the 1970s, observed in Middle Eastern desert widow spi-
ders something Scott and others have seen in their black
widows, too: One of the pheromones females apply to their
web is so powerful that, upon touching it, males often initi-
ate a full courtship display even when their prospective
partner isn’t there.
It’s been tricky for biologists to figure out which specific
compounds make up the black widow pheromones so
they can tap into those chemical conversations. It was only
through some innovation and some guessing, that Scott,
working with a Simon Fraser University team, figured out
one influential chemical in the pheromone cocktail.
Since some of the pheromones of the redback spider,
a cousin to the black widow, were already known, the
researchers wondered if the species would have any phero-
mones in common. They found that one compound in
particular might overlap between the two.
In a test, they presented male western black widows
with the compound found on the silk of both species
to see if it elicited a response. It worked — the spiders
responded almost as
strongly to the redback
compound as they did to
silk from females of their
own species. This compound
was the first ingredient of
the pheromone cocktail
discovered: a chemical called
N-3-methylbutanoyl-O-
methylpropanoyl-L-serine
methyl ester, or MB-MP-S.
They published their work
in the Journal of Chemical
Ecology in 2015.
Knowing the chemical
recipe for western black
widow pheromones may
have practical applications.
Occasionally, western black
widow spiders end up in
vineyards, alarming workers
or consumers who reach in
for a grape and get a black widow surprise. Once known,
the secrets of spider sexual chemistry could be used to lure
the unwelcome critters into a trap for removal.
Scott continues to be fascinated by exactly what, why and
how western black widows communicate on and off their
webs, navigating what she calls a “sensory storm” of infor-
mation to find one another. It’s just one part of the tangled
black widow mysteries she’s is still trying to unravel. D
Lesley Evans Ogden is a freelance journalist in Vancouver,
British Columbia. Follow her on Twitter: @ljevanso
JULY/AUGUST 2019. DISCOVER 27
A female western black
widow, marked in light blue
by researchers, is courted
by an unmarked male.