About Megacopta punctatissima
Megacopta punctatissima, commonly called the Japanese common stinkbug, is a taxon that was historically treated as a separate species from Megacopta cribraria, also known as the bean plataspid, kudzu bug, globular stink bug, and lablab bug. Phylogenetic research has since found that the two are not actually distinct species, and the name M. punctatissima is specifically applied to Japanese populations of M. cribraria. The populations that are now classified as M. cribraria in the United States are likely descended from a "M. punctatissima" population from Kyushu, Japan. Japanese populations of this species have gut bacteria that allow them to consume crops such as soybean plants. The Japanese population is genetically closest to East Asian continental populations. The two lineages diverged 0.71 million years ago, when the East China Sea land bridge became submerged. The East Asian continental population branched off from the Southeast Asian population 1.34 million years ago. M. cribraria is a shield bug native to India and China, and it is an agricultural pest of lablab beans and other legumes in its native range. While the bug is harmless to houseplants and people, it frequently enters buildings. It is attracted to white surfaces such as house walls or white vehicles, due to the high reflectance of these surfaces that interacts with the bugs' simple eyes. As a defense mechanism, the bug emits a foul-smelling pheromone that also acts as a congregation pheromone. Aside from its unpleasant odor, this liquid causes a burning sensation and sometimes leaves a red welt on bare skin, and the bug releases this offensive odor when touched, squashed, or poked. Like other members of the family Plataspidae, it has an unusual symbiotic relationship with gut bacteria. Before laying eggs, females deposit particles that contain the symbiont; newly hatched nymphs then eat these particles under natural conditions. Experimentally, nymphs deprived of access to this symbiont show slower growth, smaller body sizes, and higher mortality. This insect is hosted by wisteria, green beans, and other legumes. It sucks sap from the stems of soybean plants, which reduces soybean crop yield. However, when it infests kudzu, an invasive plant species, it substantially reduces kudzu growth. In 2011, within the species' invasive range in Georgia, adult M. cribraria had an extremely high aggregation slope when measured using Taylor's Power Law, with the adult slope (b_adults) calculated at 3.27 ± 0.115. In 2011, slopes followed the order b_adults > b_nymphs > b_eggs. By 2012, and continuing at least through 2013, the adult aggregation score was much lower, and the order of slopes reversed to b_eggs > b_nymphs > b_adults.
