Feeding and locomotory functions in relation to body form in five species of ground beetle (Coleoptera: Carabidae)

Abstract

This paper attempts to describe the relationship between habit, body structure and form in five species of ground beetle representing five different tribes. The results support and broaden the basis for currently accepted ideas about the mode of life of Scaritini, Morionini, Licinini, Omophronini and Galeritini. It examines feeding mechanisms, leg structure and body form. In this study two types of feeding method are recognized: fluid or semi‐fluid feeding, as in Scarites subterraneus, and mixed intake feeding. In the second method, food ingested varies from fluid, mush and recognizable arthropod fragments (Morion monilicornis and Omophron labiatum) to mainly fluids or semi‐fluids with some fragments (Diplochila major and Galerita lecontet). All these species show morphological adaptations of their feeding mechanisms indicative of their feeding habits.Pro‐, meso‐ and meta‐femoral and tibial lengths and femoral width measurements have been made and correlated with body lengths; maximum running speeds and maximum horizontal pulling (= pushing) forces have also been made and correlated with body lengths. Galerita lecontei and Omophron labiatum have long femora, whereas those of Diplochila major are somewhat shorter and those of Scarites subterraneus and Morion monilicornis are very short. Scarites subterraneus has relatively narrow femora although there is a trend towards a narrowing of the femora in Morion monilicornis. Only Omophron labiatum has broad femora. Galerita lecontei and Omophron labiatum have long tibiae whereas Scarites subterraneus and Morion monilicornis have very short tibiae. Diplochila major represents the mainstream of carabids, with tibial lengths lying between the two extremes. All five species show morphological adaptations of their locomotory apparatus indicative of their locomotory abilities.In this study Omophron labiarum was found to be particularly fast at high speed running (i.e. sprinting) whereas Scarites subterraneus was found to be relatively slow. Only Scarites subterraneus showed particularly strong pushing abilities whereas Galerita lecontei was found to be weak at pushing. Omophron labiatum, Diplochila major and Morion monilicornis were found to have pushing abilities between the two extremes.Variations in height of the prothorax and hind body, the widths of the hind body, prothorax and metatergum, and the lengths of the metasternum, metatergum and wings are discussed and compared with body lengths in the five species. These various parameters have been displayed in the form of tables, and have been discussed in relation to the various habits of the five species. Certain trends were noted.Only Diplochila major has body proportions similar to those of mainstream cursorial carabids. Galerita lecontei has a shallow, narrow prothorax which may be correlated with its particular hunting habits. Scarites subterraneus has a somewhat cylindrical body form; the hind body is often narrower and flatter and the prothorax flatter than mainstream cursorial carabids. This kind of body form reduces friction and causes less obstruction when burrowing or moving in confined spaces. Morion monilicornis has a similar body form to Scarites. Omophron labiatum is unique in having a very deep, wide prothorax and hind body. Its oval and streamlined body form ideally suits it for its unusual burrowing habits.