01975nas a2200193   4500008004100000020001400041245010800055210006900163260000800232300001200240490000800252520129500260653002301555100002201578700001601600700001901616700002201635856012401657       2010                        eng d  a0931-204800aInsecticide-induced hormesis in an insecticide-resistant strain of the maize weevil, Sitophilus zeamais0 aInsecticideinduced hormesis in an insecticideresistant strain of  cMar  a142-1480 v1343 aSublethal responses to insecticides are frequently neglected in studies of insecticide resistance, although stimulatory effects associated with low doses of compounds toxic at higher doses, such as insecticides, have been recognized as a general toxicological phenomenon. Evidence for this biphasic dose-response relationship, or hormesis, was recognized as one of the potential causes underlying pest resurgence and secondary pest outbreaks. Hormesis has also potentially important implications for managing insecticide-resistant populations of insect-pest species, but evidence of its occurrence in such context is lacking and fitness parameters are seldom considered in these studies. Here, we reported the stimulatory effect of sublethal doses of the pyrethroid insecticide deltamethrin sprayed on maize grains infested with a pyrethroid-resistant strain of the maize weevil (Sitophilus zeamais) (Coleoptera: Curculionidae). The parameters estimated from the fertility tables of resistant insects exposed to deltamethrin indicated a peak in the net reproductive rate at 0.05 ppm consequently leading to a peak in the intrinsic rate of population growth at this dose. The phenomenon is consistent with insecticide-induced hormesis and its potential management implications are discussed.10aSitophilus zeamais1 aGuedes, N., M. P.1 aTolledo, J.1 aCorrea, A., S.1 aGuedes, R., N. C.  uhttps://weevil.myspecies.info/insecticide-induced-hormesis-insecticide-resistant-strain-maize-weevil-sitophilus-zeamais02603nas a2200193   4500008004100000020001400041245012500055210006900180260000800249300001200257490000800269520189400277653002302171100001902194700001602213700002302229700002202252856013502274       2011                        eng d  a0931-204800aBidirectional selection for body mass and correlated response of pyrethroid resistance and fitness in Sitophilus zeamais0 aBidirectional selection for body mass and correlated response of  cMay  a285-2920 v1353 aResponses to artificial selection on body mass in the maize weevil Sitophilus zeamais (Coleoptera: Curculionidae) were investigated to determine whether changes in body mass are associated with insecticide susceptibility, rate of population growth, and metabolic rate. Two strains of the maize weevil differing in susceptibility to pyrethroid insecticides were subjected to bidirectional selection on body mass. The susceptible strain responded to selection resulting in individuals with lower or higher body mass, but the resistant strain responded significantly only to selection for lower body mass. The resistant strain selected for low body mass increased its level of deltamethrin resistance in 44 x . In contrast, selection for low body mass in the susceptible parental strain led to increased deltamethrin susceptibility (50 x ) and selection for high body mass increased deltamethrin resistance (4 x ). Thus, the correlated response of insecticide resistance to selection for body mass differed between strains, a likely consequence of their distinct genetic background. Regardless, body mass was positively correlated with fitness (reproductive output) (r = 0.79; P < 0.001), while such correlation with respiration rate was significant only at P = 0.07 (r = 0.44). Therefore, the association between body mass and deltamethrin resistance is population-dependent in the maize weevil, and the confluence of deltamethrin resistance and high body mass in a given strain will likely favour its energy metabolism and lead to the mitigation of fitness costs usually associated with insecticide resistance. The genetic background and selection history of insecticide resistant populations should not be neglected since they may favour the confluence of insecticide resistance with mitigation mechanisms of its associated fitness costs limiting the tactics available to their management.10aSitophilus zeamais1 aCorrea, A., S.1 aTolledo, J.1 aPereira, E., J. G.1 aGuedes, R., N. C.  uhttps://weevil.myspecies.info/bidirectional-selection-body-mass-and-correlated-response-pyrethroid-resistance-and-fitness-sitophil