The Web of Life (9) Stimuli


Communication is only successful when the intended message is received. Most receptions straightforwardly match the signal sent. But how a message comes across can be quite different from the intent of the sender. Sometimes it is a case of bait-and-switch, or switch-from-being-bait.

A male jumping spider first attracts the attention of a female not by looks, but how well he moves like food. A male’s best sparking way is to mimic tasty prey. A successful spider’s mating dance is an elaborate display: scraping sounds and buzzes, with an occasional rhythmic thump from the spider’s abdomen slapping the ground. Once a male has cajoled a female to come close, he changes his act: from potential prey to potential mate.

Water mites are ambush predators: they lie in wait with their front legs in the air; a net stance to enhance the chance of grabbing a passing crustacean. As a mating prelude, a male approaches a female while vibrating his legs at 15 Hz: within the range of a crunchy copepod crustacean. A female grabs a vibrating male as she would a prey. The male, larger than any meal, is unhurt. As he starts spewing spermatophores nearby, the female realizes what is going on. She switches to sexual behavior and plucks a spermatophore for insemination.

A male Oriental fruit moth also fools a female by imitating food, but here the signal is scent. A male first finds a female by her scent, but when close by, he wafts his own, which includes a pheromone that is also found in fermented fruit juices, which is the beverage of choice for Oriental fruit moths everywhere.

These examples of preliminary mating signals are communication substitution: signaling in a way that relies upon a strong disposition to pre-existing reception. The first rule of advertising is to get attention.