Associative learning and memory through metamorphosis inGrapholita molesta(Busck) (Lepidoptera: Tortricidae)

Abstract

Learning of chemical stimuli by insects can occur during the larval or adult life stage, resulting in changes in the imago chemotaxic behaviour. There is little information on learning in Tortricidae, and associative learning through metamorphosis is unknown in this group. Here, we evaluate the influence of olfactory aversive learning in Grapholita molesta (Busck) (Lepidoptera: Tortricidae) during the immature stage and determine if memory persists after metamorphosis. Larvae (10–12 days old) were conditioned to associate the odour of ethyl acetate with pulses of aversive electric shock. Insects were exposed to air, to the ethyl acetate odour, and to shock, in isolation or combination. After conditioning, both larvae and adults were tested in a two-choice olfactometer. Larvae exposed only to air or ethyl acetate increased legibility. Larvae trained with ethyl acetate and shock simultaneously exhibited significant avoidance to ethyl acetate. Avoidance was still present for at least 72 hours after metamorphosis. Thus, G. molesta has the ability to associate an odour to an aversive stimulus precociously, and this association is maintained through metamorphosis and persists into adulthood.

Leddjurs förmåga att känna smärta och uppleva lidande

“…Ytterligare bevis för klassisk inlärning finns för juvenila tvåvingar som exempelvis bananflugelarver, nattfjäril och vecklare (Grapholita molesta). Hos dessa två fjärilsarter kan de associativa minnen som bildades under larvstadiet bestå i vuxen ålder (Aceves-Piña & Quinn, 1979;Khurana et al, 2012;Blackiston et al, 2008;Sant'Ana et al, 2021).…”

Plasticity in Chemical Host Plant Recognition in Herbivorous Insects and Its Implication for Pest Control

“…In another moth species, the European grapevine moth L. botrana , larval odor experience during feeding on different grapevine cultivars led to female oviposition preference for the experienced cultivar, whereas early adult experience during hatching did not induce any preference [ 47 ]. Associative learning of aversive signals, i.e., associating an odor with an electric shock, also persisted trough metamorphosis in the tortricid moth G. molesta [ 48 ]. Another example for odor experience influencing host plant attractivity has been shown in the blue willow beetle, Phratora vulgatissima, a chrysomelid specialist of willows.…”