| Summary: | The proboscis extension response (PER) assay revealed the responsiveness of three subspecies of the honeybee <i>Apis mellifera</i> [<i>A. m. jemenitica</i> (<i>AMJ</i>), <i>A. m. carnica</i> (<i>AMC</i>), and <i>A. m. ligustica</i> (<i>AML</i>)] to water and different concentrations (0.00001, 0.0001, 0.001, 0.01, 0.1, 0.5, 1.0, and 1.5 M) of three sugars (fructose, glucose, and sucrose) during the summer and fall seasons. The tested bee subspecies showed significantly different PERs to sugar types across the seasons. The water responsiveness of <i>AMJ</i>, a native bee subspecies, was significantly lower than that of <i>AMC</i> and <i>AML</i>, which showed an equally higher water response in both seasons. During the summer season, <i>AMJ</i> and <i>AMC</i> were equally responsive to each sugar type at all tested concentrations. <i>AML</i> was relatively less responsive to glucose at 0.001, 0.001, 0.01, 0.1, 0.5, and 1.0 M than to fructose and sucrose during the summer season. During the fall season, <i>AMJ</i> was equally responsive to glucose and sucrose at all tested concentrations but showed a significantly different response between fructose and sucrose at 0.001, 0.01, 0.1, 0.5, and 1.0 M concentrations. The PER of <i>AMJ</i> to fructose was lower than that of glucose and sucrose. <i>AMC</i> was equally responsive to all tested sugars at all concentrations, and <i>AML</i> showed a differential response between glucose and sucrose at different concentrations during the fall season. The inter-specific species comparisons revealed that all tested subspecies were equally responsive to fructose at all tested concentrations, and <i>AMJ</i> was more responsive to glucose and sucrose than <i>AMC</i> and <i>AML</i> during both seasons. <i>AMC</i> and <i>AML</i> showed no differences in PER to glucose and sucrose in either season. The <i>AMJ, AMC</i>, and <i>AML</i> nectar and pollen foragers showed no significant differences in PER to glucose and sucrose. The <i>AMC</i> nectar foragers were highly responsive to sucrose than pollen foragers at higher sucrose concentrations (0.1, 0.5, 1.0, and 1.5 M). The <i>AML</i> (nectar forager vs. pollen forgers) showed identical PER to sucrose and glucose but a higher response of nectar foragers to high glucose concentrations (0.5, 1.0, and 1.5 M) than pollen foragers. For water responsiveness, <i>AMJ</i> nectar and pollen foragers showed similar PER to water, whereas <i>AMC</i> and <i>AML</i> pollen foragers were significantly more responsive to water than nectar foragers.
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