Meeting Abstract

19.1  Jan. 5  Variation in Gryllotalpa major burrow mouths: Why bother? HILL, PSM*; SHADLEY, JR; Univ. of Tulsa peggy-hill@utulsa.edu

Most molecricket males in the Orthopteran family Gryllotalpidae produce sexual advertisement songs from constructed burrows in the soil. The surface openings, or mouths, of the burrows vary in number among species for which they have been described from none to six or more, and the burrow mouth and acoustic chamber it leads to have been useful in discriminating among species in the field. However, burrows of only a few of the 91 or so extant species have been described, and no within-species variation has been reported except for the prairie molecricket Gryllotalpa major, where we have found six distinct shapes to the single burrow opening at White Oak Prairie in Oklahoma, USA. Since the burrow mouth acts as the system radiator in molecrickets, an early hypothesis was that population-level variation in call parameters such as dominant frequency and amplitude of the advertisement call might be linked to the shape of the burrow mouth. However, we have been unable to support this hypothesis empirically and continue to seek a functional role for this non-trivial structural variation. The chirping songs males produce are directed toward flying females, who fly above an aggregation of calling males and then swoop down for a second pass closer to the ground before they land near a burrow and enter through the burrow mouth to mate (or not) underground. Nearby males ignore the airborne song but respond to a vibration component that propagates through the soil. We have been interested in how the chirping call, with its harmonic overtones and vibrational component, has evolved in a grassland habitat when most other molecricket songs worldwide are trills, and how all of this is related, if at all, to the variation in the burrow surface opening.