The Taxonomy and Calling Songs of United States Tree Crickets (Orthoptera: Gryllidae: Oecanthinae). I. The Genus Neoxabea and the niveus and varicornis Groups of the Genus Oecanthus1

Abstract

The tree crickets of the United States include Neoxabea bipunctata (De Geer) and 14 species of Oecanthus . The latter are separable into three groups, as follows. (1) the niveus group includes O. niveus (De Geer), formerly known as angustipennis Fitch; O. exclamationis Davis; O. leptogrammus , whose range is from northern South America to southernmost Texas; O. rileyi Baker, a West Coast species formerly regarded as a physiological race of the snowy tree cricket; and O. fultoni , the well-known snowy tree cricket, misidentified for many years as O. niveus . (2) The varicornis group includes O. varicornis Walker, primarily Mexican but ranging into southeastern Texas; O. californicus Saussure, a western species; and O. latipennis Riley, confined to the eastern States. These last two species had not been correctly distinguished previously, and are best separated by characteristics of the stridulatory file. (3) The nigricornis group, which will be treated in a subsequent publication. O. discoloratus Fitch and O. fuscipes Fitch are placed as nomina dubia. The first two groups and their respective species are discussed in terms of nomenclature and synonymy, geographic distribution, habitat relationships, seasonal life history, morphology (including characters of the stridulatory file), and calling song. The calling song is a particularly useful taxonomic character because it is directly involved in the maintenance of reproductive isolation among sympatric species. Factors causing intraspecific variation in calling songs are discussed, and the effect of temperature is stressed. The descriptions of calling songs are based on field notes and the analysis of extensive recordings made in the field and under controlled laboratory conditions. For most species data are adequate to show the effect of temperature upon frequency, pulse rate, and (for chirping species) chirp rate.