Insect utilize various chemical compounds for defending themselves and communicating with conspecific individuals. In this review, I summarize the defensive and pheromonal roles of pungent (occassionaly pleasant) secretions released by terrestrial true bugs (Heteropteran). Insects also perceive exogenous chemical signals to find food sources and oviposition sites. I also introduce our recent studies about plant odors which elicit foraging behavior of two stink bug species.

Millipedes provides a pair of exocrine defense glands in the body somites and these glands discharge secretory compounds, such as cyanogenics (mandelonitrile, benzoyl cyanide), aromatic compounds (guaiacohl, creosol), hydroquinones, benzoquinones and phenols which are well known as defensive substances. This review presents summary of the secretory defensive compounds based on Chamberlinius hualienensis Wang and Oxidus gracilis belong to polydesmida millipede during outbreak. The initial defensive secretion emitted from the live millipede during reproductive migration has not yet been clarified from all species of the millipedes. We now describe the characteristics of the defensive secretory compounds emitted from the live millipedes and their apoptotic cell death involved in the induction of the caspase activity.

Medusae of Spirocondon saltatrix smell like cucumber because they release (E)-2-nonenal and (E,Z)-2,6-nonadienal. These compounds are theoretically derived from polyunsaturated fatty acids (PUFA) and might have biological functions as defensive molecule and/or chemical signal.

Odor plume is composed of spatially discrete patches of odor molecules, called filaments. Little is, however, known about how animals utilize spatial odor distribution for navigation. The American cockroach, Periplaneta americana, adapted to closed, obstacle-rich environments, is capable of locating a distant odor source with the use of a single antenna. The cockroach has partially overlapping but distinct receptive fields along the antennal flagellum. One receptive field is added for each nymphal molting in which newborn sensilla are emerged in the proximal base of the flagellum. The cockroach is, therefore, capable of detecting plume boundary and filament size by reading combinatory activity of glomerular output neurons corresponding to individual receptive fields.

For six domestic cats, six grades of odor intensity associated with diets of two kinds for body weight management were evaluated by measuring changes in fecal odor intensity. When one food, which contained highly digestible and hydrolyzed proteins and higher amounts of fibers, was consumed, the scores of three of the six cats were remarkably lower than those obtained with the other, which is not known to contain the above-described proteins and contained lower amounts of fibers. Results suggest that the diet composition show the possibility to influence the fecal odor intensity, although the study was done with a small number of cats and so cannot show an assertive result.