Agriculture Reference
In-Depth Information
6
Agroecological Networks in Action
Sex and Sweetness
They had us humans right where they wanted us. How often in evolu-
tionary history does one organism convince another to flood their entire
habitat with the smell of sex? To develop a scientific sub-discipline to
investigate it? And to manufacture sex pheromones on an industrial
scale? And on top of that, to convince others to synthesize and release
the sweet scent of pear fruit volatiles? To experience the joy of codling
moth sex pheromones and pear kairomones, the Sacramento River pear
district was the place to be!
Scientists assumed the perspective of males. Through evolutionary
processes, the female codling moth developed the ability to use a species-
specific chemical to attract the male, which in turn had developed
specialized receptor cells in their hair-like antennae to transmit micro-
electric impulses through the nervous system to the insect's brain and
orient it toward the female for sex. Lepidopteran insects so fascinated
scientists that in the 1950s they had developed an electroantennogram to
measure the electrical current passing along the male antenna from the
single sensory receptor, discovering the species-specific stimulus of these
chemicals. So powerful are codling moth sex pheromones that they have
persuaded us humans to stop trying to kill the insect and instead, deploy
techniques to over-stimulate them.
Early laboratory research into insect behavior revealed the degree
to which they as a taxonomic class relied on chemical stimuli for com-
munication, feeding and reproduction. Scientists gave them a name:
semiochemicals. Pheromones are semiochemicals for intra-species com-
munication, or at least that is how some species of insects use them. In
 
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