24 DISCOVERMAGAZINE.COM
BY LESLEY EVANS OGDEN; PHOTOGRAPHY BY SEAN MCCANN
the males’ built-in GPS, which allows
them to home in on her web.
A mad dash to the advertising female
ensues. Up to 21 males may show up
within a few hours, though around seven
is more typical, explains Scott. A female’s
pheromone scent “provides information
to males — at a distance — like whether
she’s mated before, and whether or not
she’s hungry,” says Scott. Clues about
a female’s hunger are critical because
in this species, the risk of males being
cannibalized by females is, contrary
to popular belief, highest not after sex,
but before.
Once on a lady widow’s web, males
cautiously communicate not only through
their own chemical signals, but through
dance moves. In research published in
2014, Scott’s colleague Samantha Vibert
figured out that a male’s slow “whisper
dance,” in which he vibrates the web’s
strings, is a careful demonstration to his
poorly sighted potential mate that “I’m
here, but I’m not a prey.”
Without that communication, “if a
male enters the web of a hungry female,
Sex on the Beach
Scientists decode the black widow spider’s
language of love.
Along the coastal sand dunes of Vancouver Island, British
Columbia, seduction on the log-strewn beaches can be dan-
gerous. A male can end up as lunch instead of lover if he doesn’t
read a female’s signals correctly.
A male western black widow spider, that is.
Catherine Scott has spent the past several summers trying
to untangle the nuances of courtship communication in these
spiders, which are found across much of western North America.
A doctoral student at the University of Toronto, she works in the
laboratory of behavioral ecologist Maydianne Andrade, who has
spent decades studying these spiders and their relatives. Now,
Scott’s work is revealing some of the secrets of spider sex.
DATING ON THE WEB
The black widow female is a sit-and-wait predator that builds a
messy-stranded cobweb as a trap for crawling and flying insects.
She stays on this web until she’s fully mature. Then she reaches
out for company.
Like so many 21st-century humans looking for love, a female
black widow in the mood puts a want ad on the web. She’ll per-
fume her web’s silk with pheromones, chemicals that attract the
attention of males within smelling distance. This scent stimulates
O
«
A male can
end up
as lunch
instead of
lover if
he doesn’t
read a
female’s
signals
correctly.
NOTES FROM EARTH
Compared with the iconic female western
black widow (Latrodectus hesperus; left), males
are smaller, paler and have distinct markings.