UNIVERSITY OF MAURITIUS RESEARCH JOURNAL – Volume 18B – 2012 University of Mauritius, Réduit, Mauritius 250 Study of Herbivore Response to the Presence of Conspecifics and Heterospecifics in an Insect-Host Plant Relationship Paper Accepted on 22 August 2012 Abstract A given guild feeding on the same host plant can face a combination of different forms of competition. Competition between ecological homologues is normally severe, particularly when the species have no possibility of dispersal, as is the case with Liriomyza huidobrensis and L. trifolii. Under such circumstances, there can be interference competition and/or exploitative competition. Competition at the larval stage impacts on larval growth and development and also on adult life cycle parameters such as size, growth, behaviour, fecundity and fertility. However the effects are not the same under conditions of conspecific and heterospecific competition. Laboratory studies on Liriomyza huidobrensis, L. trifolii and their potato host plant, demonstrated that L. trifolii was affected to a greater extent by interspecific competition, while L. huidobrensis was affected to a greater extent by intraspecific competition. Interspecific competition led L. huidobrensis to greater host-mediated resource recognition and utilisation, resulting in higher developmental and reproductive success. This could provide the explanation for the shift in Liriomyza species observed in Mauritius and in many other parts of the world. Keywords: Liriomyza trifolii, L. huidobrensis, Solanum tuberosum, conspecifics, heterospecifics, differential feeding, exploitative competition. S Facknath* Faculty of Agriculture University of Mauritius Réduit Email: sunif@uom.ac.mu