Maternal Aggression and Juvenile Sociality in Hibiscus Harlequin Bugs

Abstract

Hibiscus harlequin bugs (Tectocoris diophthalmus) are Australian jewel bugs known for their maternal care behavior, gregariousness and warning coloration. They feed on plants in the Malvaceae family, although the nymphs will also cannibalize unguarded eggs. Here, I detail observations over 3-year period in Brisbane (QLD), mostly on cultivated Hibiscus and Malvaviscus varieties, to quantify the frequencies at which nymphs and adults occur in groups and the sizes of these groups. I also performed manipulative experiments where I placed individuals together to form groups, or to threaten females guarding a clutch of eggs, and recorded their responses. I observed that harlequin bugs repeatedly colonized a select few individual bushes in sunny locations within the study area. Egg guarding females defended against both conspecific nymphs and adult bugs placed next to the eggs, but rarely responded to the eggs being touched directly with my finger. Nymphs were far more commonly in groups than solitary, and often appeared to aggregate with non-siblings. Further, nymphs inserted into groups mostly remained there. Adults were usually solitary, and typically moved apart if placed together. I suggest that differences in the typical coloration of nymphs (shiny blue) and adults (orange) and possible dual functions as warning and camouflage might explain why nymphs are vastly more social than adult bugs.