Optimal ovipositional behaviour of Parthenium beetle, Zygogramma bicolorata Pallister (Coleoptera: Chrysomelidae)

Oviposition is considered as one of the most critical events in the life cycle of phytophagous insects. The preference for a specific site for egg-laying depends not only on food availability and the presence of con­specific tracks, but also on the taxes, colour and curve of the surface of the oviposition site. The ovipositional behaviour of Zygogramma bicolorata Pallister in terms of geo- and phototaxis, colour and texture of substrates was examined. Negatively geotactic substrates were preferred by the insect for oviposition. However, there was no apparent preference for positively or negatively phototactic substrates. Studies on combination of taxes served to reinforce the results of taxes studied singly that the negatively geotactic response was most prominent. Female Z. bicolorta preferred green and plastic over the other colours and textures tested