Ant-treehopper mutualism affecting biocontrol of Parthenium hysterophorus by Mexican beetle, Zygogramma bicolorata Pallister

Infestation of a treehopper, Gargara malabarica Ananthasubramanian and Ananthakrishnan (Membracidae, Homoptera) on Parthenium hysterophorus L. and also a myrmicine ant, Lophomyrmex quadrispinosus (Jerdon) (Hymenoptera, Formicidae) tending these treehoppers is reported for the first time. The ant-treehopper association interferes with the biological control of P. hysterophorus by Mexican beetle, Zygogramma bicolorata Pallister (Coleoptera, Chrysomelidae). The Parthenium plants with ants supported significantly lesser number of grubs and adults of Mexican beetle compared to plants without ants. Mean number of Mexican beetle eggs was low on plants with ants, but it was non-significant. Further, the ants were observed to be disturbing the adult Mexican beetles from settling on the Parthenium plants, and this presumably led to the less Mexican beetle population.