Habituation in Aedes aegypti mosquito larvae is context specific.

Mosquito larvae live in water and perform a stereotyped escape response when a moving object projects its shadow on the water surface, indicating potential risk of predation. Repeated presentations of the shadow induce a decrease in the response as a result of habituation, a form of non-associative learning defined as the progressive and reversible decrease in response to a specific reiterative innocuous stimulus. Nevertheless, habituation can be context specific, which indicates an association between the context and the stimulus. The aim of this work was to study context specificity in habituation in mosquito larvae Aedes aegypti. Larvae were individually placed in Petri dishes positioned over black, white or black-white striped cardboard as background (visual context). Larvae were presented with a shadow produced by a cardboard square (training) over the course of 15 trials. After the 15th trial, the background was changed and the stimulus was presented once again (test). To analyse habituation in different contexts, we developed a series of learning curve models. We performed a Bayesian model selection procedure using those models and the data from the experiments to find which model best described the results. The selected model was a power law learning curve with six parameters (habituation rate; context-specific asymptotic habituation response, with one parameter per context, i.e. 3 parameters in total; response increase; and autocorrelation) describing the whole experimental setup with a generalised r2 of 0.96. According to the model, a single habituation rate would indicate that habituation was independent of the context, whilst asymptotic habituation would be context specific. If the background was changed after training, there was an increase in response in the test, evincing context specificity in habituation.

Honeybees generalize among pollen scents from plants flowering in the same seasonal period.

When honey bees (Apis mellifera) feed on flowers, they extend their proboscis to absorb the nectar, i.e. they perform the proboscis extension response (PER). The presence of pollen and/or nectar can be associated with odors, colors or visual patterns, which allows honey bees to recognize food sources in the environment. Honey bees can associate similar, though different, stimuli with the presence of food; i.e. honey bees discriminate and generalize among stimuli. Here, we evaluated generalization among pollen scents from six different plant species. Experiments were based on the PER conditioning protocol over two phases: (1) conditioning, in which honey bees associated the scent of each pollen type with sucrose, and (2) test, in which honey bees were presented with a novel scent, to evaluate generalization. Generalization was evinced by honey bees extending their proboscis to a novel scent. The level of PER increased over the course of the conditioning phase for all pollen scents. Honey bees generalized pollen from Pyracantha coccinea and from Hypochaeris radicata These two plants have different amounts of protein and are not taxonomically related. We observed that the flowering period influences the olfactory perceptual similarity and we suggest that both pollen types may share volatile compounds that play key roles in perception. Our results highlight the importance of analyzing the implications of the generalization between pollen types of different nutritional quality. Such studies could provide valuable information for beekeepers and agricultural producers, as the generalization of a higher quality pollen can benefit hive development, and increase pollination and honey production.

Effect of Vegetable Oils as Phagostimulants in Adults of Dichroplus vittigerum (Orthoptera: Acrididae).

Several species of grasshoppers are attracted to vegetable oils. These oils have kairomonal properties mainly due to the presence of linolenic and linoleic fatty acids. This study aimed to determine whether the odors of canola, flax, and olive oils are attractive to Dichroplus vittigerum (Blanchard 1851) and if they induce preference and feeding. We conducted three bioassays to determine whether oil modifies attraction and feeding behavior of this grasshopper. We first determined the attraction of the oils using a wind tunnel, secondly evaluated phagostimulation produced by the oils, and finally performed preference tests comparing consumption of Taraxacum officinale (Weber ex F.H.Wigg. 1780, Asterales: Asteraceae) leaves treated with the oils versus control leaves. Even though all of the oils induced attraction, only flax oil acted as a phagostimulant. However, the oils did not determine the preference and did not increase feeding on leaves. We hypothesize that T. officinale leaves are inherently attractive and treatment with oils did not affect feeding on them. Our results provide a starting point to develop baits that can be used to attract and control these harmful insects, presenting flax oil as a potential bait for D. vittigerum since its odor was both attractive and led to increased feeding or phagostimulation. Future studies should test the effect of the oils on other plant species or at varying doses, under field conditions.