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Is Feeding Behaviour on Foliage Affected by lab-Rearing on Artificial Diet?

Abstract:

Eastern spruce budworm, Choristoneura fumiferana, larvae were reared on white spruce (Picea glauca) foliage and/or an agar based artificial diet medium for different proportions of their development: fed foliage throughout, fed diet until the 4th instar then foliage for two instars, fed diet until the 6th instar then foliage for 24 h and fed diet only. The insects were then observed feeding on white spruce needles. First, insects reared exclusively on artificial diet exhibited a longer latency to initiate feeding than insects with some prior exposure to foliage. Second, artificial diet-reared insects and those pretreated on foliage for only a few hours had significantly longer meals but lower food consumption than those reared exclusively on foliage or pretreated on foliage for two instars, suggesting that artificial diet-reared insects ingest foliage more slowly during a meal. Third, caterpillars pretreated on foliage for several days, like their diet-reared and short exposure counterparts, had longer intermeal intervals than foliage-reared caterpillars. Finally, subsequent measurements showed that diet-reared budworm have smaller head capsules than foliage-reared insects. These findings show that prior experience influences a folivore’s behaviour on a given food, that insects reared on artificial diet do not develop the same ability to feed on plants as do foliage-reared insects and that different mechanisms of acclimation to a food operate at different time scales.