by Carl Strang
This week’s literature review post focuses on hearing in insects. The first paper has to do with where hearing originated within the cricket-katydid group.
Stritih N, Čokl A (2012) Mating Behaviour and Vibratory Signalling in Non-Hearing Cave Crickets Reflect Primitive Communication of Ensifera. PLoS ONE 7(10): e47646. doi:10.1371/journal.pone.0047646
They looked at the group of crickets regarded as the most primitive among the living families that include the crickets and katydids. They found that vibratory behavior on tree bark is involved in courtship (the crickets emerge from caves at night), and organs on the legs that are likely homologs of cricket and katydid ears are receptors for these low-frequency vibrations. There are other insect groups today that communicate through vibrations they set up in plants. So, it apparently started with drumming the floor and feeling the vibration through their legs.
Of course, for hearing to be meaningful there has to be a sound production. The crickets and katydids evolved wings that buzz or chirp when rubbed together.
Gu, Jun-Jie, et al. 2012. Wing stridulation in a Jurassic katydid (Insecta, Orthoptera) produced low-pitched musical calls to attract females. Proc. Nat. Acad. Sci. U.S. http://www.pnas.org/content/109/10/3868
Abstract: “Behaviors are challenging to reconstruct for extinct species, particularly the nature and origins of acoustic communication. Here we unravel the song of Archaboilus musicus Gu, Engel and Ren sp. nov., a 165 million year old stridulating katydid. From the exceptionally preserved morphology of its stridulatory apparatus in the forewings and phylogenetic comparison with extant species, we reveal that A. musicus radiated pure-tone (musical) songs using a resonant mechanism tuned at a frequency of 6.4 kHz. Contrary to previous scenarios, musical songs were an early innovation, preceding the broad-bandwidth songs of extant katydids. Providing an accurate insight into paleoacoustic ecology, the low-frequency musical song of A. musicus was well-adapted to communication in the lightly cluttered environment of the mid-Jurassic forest produced by coniferous trees and giant ferns, suggesting that reptilian, amphibian, and mammalian insectivores could have also heard A. musicus‘ song.”
Their results with this Chinese fossil suggest a song comparable in pitch to our common species of “annual” cicadas, but with a pure tone and so, perhaps, similar in sound to a field cricket’s song but a little higher in pitch.
A final paper reported a study of the ear structure of these insects.
Montealegre-Z., Fernando, et al. 2012. Convergent evolution between insect and mammalian audition. Science 338:968-971.
They did a micro-anatomical and functional study of a rainforest katydid’s ears, and found that the external membrane on the leg is connected by a lever system to a fluid-filled chamber where the sensory cells are stimulated. These components within the insect’s leg are analogous to the structures in our ears.