Common Name: Largus bug
Scientific Name: Largus succinctus (Linnaeus).
Description: Both families (Largidae and Pyrrhocoridae) of these bugs are similar in appearance and habits. The largus bug, Largus succinctus (Linnaeus) (Largidae), is about 1/2-inch long, elongated oval and flattened, steel blue in color, and have reddish-yellowish markings around margins of the shield behind the head (pronotum) and abdomen. The outer margins of the pronotum are rounded. The cotton stainer, Dysdercus suterellus (Herrick-Schaffer) (Pyrrhocoridae), is very similar in appearance, being about ½ inch long, steel blue flattened oval bodies with the eyes and side margins of the sharp-edged pronotum bright red. Immatures resemble adults but lack fully-developed wings.
Boxelder bugs, Boisea trivittata (Say) (Heteroptera: Rhopalidae) cause similar concerns as do largus bugs during winter months when these bugs seek shelter in homes and other structures. Adult boxelder bugs have diagonal reddish-orange markings across the forewings (at the edge of the corium just before the membranous part of the wing).
The redshouldered bug, Jadera haematoloma, is another pest of shade trees and often enters homes.
Life Cycle: Mated cotton stainer females lay eggs on cotton plants or drop them on the ground near their host plant. Tiny nymphs hatch from eggs in 5 to 8 days and develop through five stages (instars) over 21 to 35 days before becoming adults.
Habitat, Food Source(s), Damage: Nymphs and adults have sucking mouthparts. Although largus bugs are general feeders, sucking juices from a variety of plants such as oak, wax myrtle and other woodland foliage or, occasionally, weeds, they generally cause little injury to plants upon which they feed.
Largus bugs generally cause little injury to plants upon which they feed. However, in the fall nymphs and adults leave their host plants and seek cracks and crevices in which to spend the winter. They can be common around the home during the fall, crawling randomly around the ground. Cotton stainer nymphs (second and third instars) feed together (gregariously) on cotton bolls while that last stage and adults wander freely over the plant. On long-staple cotton varieties, cotton stainers injure developing bolls by puncturing the seeds and causing plant sap to exude from the feeding sites, resulting in yellow-stained lint and poorly developed bolls.
Pest Status: Largus bugs are seed feeders, occasionally a nuisance when in high numbers around the home; cotton stainers, or “red bugs”, occasionally damage long-staple cotton; both are medically harmless.
Literature: Bohmfalk et al. 1982; Borror et al. 1989.