A sensitive period for larval gustatory learning influences subsequent oviposition choice by the cabbage looper moth

We examined the effects of larval feeding experience with a deterrent plant latex on subsequent adult oviposition behaviour in the cabbage looper moth, Trichoplusia ni. Larvae were exposed to the latex of Hoodia gordonii at 100 ppm in an artificial diet. This plant material strongly deters oviposition in naïve moths in laboratory choice tests. Larvae that were exposed to the latex either for their entire final instar or throughout larval development showed no oviposition deterrence. This effect persisted when larval exposure to H. gordonii latex was suspended for the final 2 days immediately prior to pupation. However, when exposure to latex was suspended for 1 or more days in the beginning of the final instar or for 3 or more days prior to pupation, oviposition behaviour was deterred in subsequent adult moths (i.e. the adults behaved as naïve moths). Our observation that adult oviposition choice can be influenced by a change in diet in the final larval instar indicates the presence of a sensitive period whereby larval feeding memory can be lost or maintained in adulthood.