GRASSHOPPER SWIMMING AS A FUNCTION OF SEXUAL AND TAXONOMIC DIFFERENCES: EVOLUTIONARY AND ECOLOGICAL IMPLICATIONS

Abstract

Swimming behavior of grasshoppers (21 species from 3 subfamilies) was assessed with respect to sexual and taxonomic differences. The parameters of swimming included capacity (the ability of individuals to reach the edge of a 100 cm diameter pool within 3 min), rate of net displacement (the time required to reach the edge of the pool, if this was greater than 3 min the subject was deemed as incapable of swimming) and orientation (the ability to reach a target of vertical stripes on the pool). Melanoplinae had a significantly greater proportion of individuals capable of swimming than Oedipodinae or Gomphocerinae. Males and females did not differ significantly in swimming capability. Considerable differences were found among species in the rate of net displacement. This rate was significantly greater for Melanoplinae than Oedipodinae, and Oedipodinae were significantly faster than Gomphocerinae. In comparing across all species, females had a significantly greater rate of net displacement than males. Several species exhibited an ability to reach the target at a rate significantly better than chance. However, at the subfamily level, only the Melanoplinae were able to orient to the target at a frequency significantly better than chance. In comparing across all species, the sexes were not found to differ in their ability to orient. Phylogenetic and ecological interpretations of the data are suggested.