Phylogeny of the Ensifera (Orthoptera): A Hypothesis Supporting Multiple Origins of Acoustical Signalling, Complex Spermatophores and Maternal Care in Crickets, Katydids, and Weta

Abstract

The orthopteran suborder Ensifera is a group of interest to many biologists because members of several families within this group communicate by sounds. The evolutionary history of singing and other social behaviors of crickets, katydids and weta (Gryllidae, Tettigoniidae and Stenopelmatidae, respectively) are unclear because of different published opinions on the relationships among ensiferan subgroups (Ander 1939, Zeuner 1939, Judd 1948, Ragge1955a, Sharov 1968). These opinions were not based on formal quantitative analyses. I undertook a cladistic analysis of ensiferan families using mainly anatomical characters. The single most parsimonious (shortest-length) tree divides the Ensifera into two clades: the 'tettigonioids' which comprise (((((Tettigoniidae & Haglidae) Stenopelmatidae) Cooloolidae) Gryllacrididae) Rhaphidophoridae), and the 'grylloids' ((Schizodactylidae) (Gryllotalpidae & Gryllidae)) (my parentheses enclose separate clades). I used this phylogeny to construct the most parsimonious hypotheses for the origins of certain social behaviours from those present in the ancestor of extant Ensifera (an insect that used a burrow as a retreat). There were two origins of sound communication using tegminal stridulation and foretibial ears, three to four origins of a complex spermatophore that is eaten by the female and about seven origins of maternal care of eggs and/or nymphs, a trait correlated with loss or reduction in the ovipositor. I review support for the hypothesis of dual origins of tegminal stridulation and tibial ears, complex structures that are usually regarded as homologous within the Ensifera. Crickets, katydids (= long-horned grasshoppers), and weta comprise the Ensifera, one of two suborders of Orthoptera (Table 1). Numerical analyses of orthopteroid insects indicate that the Ensifera is a natural group as taxa in this suborder appear to form a separate clade (monophyletic group) in both cladistic and phe- netic analyses (Blackith and Blackith 1968). The group is usually regarded as phylogenetically quite diverged from the other ortho- pteran suborder, Caelifera, the grasshoppers, locusts, and their