Submitted to: Journal of Insect Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/5/2005
Publication Date: 11/4/2005
Citation: Williams Ill, L.H., Coscaron, M.C., Dellape, P.M., Roane, T.M. 2005. THE SHIELD-BACKED BUG, PACHYCORIS STALLII UHLER (HETEROPTERA: SCUTELLERIDAE) - DESCRIPTION OF IMMATURE STAGES, EFFECT OF MATERNAL CARE ON NYMPHS, AND NOTES ON LIFE HISTORY. Journal of Insect Science. 5:29, Available online: insectscience.org/5.29.
Interpretive Summary: Stink bugs and their relatives are serious pests of many crops, including cotton and soybean, in the United States. Their feeding causes damage to fruit and seeds, leading to significant yield loss. We studied the life history of a stink bug and provided illustrations and written descriptions of its immature stages. The bug completes at least two generations a year, depending on local climatic conditions. Both immature bugs and adults feed on seeds within fruit, killing the seeds in the process. Bugs deposit their eggs on the underside of leaves, and females guard their eggs and immature bugs from predacious insects and spiders. Within the eggs, each embryo is positioned in the same direction toward the ground. This orientation may facilitate aggregation of the immature bugs after they hatch from the eggs. Aggregation of these bugs is important because it increases the likelihood of their survival. The eggs are always oriented upward from the leaf surface. This is the first recorded observation of this phenomenon in stink bugs and their relatives, and may also play an important role in their survival. An experiment demonstrated that care from mothers was extremely important to the survival of immature bugs. When immature bugs were unguarded by mothers they all died in less than 4 days. Our results indicate that pest management strategies that disrupt guarding of immature bugs or their aggregration behavior may reduce crop losses by stink bugs.
Technical Abstract: The life history of Pachycoris stallii Uhler immatures was studied on its host plant, Croton californicus Muell.-Arg. Immature stages of the bug were described and illustrated. Pachycoris stallii is bi- or multivoltine and occurs in xeric areas with sandy soil where. Nymphs and adults feed on seeds within C. californicus fruit. Bugs oviposit on the underside of leaves, and females guard their eggs and first-instar nymphs from natural enemies. Embryonic orientation of prolarvae is nonrandom; each embryo is oriented with its venter directed toward the ground. This orientation may facilitate aggregation of first instars. The longitudinal axes of eggs are always oriented upward at ca. 16° angle of deviation from a line perpendicular to the leaf surface. This is the first recorded observation of this phenomenon in Pentatomoidea. Experimental removal of females guarding first instars results in 100% loss of nymphs, and this is attributed to disruption of the aggregative behavior of nymphs. Maternal guarding appears to be a net benefit to P. stallii, despite possible costs to the brooding female, such as starvation and increased risk from natural enemies.