Adult heteropteran thoracic endoskeleton (Insecta: Hemiptera): A family-level study

Date of Completion

January 2008

Keywords

Biology, Entomology

Degree

Ph.D.

Abstract

The integument is the outer layer of the insect, comprising the epidermis and the cuticle. Relative shape and degree of development of the integument show extensive variation, associated with body proportion and form. The endoskeleton is a series of cuticular invaginations of the cuticle into the body cavity that provides structural support for trunk and appendicular muscle attachment. ^ This study examines endoskeletal structures in the hemipteran suborder Heteroptera ("true bugs"), to determine their homologies and to learn if there is sufficient variation within the suborder to draw tentative conclusions as to similarities among heteropteran families. The endoskeleton has been described in many arthropod lineages, and the various structures have been termed apodemes, apophyses, fasciae, furcae, phragmata, bridges etc. Much has been written about soft tissue anatomy in Heteroptera, but little notice has been paid to the endoskeleton, especially to the thoracic endoskeleton. Previous authors briefly examined the thoracic endoskeleton of some species, but because of their focus on soft tissue (muscles) there was no detailed analysis of the internal cuticle. Although the heteropteran thorax has long been regarded as taxonomically important and scientists have observed and illustrated the endoskeletal structures the fact that these structures may have morphological and/or phylogenetic relevance seems to have escaped attention. ^ Nomenclature used in previous literature has been somewhat inconsistent. This study on the thoracic endoskeleton and its structures addresses this deficit. Because of the lack of consistency among earlier works, terminology had to be standardized and so a new and consistent morphological nomenclature is provided here. ^ Understanding at what level character variation occurs is important and the suborder Heteroptera, a well studied group, was chosen for this purpose. It is a reasonably well-known group with a well supported phylogeny. The group contains seven infraorders, Enicocephalomorpha, Dipsocoromorpha, Gerromorpha, Nepomorpha, Leptopodomorpha, Cimicomorpha, and Pentatomomorpha or possibly eight including Aradimorpha, 75 families, and approximately 37,000 described species. Species from the orders Hymenoptera and Diptera as well as from the hemipteran suborder Auchenorrhyncha were also examined, to determine if identical or similar structures occur in other insect groups. ^

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