Hemisquilla californiensis is the only species that we have published on that produces a low frequency sound by vibrating its carapace. The vibration is about 30-50 hz and is produced by a pair of muscles that attach to the posterior lateral carapace. I first describe the sound about 20 years ago and recently Sheila Patek and I published a detailed description of the sound and how it is produced. We do not know its function. It seems to be used as a threat, but we also suspect that it may be used in mate attraction and/or courtship. This is why I was trying to get some males and females this spring. No luck.
There are other reports of stomatopods using sound. I published on a "victory" display in Neogonodactylus where the winner of a contest for a cavity strikes the substrate as the loser flees. This is basically a "don't come back" signal. Several squillids have been reported to produce sound by moving their uropods in and out over the telson, but we think this is just incidental sound that the animals make when struggling. There does not appear to be a specific structure that has evolved for producing this stridulation.
I'm working on one other sound producing species right now. Hopefully after a trip to Australia this fall I will have enough data to discuss it.
Roy
