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193
DENVER MUSEUM OF NATURE & SCIENCE
REPORTS
|
No. 3, July 2, 2016
was reversed during the non-crop season. Thus, comple-
mentary utilization of ditches and paddy fields during
different seasons appeared to maintain
Tetragnatha
populations. Both
Tetragnatha
spiders and flying insects
increased in paddy fields under only EFF, when the sur-
rounding forest cover was high. There was a significant
positive correlation between the abundance of flying
insects and the population growth rate of
Tetragnatha
spiders, suggesting the bottom-up effect of flying insects
emerging from paddy fields. We considered that the high
potential productivity in paddy fields, coupled with the
presence of nearby ditches, maintained high abundance
of
Tetragnatha
spiders in paddy-dominated landscapes.
Keywords: agriculture, paddy landscape, natural enemy,
farming practices
Poster presentation
Sternal apodemes in phalangodid harvest-
men (Opiliones)
Darrell Ubick
1
, Facundo Martín Labarque
2
1
California Academy of Sciences, Entomology, San
Francisco, CA, USA;
2
Instituto Butantan, Lab. Esp.
Colecões Zoológicas, São Paulo, SP, Brazil
dubick@calacademy.orgThe sternal apodeme (SA) is a rarely observed endoskel-
etal plate that has been documented only twice; first by
Loman (1903 for the Asian species,
Mermerus beccarii
(Assamiidae)) and more recently by Thaler (1996 for
three European species of
Scotolemon
(Palangodidae)).
Here we record this apodeme in all examined genera of
Nearctic Phalangodidae (
Banksula, Bishopella, Calicina,
Crosbyella, Enigmina, Megacina, Sitalcina, Texella
and
Tularina
), although not the Malagasy phalangodid,
Bunofagea
. The SA was also not found in several other
laniatorid families examined, including representatives
of Insidiatores (Sclerobunidae and Triaenonychidae) and
higher Grassatores (Assamiidae, Gonyleptidae, Podoc-
tidae, Pyramidopidae, Samoidae, and Zalmoxidae). The
SA is a leaf-like plate that extends from the sternum
into the abdominal cavity, where it serves to anchor the
large muscles that insert into trochanter IV. The SA and
associated musculature are found only in males, which
are richly endowed in additional sexually dimorphic
structures. Of these, the most common are processes of the
hind trochanter (TrIV), which range from small tubercles
to short prongs to massive clubs. Similarly variable is the
size of the SA (and consequently the associated muscula-
ture), from the largest observed in
Sitalcina californica
to the smallest in
Banksula grahami
. This variation of
two associated structures suggests a correlation. Do larger
TrIV structures require a larger muscle mass? Preliminary
comparison of SA to TrIV size shows only partial correla-
tion. Species with TrIV modifications do have larger SAs
compared to those with unmodified TrIVs, but species with
the largest SAs do not have the largest TrIV processes. The
presence of moderate-sized SAs in species lacking male
trochanteral modifications (such as species of
Calicina
) is
puzzling and requires an alternate explanation.
Keywords: Opiliones, Phalangodidae, morphology,
endoskeleton, sexual dimorphism
Oral presentation
Comparative mate assessment in wolf
spiders: results from multimodal playback
studies
George W. Uetz
1
, Brent Stoffer
1
, Maddi Lallo
1
, David L. Clark
2
1
University of Cincinnati, Cincinnati Ohio, USA;
2
Alma College, Alma, Michigan, USA
george.uetz@uc.eduAlthough theory predicts that females should exhibit
ordered preferences for size or expression of male qual-
ity-indicating traits, recent work suggests some species
employ comparative rather than absolute evaluation of
mates. We tested comparative assessment of differences
in male quality by female
Schizocosa ocreata
(Hentz)
wolf spiders with unimodal and multimodal video and
vibratory playback choice tests. Females show ordered
directional preferences for expression of male quality
indicator traits (leg tuft size, vibration amplitude) in
both individual sensory modes and multimodal signals,
as quality of either signal mode affects mate choice
outcome. Females exhibited transitivity of preference,
consistently choosing males with higher quality relative
to an alternate choice. Multimodal choice tests showed
20
th
International Congress of Arachnology