20th International Congress of Arachnology

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DENVER MUSEUM OF NATURE & SCIENCE REPORTS | No. 3, July 2, 2016
Burnaby, BC, V5A 1S6, Canada; 2University of
Toronto Scarborough, 1265 Military Trail, Scarbor-
ough, Ontario, M1C 1A4, Canada
Male adaptations that limit sperm competition include
guarding females, applying mating plugs and chemically
reducing the attractiveness or receptivity of females.
Female web-building spiders often attract males with
silk-borne volatile pheromones. In widow spiders (Latro-
dectus), the courting male often engages in web reduction
behaviour, during which he excises and bundles sections
of the female’s web and wraps them with his own silk.
This widespread behaviour may function in sexual com-
munication (e.g., through dissemination of male sex
pheromone) and/or decreasing the female’s attractiveness.
In a dense population of western black widows, Latro-
dectus hesperus, we ran mate attraction experiments to
test the hypothesis that web reduction and/or male silk
addition decrease web attractiveness. Male-reduced webs
attracted one third as many males as intact webs; webs
with a similar proportion of silk experimentally removed
were as attractive as intact webs. However, the experimen-
tal addition of male silk did not affect web attractiveness.
We conclude that web reduction in black widows limits
male-male competition by reducing the attraction of rival
males to females’ webs. This effect is probably mediated
through targeted excision of pheromone-laden silk by
courting males, possibly in combination with the male’s
silk forming a physical barrier to pheromone emission.
Keywords: chemical communication; courtship behav-
iour; pheromone, Theridiidae
Poster presentation
Effects of boldness on web-decoration
behavior and foraging success
Edward Z. Z. See, Chia-chen Chang, Daiqin Li
Department of Biological Sciences, National University
of Singapore, 14 Science Drive 4, Singapore 117543
Consistent inter-individual difference in behavior has
been documented in many animals, including spiders.
Many orb-web spiders decorate their webs to attract prey
and show considerable variations in the frequency of
web decorations. Yet no study has explored whether and
how personality could explain web-decoration behavior
and thus foraging success in these spiders. Here, we
tested for the presence of boldness in the St. Andrew
cross spider, Argiope catenulata, and its effects on
web-decoration behavior and foraging success. Boldness
was present in A. catenulata juveniles and adults as
well as females and males. In the wild, female boldness
was correlated with how often females decorated their
webs, and a good predictor of females’ foraging success
and growth. Bolder females decorated their webs more
often, intercepted more prey and grew faster. This study
highlights that spider personality should be considered
in future studies of web-decoration behavior.
Keywords: personality, boldness, Argiope , web decora-
tion, foraging success
Student - poster presentation
Expanding far from home: potential geo-
graphic occupancy of the invasive Cyrtophora
citricola(Araneae: Araneidae) in America
*Laura Segura-Hernández1 , Gilbert Barrantes1 , Adrián
García-Rodríguez2
1Biology School, University of Costa Rica, San Pedro
11501-2060, Costa Rica; 2Ecology Department, Uni-
versidade Federal do Rio Grande do Norte, Natal-RN
59078-900, Brazil
Invasive species often have negative effects on colo-
nized ecosystems. Thus, assessing their environmental
requirements is key to identify potential areas for their
establishment and its consequent impacts. In this study we
identify the climatic features that best describe the distri-
bution of the invasive Cyrtophora citricola and evaluate
its invasion risk in America. We used a Maximum Entropy
algorithm to create predicted distributions based on: 1.
native range, and 2. documented invasive range. Then we
tested for niche conservatism by comparing the average
results from Native and Invasive predictions using a Prin-
cipal Component Analysis and a Discriminant Analysis. We
found that the Native Model shares 29.7% of the climatic
20th International Congress of Arachnology