South African flightless dung beetles Scarabaeus rugosus (Hausman) , S. rusticus (Boheman) , Kheper nigroaeneus (Boheman) and Pachylomerus femoralis (Kirby) ( Scarabaeinae : Scarabaeini) Glyphoderus species must rely on cues such as the pattern of polarized light. Beetles may use polarized light as a compass bearing that can be used to ‘‘calculate’’ the direction to the burrow. When the entrance of the burrow is reached, the beetles enter by walking forward rather than backward. Observations published by Zunino et al. (1989) regarding the above behavioral character, suggested that the beetles drop the dung pellet turn back, and enter the nest walking backward dragging the pellet. I have not observed this for any Eucraniini species (see Ocampo 2003). The burrow is always previously dug. It is variable in depth (usually between 0.25–1 m long) and variable in slope (between 35–608 with respect to ground surface). The tunnel may be straight or curved. The depth of the burrow is apparently dictated by the level of soil moisture. Burrows are sometimes bifurcated near the end. The beetles store the food at the end of the burrow and no special chamber seems to be prepared for that purpose. Usually between 3–10 dung pellets are stored, and each pellet is carried independently. Sexual cooperation has been observed and it follows the same behavior as that observed for individuals. No special brood chambers were observed in burrows constructed by pairs. During the hours where there is no surface activity, it is common to observe the entrance of the burrow obscured with sand or the available substrate.

Observations of the food relocation behavior of G. centralis were conducted by Zunino et al. (1989) in La Rioja, Argentina. According to Zunino et al. (1989) this species is mostly active during day between 9:00–11:00 am and sporadically between 4:30–5:30 pm at temperatures between 18–378C. This species occurs in open sandy areas that are mostly devoid of grass cover. Food preferences are almost exclusively dry rodent pellets from: ‘‘vizcacha’’ ( Lagostomus maximus (Desmarest)) , ‘‘mara’’ ( Dolichotis patagonum (Zimmermann)) , ‘‘conejo de palo’’ ( Pediolagus salinicola (Burmiester)) , and rarely dehydrated cow dung.

Figures

Fig. 4. Dorsal habitus of Glyphoderus monticola Burmeister.

Fig. 3. Dorsal view of the pronotum of Glyphoderus centralis Burmeister.

Fig. 5. Dorsal view of the pronotum of Glyphoderus sterquilinus (Westwood).

Fig. 1. Ventral view of metasternum. 1a) Ennearabdus Lansverge; 1b) Eucranium Dejean and; 1c) Anomiopsoides Balckwelder and Glyphoderus Westwood.

Fig. 2. Female of Glyphoderus sterquilinus (Westwood) carrying a rodent dung pellet.