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Comparative morphology of saldidae and Mesoveliidae (Heteroptera) and its bearing on classification Gupta, Ayodhya Prasad

Abstract

On the basis of his study of the female genitalia, Scudder (1959) suggested that in the Heteroptera-Hemiptera, the families Saldidae and Mesoveliidae might be closely related; the present morphological study was undertaken to determine whether a study of other characters also supports their inclusion in a natural group. In these two families, comparison of the head structures revealed that they are quite distinct. The thorax revealed two types: a Saldula type, and a Mesovelia type, and since it is shown that the structure of the thorax is of little taxonomic value in distinguishing the suprafamilial categories, it was considered that the differences between the Saldidae and the Mesoveliidae need not necessarily indicate a fundamental taxonomic difference. In the abdomen, the presence of the clasping organ in the Saldidae completely separates this family from the Mesoveliidae, The present study shows that the Saldidae and the Mesoveliidae are not closely related as might be inferred from comparisons of the female genitalia; they are quite distinct morphologically. The taxonomic position of the two families was also considered. Most authorities believe that the Mesoveliidae are appropriately placed in the Amphibicorisae, and this is supported by the present study. The position of the Saldidae, on the other hand, has heretofore been very uncertain since this family shows some Pentatomomorph features as well as some Cimicomorph features. Two alternatives have been suggested in this thesis regarding the systematic position of the Saldidae. According to the first, the Saldidae may be considered a Cimicomorph which branched off from the main stem of Cimicomorpha, and subsequently developed Pentatomomorph characters - an assumption which presupposes that parallel evolution has occurred. Alternatively, the Saldidae may be considered a branch of the Pentatomomorpha, which arose after the evolution of some Pentatomomorph characters, but before the evolution of the complete Pentatomomorph complex of characters. This latter alternative takes cognisance of the fact that the Pentatomomorph complex of characters evolved gradually and not by a single 'saltation'. It has been concluded, however, that the data available at present are not sufficient to enable one to state which of the two alternatives mentioned above is the correct one, although I am inclined to consider the former as the more plausible. In addition to the foregoing, two general aspects of the morphology of the Heteroptera were considered, namely the interpretation of the head sclerites and the variation in the thoracic structure between apterous and macropterous forms of the two families.

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