Mariko Miyagawa, Graduate School of Agriculture, Tamagawa University, Machida, Tokyo, Japan and Jun Nakamura, Honeybee Science Research Center, Tamagawa University, Machida, Tokyo, Japan.
Caste determination of honeybee divides females into queen and worker with distinct caste-specific formation of external characters in natural condition whereas in the artificial rearing morphological intermediates between 2 castes are frequently obtained. The grading criteria (5 grades: from worker to queen) for each of 4 external characters (chaetotaxy of pollen brush, shapes of pollen rakes, basitarsus and mandible) to determine the queenliness were designed according to the previous scanning electron microscopic observations and applied to distinguish intermediate from queen or worker optically. The queenliness score of each individual bee was calculated as the average of grades of 4 characters. Worker and queen larvae collected at different instars were reared with a royal jelly based diet, and various intermediates were obtained. The queenliness of each individual had a tendency to be determined by the rearing conditions or diets during the first half of larval period. However, in many cases, even after the point of caste determination (between 3rd and 4th instars) the rearing condition effected the queenliness of each characters, Especially pollen rakes and mandible were highly sensitive the changes in rearing conditions, and the grades were widely fluctuated between queen and worker, but the developmental synchronies between these 2 characters were not correlated significantly. Under normal colony condition, when larvae were exchanged between queen and worker cells, at 3rd instar both of larvae developed to queens or workers according to the grafted cell environment while worker larvae at 4th instar grafted to queen cells developed to queens or queen-like intermediates in which only pollen rakes did not reach the grade of queen-level. Therefore, the pollen rake was the most sensitive character to the changes of rearing conditions even after the caste determination.
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