Attracants can trigger the trail-following and aggregation behaviors of termites. When combined with pesticides, attracants can lure and kill termites, increasing the termite control efficiency. Our previous studies showed that phenol and its derivatives had trail-following activity for the Formosan subterranean termite, Coptotermes formosanus. However, these chemicals are non-polar chemicals that are volatile and insoluble in water, which limited their application in termite control. We hypothesized that the polar molecule, sodium phenoxide, could also trigger the trail-following and aggregation behaviors of C. formosanus, and attracted termites when combined with imidacloprid. Y-path tests showed that the trails treated with sodium phenoxide (0.1 μg/cm, 1 μg/cm, 10 μg/cm) had trail-following activity for C. formosanus. In contrast, sodium phenoxide with low (0.01 μg/cm) or high (100 μg/cm) concentrations could not cause the trail-following behavior. In addition, different castes (worker, soldier and nymph) of C. formosanus showed similar trail-following behaviors responding to sodium phenoxide (10 μg/cm) treated trail, and there was no significant difference in the crawling distance along the sodium phenoxide line. Aggregation-choice tests showed that sand blocks treated with sodium phenoxide (1 μg/g, 10 μg/g, 100 μg/g, and 1000 μg/g) could cause the aggregation preference of C. formosanus. In addition, 1000 μg/g sodium phenoxide significantly decreased survival rate of termite. The number of C. formosanus gathered on sand treated with imidacloprid (50 μg/g) was lower than that of untreated sand significantly. However, the combination of sodium phenoxide (1 μg/g) and imidacloprid (50 μg/g) still triggered the aggregation preference, indicating that sodium phenoxide demised the repelling effect of imidacloprid. Our study provides a theoretical basis for developing insecticide formulations that attract termites.

The Formosan subterranean termite, Coptotermes formosanus, is a wood-feeding pest widely distributed in subtropical and temperate regions of the world, mainly damaging various wooden structures and trees. Due to the massive economic losses and damage caused by C. formosanus, it has drawn significant academic attention in recent years. The understanding of C. formosanus biology is the basis for developing control methods. Here, we systematically reviewed papers about C. formosanus biology published since 2000. The global distribution of C. formosanus is caused by multiple introductions from East Asia and the bridgehead effect, and its suitable distribution range may expand due to global climate changes. C. formosanus behaviors such as foraging, tunneling, and trophallaxis closely associated with chemical control methods (i.e., baiting and chemical barrier) have been intensively researched. In addition, a series of semiochemicals with trail-following, aggregating, tunneling, and feeding-stimulant activities have been successfully identified and screened, providing new insights to lure and kill C. formosanus. Due to the immune response and behavioral resistance of C. formosanus against entomopathogens, the research on biological control of this termite has been stalled. However, technologies such as RNA interference are expected to suppress the disease resistance of C. formosanus and may bring new control technologies. In addition, C. formosanus has complex interactions with environmental microorganisms such as wood-decaying, blue-staining, and Trichoderma fungi, as well as gut microorganisms such as protozoan flagellates, bacteria, archaea, and viruses. C. formosanus has two independent but complementary cellulose degradation systems - the endogenous cellulose degradation system composed of cellulase produced by termites and the exogenous cellulose degradation system composed of symbiotic microorganisms. Its ability to efficiently degrade lignocellulose has important implications for biomass energy research.