Learning

In many species, the location of the night harborage is spatially separated from other resources such as food and water. In the laboratory and in urban settings, individuals of B. germanica learn the position of their shelter and of stable food sources in relation to visual landmarks; however, olfactory information, which provides more reliable information about the presence of food, can override the visual cues. The insects learned to associate a certain type of food with a specific site, and were "disturbed" (exhibited complex paths) when the association between food type and food position was modified (Durier and Rivault, 2001b). Young nymphs of this species tend to explore smaller areas, cover shorter distances, and remain longer at depleted food sources than older cockroaches, eventually learning that "there is no point in waiting near a depleted patch, as it will not be renewed immediately" (Cloarec and Rivault, 1991). Periplaneta americana is differentially attracted to various dietary nutrients, and learned to associate certain odors with a proteinaceous food source, particularly when they were protein deprived. No such association between odor and carbohydrate could be established (Gadd and Raubenheimer, 2000). Watanabe et al. (2003) demonstrated that P. americana can be classically conditioned to form olfactory memories. The species also begins including novel foods in its diet after nutrient imbalances (Geissler and Rollo, 1987). It is probable that similar associations occur in nature; cockroach species known to have a wide dietary repertoire may both acquire knowledge of food-associated odors and benefit from past experience.

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