Investigating a multitrophic interaction involving scale insects, (Stigmacoccus garmilleri; Hemiptera: Margarodidae), oak trees (Quercus spp.), and birds in Veracruz, Mexico

Honeydew, a sugar solution produced as waste by phloem-feeding insects, is a prized food for many species of ants. A honeydew-producing scale insect (Stigmacoccus garmilleri) is associated with oak trees (Quercus spp.) in highland forests of Mexico. Honeydew produced by this species is sufficient to provide nourishment for birds. Birds, particularly Audubon’s Warblers (Dendroica coronata audubonii), aggressively compete for honeydew. Scale insect densities on tree trunks were greatest in pasture trees followed by trees at the forest edge and forest trees. Sugar concentrations of honeydew appeared to be positively correlated with temperature and negatively correlated with relative humidity. Ants involved in interactions with scale insects protect the host plant by reducing the number of herbivorous insects on the host plant. My results suggest that when birds are excluded from feeding on leaf dwelling insects, the tree suffers greater leaf loss similar to findings from ant exclusion studies with scale insects