Thomas Eisner, the Jacob Gould Schurman Professor of Chemical Ecology, talks about acoustical communication among mosquitoes during his July 23 lecture. Charles Harrington/University Photography
Will insects inherit the Earth?
They already have. With more than 200 million insects for every one human being, Thomas Eisner claims "they all but own it now."
In his Summer Sessions lecture, "The Language of Insects," on July 23 in David L. Call Alumni Auditorium, Eisner discussed how insects gained their pre-eminence over humans using acoustical, chemical and visual communication.
Eisner, Cornell's Jacob Gould Schurman Professor of Chemical Ecology and director of the Cornell Institute for Chemical Ecology (CIRCE), is a world authority on animal behavior, ecology and evolution and is one of the founders of chemical ecology, the discipline dealing with the chemical interactions of organisms.
Eisner pointed to the mosquito as an example of acoustical insect communication. Through a "beautifully worked out system," mosquitoes court each other through high-pitched sounds that can be imitated by a tuning fork, he said. Using slides to illustrate, Eisner showed the audience how the feathery structures, or antennae, on the mosquito actually are ears.
"For the males, flying with bushy antennae can be a real drag, so they only become erect when she's in the mood," he said.
The chemical aspect of insect communication is based on pheromones, or "insect perfume," Eisner said. By studying moths in the dark using infrared light, he has found that a female moth calls to the male by pheromones. During copulation, a package of sperm and nutrients that increase egg production is transferred to the female.
Eisner has found, through watching the "close range pillow talk" of these moths that has been caught on camera, that the females have the upper hand in the relationship. Moths are laden with a certain chemical alkaloid for predator protection, according to Eisner, and the female receives that alkaloid in the package, or "nuptial gift," from the male. "The male may seem to be an honest salesman with his package, but the female can check on his honesty," Eisner said.
The biologist also discussed how insects can use internally produced chemicals as weapons to fight off predators. "If an insect stings an enemy, it is telling them, in simplest terms, bug off," he said. Eisner noted that, in the case of certain insects, "it is remarkable that a living system can internally manufacture something like formic acid without destroying itself."
Visual communication also is vital to insects. Eisner discussed camouflaging as a way for insects to protect themselves. For example, the caterpillar actually catches pieces of flower petals and sews them onto itself to dress up like the plant itself as a disguise.
Another aspect to visual communication is illustrated by lightning bugs, or fireflies. Eisner has studied fireflies extensively and found that the mating patterns are a combination of songs, or sound patterns, from the male and flashes of light from the female. One question, Eisner said, was how do the females know which males were of her species in order to mate while they are all in flight? The answer, Eisner explained, is in the time delay between the end of the song and the flash of light, whether it is one-third of a second or one-fourth of a second.
"Some females are firefly femme fatales, however, because they imitate the delay of another species and kill the male for food," he said.
Fireflies also are important for studying anti-viral compounds, heart stimulating drugs and steroids, all of which have come from compounds from lightning bugs.
People often have the wrong attitude about insects, Eisner said. We should always think of them as being proximal to us, or within kissing distance, he said.
"Give some thought to the little things around you waiting to be studied. It costs relatively little, and a youngster may become a future Darwin," he said.