Insect Vibrational Communication

I’ve always been interested in animal communication. When I was very young I was convinced if I learned all the nuances of feline communication I would be able to talk to my cat. While this never came to fruition, the fascination of understanding animal communication remained. As an undergraduate I started studying bird behavior and communication and suddenly the birds in the trees transformed from pretty background noise to complex territorial wars, desperate love ballads, and cries for help. I was hooked. A guest speaker from LSU came to my university and gave a talk on vibrational communication in insects and I was blown away at the idea of an entire world of communication we are never privy to. When the opportunity to study insect communication for my master of science presented itself, I took it.

I set up my recording lab in an old creaky building in the entomology department. I put together a marble table with sand filled legs to dampen any ambient noise (which worked great except for during earthquakes). I bought a piezoelectric accelerometer that attached to plant stems with a ball of wax. As the insects sends out its vibrations, the accelerometer picks it up from the plant and transforms it into an electrical signal. This signal then travels to the signal amplifier and is amplified into a sound we can actually hear and analyze. This sound was captured and recorded using the program Adobe Audition.

Insect recording setup

I used two different populations of blue-green sharpshooters for the recordings: one from far northern California, and one from Laguna Beach (a southern CA location). I wanted to see if the large geographical separation had any impact on their vibrational calls. Twelve hundred recording hours later, I had my answer. Although both populations gave the same types of calls, their average frequencies were different and they gave very different amounts these calls. The southern populations were much more vocal, calling more often than their northern counterparts, and these northern males had a higher pitch than ones down south.

Interesting, but I also wanted to know if these differences have any impact on mating. I stuck a female and male together from the different populations and measured reproductive success. The cross-breeding between different populations had a much lower reproductive success (as low as 7% success) compared to the same populations (almost 50% breeding success). Could these differences be indicative of incipient speciation? I would love to see if these differences get more extreme as populations are further separated. How would a population from Canada compare to one from Nicaragua?

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