Reactions of leopard geckos (Eublepharis macularius) to defensive secretion of Graphosoma lineatum (Heteroptera Pentatomidae): an experimental approach

Varietal Resistance and Chemical Ecology of the Rice Stink Bug, Oebalus pugnax, on Rice, Oryza sativa

The rice stink bug, Oebalus pugnax F. (Hemiptera: Pentatomidae), is a key pest of heading rice in the southern United States. Chemical insecticide application is currently the primary method of control of O. pugnax, warranting an improved management program for this species. The potential other management tactics for O. pugnax include eco-friendly measures such as host-plant resistance, silicon application, and the use of semiochemicals. In this study, the feeding preference and performance of O. puganx on cultivated and non-cultivated rice varieties were examined. Choice tests showed that the rice varieties Cheniere and Kaybonnet were most and least preferred by O. pugnax for feeding, respectively. The results of a no-choice experiment showed that the number of nymphs surviving to the adult stage did not differ among rice varieties, although the percent survival was low on the varieties Kaybonnet and Jazzman. Here, we also showed for the first time that silicon application had a significant negative impact on O. pugnax performance, increasing the nymph development time and reducing survival by almost 40% relative to the control. Based on these results, it could be suggested that silicon amendment is a promising management strategy for this pest. Further research is needed to examine whether silicon application also reduces the feeding damage caused by O. puganx. In addition, the chemical compositions of the metathoracic gland and dorsal abdominal gland extracts were also characterized for the first time in this study, and their biological roles and potential use in pest management are discussed.

Analysis of defensive secretion of a milkweed bug Lygaeus equestris by 1D GC-MS and GC×GC-MS: sex differences and host-plant effect

The composition of defensive secretion produced by metathoracic scent glands was analysed in males and females of the milkweed bug Lygaeus equestris (Heteroptera) using gas chromatography with mass spectrometric detection (GC-MS). The bugs were raised either on cardenolide-containing Adonis vernalis or on control sunflower seeds in order to determine whether the possibility to sequester cardenolides from their host plants would affect the composition of defensive scent-gland secretion. Profiles of the composition of defensive secretions of males and females raised on sunflower were closely similar, with predominant presence of (E)-2-octenal, (E)-2-octen-1-ol, decanal and 3-octen-1-ol acetate. The secretion of bugs raised on A. vernalis was more sexually dimorphic, and some chemicals e.g. (E,E)-2,4-hexadienyl acetate and 2-phenylethyl acetate were dominant in males, but absent in females. Compared to bugs from sunflower, the scent-gland secretion of bugs raised on A. vernalis was characterized by lower overall intensity of the peaks obtained for detected chemicals and by absence of some chemicals that have supposedly antipredatory function ((E)-2-hexenal, (E)-4-oxo-hex-2-enal, 2,4-octadienal). The results suggest that there might be a trade-off between the sequestration of defensive chemicals from host plants and their synthesis in metathoracic scent-glands.