Insect pests are significant challenge to rice production, with over 20 species recognized as major insect pests, including some stink bugs (Hemiptera: Pentatomidae). The rice black bug, Scotinophara coarctata (Fabricius), is an invasive insect species firstly reported in southern Thailand, which later spread northward throughout rice-growing regions. Recently, our research team firstly discovered another insect species that has not been reported in Thailand, the white-spotted stink bug, Eysarcoris ventralis (Westwood), that infests rice fields and causes similar damage to that of the rice black bug. However, distinguishing between these two insect pests in the field is challenging due to their similar characters. We, therefore, pursue the differentiation between these two insects using both morphological characters and barcoding of COI genes, including investigation of the population status. The results showed that these insects display some differences in morphological characters. DNA barcoding of the partial COI gene separated them into different clades. The sample of S. coarctata is arranged in the same clade with S. lurida. All of the E. ventralis samples studied were placed in the same clade with the sample from China, indicating that they were related, but separated from other species of the genus Eysarcoris. The outcomes confirmed that these rice stink bugs are separate species and can be distinguished using both morphological examination and DNA barcoding of the COI gene. The analysis suggested a relatively high degree of genetic similarity among geographically diverse populations of Eysarcoris, with some interspecific differences still detectable within the genus.

White-spotted stink bug, Eysarcoris ventralis, rice black bug, Scotinophara coarctata, rice insect pest, COI gene