Sensory system of insect is important for their fitness in the environment. Riptortus pedestris (Hemiptera: Alydidae) is a major pest of bean plants and some fruit trees in Korea, Japan, China, and South Asian countries. This study was conducted to investigate morphology and distribution of antennal sensilla of R. pedestris, using scanning electron microscopy. Antennae of R. pedestris was 11 and 9.84 mm in length in male and female, respectively, and consists of four segments; scape, pedicel, flagellum 1 and 2 (F1 and F2). Five types of sensilla (s.) trichodea, four types of s. basiconica, two types of s. chaetica, and one type of s. coeloconica were preliminary identified in both sexes of adult R. pedestris, based on their size, shape, presence of socket and surface structure. Three types of trichoid sensilla, four types of basiconic sensilla, one type of chaetic sensilla and coeloconic sensilla had numerous pores along the surface of the sensilla, suggesting their olfactory function. Eight types of sensilla (3 trichoid, 2 basiconic, a chaetic and a coeloconic) showed a distinct socket structure at the base of each sensillum. Different types of sensilla showed different distribution along the antennal segments. Two types of trichoid sensilla and two types of basiconic sensilla were distributed on scape, pedicel and F1 flagella subsegment. However, the distribution of eight other types of sensilla was limited to one of two flagella subsegments.

Phytophagous insects detect volatile compounds produced by host and non-host plants, using species-specific sets of olfactory receptor neurons (ORNs). To investigate the relationship between the range of host plants and the profile of ORNs, single cell recordings were carried out to identify ORNs and corresponding active compounds in female Uraba lugens (Lepidoptera: Nolidae), an oligophagous eucalypt feeder. Based on the response profiles to 39 plant volatile compounds, 13 classes of sensilla containing 40 classes of ORNs were identified in female U. lugens. More than 95% (163 out of 171) of these sensilla contained 16 classes of ORNs with narrow response spectra, and 62.6% (107 out of 171) 18 classes of ORNs with broad response spectra. Among the specialized ORNs, seven classes of ORNs exhibited high specificity to 1,8-cineole, (±)-citronellal, myrcene, (±)-linalool and (E)-β-caryophyllene, major volatiles produced by eucalypts, while nine other classes of ORNs showed highly specialized responses to green leaf volatiles, germacrene D, (E)-β)-farnesene and geranyl acetate that are not produced by most eucalypts. We hypothesize that female U. lugens can recognize their host plants by detecting key host volatile compounds, using a set of ORNs tuned to host volatiles, and discriminate them from non-host plants using another set of ORNs specialized for non-host volatiles. The ORNs with broad response spectra may enhance the discrimination between host and non-host plants by adding moderately selective sensitivity. Based on our finding, it is suggested that phytophagous insects use the combinational input from both host-specific and non-host specific ORNs for locating their host plants, and the electrophysiological characterization of ORN profiles can be used for predicting the range of host plants in phytophagous insects.

In insects, the sense of smell is a complex and highly sensitive modality, governing essential decisions such as choice of food and oviposition sites. Plants emit substantial amounts of volatile organic compounds (VOCs), and the characteristic scent represents a dynamic communication channel. Understanding this odor-mediated system is critically important in the habitat management and in the largest view of the conservation biological control. Here we suggest that the fitness of the egg parasitoid ,an important biological control agent of the green vegetable bug may be improved through the understanding of chemical communication in the biological control system. Initially, the attractiveness of four flowering plant species, chosen from apanelofplants based on the longevity of the eggparasitoid on these plants, to T. basalis was assessed, which indicated significant behavioral attraction of T. basalis to the buckwheat flowers. Subsequently, and GC-MS analysis were carried out to identify the olfactory-active VOC semanated from buck wheat, demonstrating that the antennalol factory receptor neurons of T. basalis were responsive to some aliphatic acids as well as a few common plant volatiles. In behavioral bioassays using synthetic formulation based on the chemical and electrophysiological analysis, T. basalis exhibited significant behavioral attraction to the synthetic blend at optimum dose. The findings, in a wider perspective, form the basis for further improvement of the use of the companion plants that may increase the insects’ communities’ ability to persist in an environment.

Chemical ecology has been useful in various aspects of biosecurity that requires dynamic multidisciplinary practices. Some techniques and research outcomes have already been incorporated as routine practices in biosecurity, while many others are yet to come. Many pheromones and other semiochemicals have been being used as highly sensitive, species-specific detection and surveillance tools. When different species interact each other, specific volatile chemicals are often produced. Detection of these specific signature volatile compounds can also be used as an early diagnostic tool. Highly sensitive and discriminating olfactory tissues can be used as low-level chemical sensors. Risk analysis is an important component of biosecurity program. The range of host plants may be predictable by using information on ORN response profiles of a given species and on volatile chemical profiles of the candidate plants. In a study using two Cydia species as a model system, we hypothesize that combinational input from two different groups of olfactory receptor neurons (ORNs), antagonist ORNs and agonist ORNs, may play a key role in discriminating host plants from non-host plants. Semiochemicals can be used as delimitation and eradication tools against invading species. For example, mass trapping with pheromone traps, combined with some other means such as sterile insect technique, effectively eradicated the painted apple moth, an invasive species, in New Zealand. A cooperative research program among New Zealand, USA and Australia is currently underway to use semiochemicals to eradicate the light brown apple moth invading California. Chemical ecology in aquatic environment has been poorly understood. Semiochemicals for marine organisms would also be useful to improve marine biosecurity.