摘要:Semiochemicals are small organic compounds that mediate interactions between
organisms by transmitting chemical messages. They are used by insects for intra- and
inter-species communication in their ecosystem. Mosquitoes transmit malaria, dengue,
West Nile virus, chikungunya, yellow fever, filariasis and encephalitis to human beings
across the globe. Mosquitoes perceive semiochemicals in their environment respectively
emanating from potential hosts and habitats by the sensory apparatus and act wisely for
the benefit of their progeny. Host seeking and/ avoidance, oviposition site seeking
behaviors are governed predominantly by chemical stimuli along with visual cues that
ensure blood feeding and subsequent egg laying to complete the gonotrophic cycle.
Further, plant materials such as neem, tobacco and their infusions are naturally repulsive
to mosquitoes while infusions of Bermuda grass could be a promising avenue for
exploring natural attractant molecules using gas-chromatography coupled massspectrometry
to identify biologically active molecules. In the laboratory studies one
week old infusions of neem seed kernel and dried tobacco leaves reduced 90-97% egg
deposition by gravid females of Anopheles stephensi, Aedes aegypti, and Culex
quinquefasciatus mosquitoes, while oviposition substrates treated with one week old
infusion of Bermuda grass, Cynodan dactylon received 40-60% increased egg laying
compared to control. Through GC-MS analysis of these plant materials revealed several
fatty acids, hydrocarbons, nicotine, thymol, ethyl dithioisoindole, -lactone, -elemene,
squalene, eudesmenol and stigmasterol that could be responsible for the attraction and
repulsion of mosquitoes to respective extracts. Being biological in origin, these
semiochemicals are safe to humans and environment, when judiciously used would
manage effectively the mosquito menace and mosquito borne diseases.