If sterol trafficking to the testes is defective, then spermatogenesis would be negatively affected. Lady beetles also demonstrated a statedependent sterolspecific appetite and redressed their sterol deficit by feeding on plant foliage.The proximate forces that create omnivores out of carnivores have long puzzled ecologists, and this elegant study shows that sterols might be a key factor driving omnivory more broadly in insects.Finally, cholesterol obtained through adult nutrition has been shown to impact fitness. A key implication for all of these species is that cholesterol plays an important role in spermatogenesis. The inability of insect herbivores to synthesize sterols, combined with the constraints on their ability to use particular types of sterols and steroids, can be exploited to develop new insect pest control strategies.A sterolbased approach also has the benefit of being target specific.The disruption of biochemical pathways in the conversion of phytosterols into cholesterol in insect herbivorous pests has been heavily studied, and many inhibitors were discovered in the s. These substrates block enzymatic reactions by competing with phytosterols and subsequent metabolites, but the specific mode of action remains unknown, in large part because of a lack of genetic information.However, highthroughput screening and current molecular biology techniques are providing opportunities to identify the genes involved in sterol metabolism and screen for new compounds. For example, these methods helped identify SCP inhibitors with high larvicidal activities in mosquitos and lepidopteran insects. These compounds disrupt the regular exogenous sterol supply for insects and have low cytotoxicity in mammals.Among these, mangostinderived from the tropical fruit mangosteenexhibits a promising future as a new organic pesticide. Moreover, computeraided exploration of proteins related to sterol metabolism can facilitate the design of novel pesticides. Alternatively, it might be possible to modify plant sterol and steroid profiles to control insect herbivore pests. Studies have suggested that it is not necessary to eliminate all phytosterols to generate genotypes that are resistant against insect pests, which is important because a minimum level of typical phytosterol is required for essential physiological functions in plants. Instead, modifying the ratio of sterols or steroids beyond a particular threshold can significantly inhibit insect population growth. Such an approach is environmentally friendly, with minimal effects on the nontarget species. The major pests in any given agricultural system are usually predictable, and their dietary sterol requirement can generally be identified by comparing the insect tissue sterol profile to that of their typical host plant and confirmed using artificial diets.With this information in hand, crop plants can be genetically modified to express sterols that do not meet the requirements of the pest insect.These include short generation time and high fecundity, as well as the fact that they are generally less expensive to feed and maintain.Moreover, both are highly amenable to sophisticated genetic manipulations, which provide more opportunities for exploring sterol nutrition and homeostasis from a functional genomics perspective.However, in our opinion, insects have some unique advantages as a model system in studying sterol biology.First, the nutritional requirements of insects and the underlying molecular basis largely resemble those of vertebrates.