Learning In Host Seeking

Although the studies are few, it is clear that many insects take advantage of experience in their foraging activities and thus improve efficiency of host finding. For example, butterflies learn to land on leaf shapes that resemble their hosts' leaf shapes, making many fewer mistakes with experience, and they learn many visual cues, especially color, when these are coupled with nectar rewards. Grasshoppers have been shown to learn that certain colored backgrounds are associated with the presence of high-quality food, and the time taken to find the food inside colored boxes in laboratory training experiments with Melanoplus sanguinipes was reduced from about 40 min for naive individuals to less than 10 min after a single experience.

Less is known about olfactory learning, but the work so far suggests that it may be more important than visual learning. Grasshoppers in experiments have been trained with different food odors associated with high-protein, low-carbohydrate diets and low-protein, high-carbohydrate diets. They were then fed untreated diets of one or the other type of imbalance until they were relatively deprived of one or the other major nutrient. Then, given a choice, grasshoppers tended to select against the odor that had originally been paired with the unbalanced food. Thus, if they were overfed protein and underfed carbohydrate, they were more likely to avoid the odor that had originally been paired with highprotein food and instead be attracted to the odor that had originally been paired with high-carbohydrate food.

Food aversion learning has been demonstrated in grasshoppers and caterpillars, whereby individuals having a deleterious postingestive experience after eating a certain food thereafter reject it or eat little of it. However, the role of odor and the importance of the associated cues in behaviors prior to contact have not yet been investigated.

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