Field boundaries restrict dispersal of a tropical tiger beetle, Megacephala angustata Chevrolat 1841 (Coleoptera: Cicindelidae)

Abstract

HORGAN FG,CH\uc1VEZ JC. 2004.Field boundaries restrict dispersal of a tropical tiger beetle, Megacephala angustata Chevrolat 1841 (Coleoptera;Cicindelidae). Entomotropica 19(3): 147-152. Field boundaries may divide populations of predatory invertebrates into local populations at the field scale by restricting between-field dispersalThis could reduce recolonisation rates after pesticide use or decrease the efficiency of numerical responses by natural enemies to pest outbreaks.The present study examines the impact of field boundaries on dispersal of the predatory tiger beetle, Megacephala angustata Chevrolat 1841 at a farm in coastal El Salvador. Pitfall trapping indicated that beetles occurred in most habitats on the farm. In pastures, captures were higherin open, unshaded areas than under field boundaries. Beetle dispersal was examined in a capture-mark-recapture study at the site. Movement between fields was very rare as indicated by a linear relationship between the accumulated number of marked beetles and the proportion of recaptures in each of three fields. In spite of frequent recaptures, three weeks after marking, only 2 of 401 beetles were found outside the fields where they had been originally captured and marked.HORGAN FG, CH\uc1VEZ JC. 2004. Barreras vivas como agente de restricci\uf3n para la dispersi\uf3n de un cicind\ue9lido tropical, Megacephala angustata Chevrolat 1841 (Coleoptera: Cicindelidae). Entomotropica 19(3): 147-152. Las barreras vivas pueden restringir la dispersi\uf3n de invertebrados depredadores en tierra agr\uedcola y dividir sus poblaciones en poblaciones locales a nivel de campo con consecuencias tanto para la recolonizaci\uf3n despu\ue9s del uso de plaguicidas como el control natural de plagas. En el estudio presente se investiga el efecto de barreras vivas sobre la dispersi\uf3n de Megacephala angustata Chevrolat 1841 en una granja en la costa de El Salvador.Trampas de ca\uedda indicaron una aversi\uf3n a los habitat sombreados,incluso a la sombra de barreras vivas,por la especie.Un estudio captura-marca-recaptura indic\uf3 que el movimiento entre potreros es poco com\ufan.Tres semanas despu\ue9s de marcar los escarabajos y a pesar de frecuentes recapturas, solamente 2 de 401 individuos se encontraron afuera de los potreros donde se les hab\uedan marcado