Franco, J.C., Antunes, R., Lemos, R., Pinto, A., Campos, L., Borges da Silva, E., Branco, M., & Mendel, Z. 2008 Do mealybug males respond to visual cues when approaching pheromone sources?. Proceedings of the XI International Symposium on Scale Insect Studies, Oeiras, Portugal, 24-27 September 2007. ISA Press Lisbon, Portugal 322 pp.

Notes: Mealybug males (Pseudococcidae) are non-feeding insects whose only purpose is to look for virgin females and mate during the few days of their short life. Based on the pattern that has emerged from the few species whose sex pheromone was already identified, e.g. Planococcus citri (Risso) and Planococcus ficus (Signoret), mate location by mealybug mal seems to be mainly dependant on chemical cues, i.e., sex pheromone. However, the fact that mealybug males apparently only fly after exposure to daylight suggests that visual cu may also be involved in short-range attraction to pheromone sources. As in other neococcoid families (e.g., Coccidae, Eriococcidae, Diaspididae), mealybug males typically have a pair of dorsal and ventral simple eyes plus a pair of smaller lateral ocelli. There is a clear la of knowledge about the functional aspects of this bizarre visual system. As far as we know the only study on the ultrastructure of the eyes of a scale insect male was carried out by Duelli (1978), on an undescribed species of Eriococcus. Duelli (1978) reported that the visual system in scale insects is unique in arthropods because the light sensitive structures ot composed of microvilli, but consist of membrane stacks whose configuration is analogous o the stacked plates of vertebrate cones. Based on this study and other observations, Duelli 1985) suggested that the orientation of the eyes in scale insect males is in a horizontal ring Mound the head because the male's body axis is maintained almost vertical during flight. Their main purpose would be to monitor changes in the position of the body axis with regard to horizon. In this paper we discuss the possibility of mealybug males using visual cues when approaching pheromone sources by presenting as a case study data collected on field experiments using colour sticky plates as pheromone traps to investigate the response of male P. citri and P. ficus.