Two types of grouping behavior, parallel and linear groups, in the large milkweed bug Oncopeltus fasciatus (Dallas) seem to have survival value. Grouped bugs receive mutual benefit from the ability to perceive stimuli from more directions and are usually touching each other. Color pattern and uniformity of direction causes a striking pattern in aposomatic insects. A combination of the shape of the bugs, limited areas for grouping on the plant, and microclimates have influences on the type and shape of aggregations. Aggregation may also be influenced by the substrate, position of the heat or light source, and changing behavioral and physiological stages of the bug.