Feeding and locomotory functions in relation to body form in five species of ground beetle (Coleoptera: Carabidae)
Authors: Forsythe Trevor G. 
Published: March 2009

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 inScarites subterraneus, and mixed intake feeding. In the second method, food ingested varies from fluid, mush and recognizable arthropod fragments (Morion monilicornisandOmophron labiatum)to mainly fluids or semi‐fluids with some fragments (Diplochila majorandGalerita 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 leconteiandOmophron labiatumhave long femora, whereas those ofDiplochila majorare somewhat shorter and those ofScarites subterraneusandMorion monilicornisare very short.Scarites subterraneushas relatively narrow femora although there is a trend towards a narrowing of the femora inMorion monilicornis.OnlyOmophron labiatumhas broad femora.

Galerita leconteiandOmophron labiatumhave long tibiae whereasScarites subterraneusandMorion monilicornishave very short tibiae.Diplochila majorrepresents 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 studyOmophron labiarumwas found to be particularly fast at high speed running (i.e. sprinting) whereasScarites subterraneuswas found to be relatively slow. OnlyScarites subterraneusshowed particularly strong pushing abilities whereasGalerita leconteiwas found to be weak at pushing.Omophron labiatum, Diplochila majorandMorion monilicorniswere 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.

OnlyDiplochila majorhas body proportions similar to those of mainstream cursorial carabids.Galerita leconteihas a shallow, narrow prothorax which may be correlated with its particular hunting habits.Scarites subterraneushas 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 monilicornishas a similar body form toScarites. Omophron labiatumis 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.