Biology: images and videos on the
food relocation behavior and natural history of the tribe Eucraniini
are available at http://www-museum.unl.edu/research/
entomology/SBSAAL/Eucraniini/project.html.
The behavior and biology of Anomiopsoides species are similar
to those of the species of the genus Glyphoderus (Ocampo 2004).
Under natural conditions, the period of surface activity of A.
aurita, A. biloba, A. cavifrons, and A. heteroclyta is
from 9:30 to 13:00, and from 17:00 to 19:00, depending on the atmospheric
and soil temperature. No nocturnal, surface activity was recorded for
any species of Anomiopsoides.
All species
studied prefer open, sandy or clay soils with a 20-60% vegetation cover. Anomiopsoides species,
as most of the Eucraniini, have a specialization for dehydrated dung
pellets. Specimens were observed carrying pellets of “cuis chico” (Microcavia
australis (Geoffroy Saint-Hilaire & D’Orbigny)), “cuis” (Galea
musteloides Meyen), and goat. The use of dung pellets of “vizcacha” (Lagostomus
maximus (Desmarest)) by A. heteroclyta was reported by
Zunino et al. (1989).
Specimens of A. biloba and A.
heteroclyta 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. Two species, A. biloba and A. cavifrons, use
plant material as food source. Specimens of A. biloba were
observed carrying small pieces of dry leaves and seeds (unidentified
plant). Two specimens of A. biloba were observed “cutting” small
leaves and seeds (that grow at ground level) using their clypeal processes. For
that purpose, the beetles placed the leaf or seed in between the medial
clypeal processes and pulled out with their head and pronotum.
The
use of plant material as food source by A. biloba and A.
cavifrons was observed occasionally, but plant material does not
constitute the main food source of these species.
Populations
of Anomiopsoides species occur in isolated areas (usually
not larger than 500 m2). Generally, large numbers of individuals of
one or two species live in the same area and are commonly associated
with rodent nests or goats. The occasional use of plant material by A.
biloba and A. cavifrons could be a response to the intra-
and interspecific competition observed in the relatively small area
of foraging. 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 randomly from their burrow (apparently
searching for food). To carry the food, the beetles grasp it with the
foretibiae and run forward using only their middle and hind legs. 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 (along
with the shortest possible route). 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. The
burrow of Anomiopsoides is always previously dug. It is variable
in depth (usually between 0.20-0.80 m long) and variable in slope (between
35-60° with respect to ground surface). The tunnel may be straight
or curved. The depth of the burrow is apparently associated with the
depth where the beetle finds a certain 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 is prepared for it. Between
3-8 dung pellets are usually 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 other substrate.