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85
DENVER MUSEUM OF NATURE & SCIENCE
REPORTS
|
No. 3, July 2, 2016
20
th
International Congress of Arachnology
et al. 2013 described
Sicarius cariri, S. diadorim, S.
ornatus,
and designated a neotype of
Sicarius tropicus
(Mello-Leitão, 1936). We present a new Colombian
Lox-
osceles
species that we include in the laeta species group
due to the male’s sub-oval palpal bulb, elongated embolus
longer than the bulb’s diameter, swollen palpal tibia at
least two times longer than the tarsus. The female’s blunt
seminal receptacle lacks any globular lobes at the tip. We
provide new records for
L. lutea
and
L. rufipes
, and we
describe the first species of
Sicarius
know from Colombia.
Keywords: Neotropics,
Sicarius
,
Loxosceles
, tropical dry
forest, cave
Oral presentation
How can desert spiders dig their burrows
in dry sand dunes?
Rainer F. Foelix
1
, Ingo Rechenberg
2
1
Neue Kantonsschule Aarau Zelgli, CH-5000 Aarau,
Switzerland;
2
TU Berlin Bionik Ackerstr. 71-76,
D-13355 Berlin, Germany;
r.foelix@gmx.chTwo desert-living spiders, a sparassid (
Cebrennus
) and
a lycosid (
Evippa
), were studied with respect to their
burrow construction. Both spiders face the problem of
how to transport dry sand and how to achieve a stable
vertical tube.
Cebrennus
has many specialized bristles
on palps and chelicerae which together form a carrying
basket. Small balls of sand grains are accumulated below
and then carried to the burrow entrance, where they
are quickly dispersed. The lycosid (
Evippa
) has no such
bristles and shows a different method for carrying sand:
using a few sticky threads from the spinnerets it glues the
loose sand grains together, then grasps them with palps
and legs and carries them to the outside. Both spiders
stabilize the developing tube on the inside by repeatedly
adding silk rings, while digging down. Although both
spiders live in the same environment (desert Erg Chebbi,
Morocco), they use quite different methods to carry sand.
We conclude that this is due to convergent evolution.
Interestingly, certain desert ants also carry sand grains
with specialized bristles on their mouthparts, in a struc-
ture known as a psammophore. However, these ants dig
in moist sand, which easily forms discrete balls; these are
then deposited around the burrow entrance.
Keywords: functional morphology, desert spider, burrow
construction, microscopy, sand transport
Oral presentation
Male mating success, locomotory per-
formance, and metabolic rate in
Argiope
aurantia
Matthias Foellmer
1
, Maria Modanu
2
, Courtney
Mondoux
3
, Maydianne Andrade
4
1
Department of Biology, Adelphi University, Garden
City, NY, USA;
2
Department of Neurobiology and
Behavior, Cornell University, Ithaca, NY, USA;
3
Department of Environmental and Life Sciences,
Trent University, Peterborough, Ontario, Canada;
4
Department of Biological Sciences, University of
Toronto Scarborough, Ontario, Canada
foellmer@adelphi.eduThe relevance of male morphological attributes, such
as body size and relative limb length, for efficiently
locating sexually receptive females and for prevailing
in competition with other males over access to females
has been the focus of much recent research, especially
in species with pronounced female-biased sexual size
dimorphism (SSD). Nevertheless, results have been
inconsistent and a number of studies have failed to find
relationships between morphology and fitness proxies,
such as climbing speed. Here we focus on a so-far
neglected phenotypic attribute, resting metabolic rate
(RMR), and investigate its importance for males in the
contexts of mating and locomotion in the orb-weaver
Argiope auranti
, a species which exhibits extreme
SSD. We performed three experiments: 1) In staged
mating trials, two size-matched males competed to
mate with a female. Males with higher RMR performed
longer courtships, which translated into higher mating
success. 2) In climbing trials, males with higher RMR
achieved higher maximum running speeds on a verti-
cally mounted rod, and RMR was more important than
morphology for explaining running speed. 3) In endur-
ance trials, RMR had no effect on the distance which
males could run continuously, while average speed was