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Development of the Hypopharyngeal Glands of Worker Bees (Apis mellifera L.) When Fed Different Protein Sources During the Spring Period
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Department Livestock-Non-Ruminant Animals and Special Industries, Trakia University, Students Campus, 6000 Stara Zagora, Bulgaria
2
Department of Agricultural Machinery, Agrarian and Industrial Faculty, University of Ruse, Angel Kanchev, 7017 Ruse, Bulgaria
*
Author to whom correspondence should be addressed.
Insects 2026, 17(1), 21; https://doi.org/10.3390/insects17010021
Submission received: 6 November 2025
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Revised: 15 December 2025
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Accepted: 21 December 2025
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Published: 23 December 2025
(This article belongs to the Special Issue Biology and Conservation of Honey Bees)
Simple Summary
Honey bees need good protein nutrition in early spring to develop strong nurse bees and raise healthy broods. When natural pollen is scarce, beekeepers use protein supplements, but their effectiveness varies. In this study, we compared six protein sources to see how they affect the development of the hypopharyngeal glands in worker bees. Bee pollen produced the best results, confirming its role as the most complete natural protein. Spirulina showed almost the same effectiveness and appears to be a strong alternative when pollen is limited. Soy isolate and pea protein had moderate positive effects, while brewer’s yeast was the least effective. These results can help beekeepers choose the most suitable protein supplements to support colony development during early spring.
Abstract
The supplementary feeding of bee colonies under conditions of limited natural food sources is essential for maintaining their health and productivity. Pollen is a major source of protein for bees, collected during plant flowering. Its absence negatively affects the secretory activity of the hypopharyngeal glands (HPGs) in young nurse bees. This study aimed to assess the effect of different protein sources provided during the spring period on the development of HPGs in worker bees. An experiment was conducted with 28 bee colonies divided into seven groups of four colonies each—one control and six experimental. The colonies were fed soy isolate (Glycine max), brewer’s yeast (Saccharomyces cerevisiae), spirulina (Arthrospira platensis), pea protein (Pisum sativum), and bee pollen (a mixture of pollens from various plant species). The results confirmed the critical role of pollen, as 40% of bees in the pollen-fed group exhibited HPGs at grade 4. The group supplemented with spirulina showed similar results (35.8%), indicating its potential as an alternative protein source. These findings highlight the importance of proper protein supplementation and suggest that spirulina could serve as a promising substitute for pollen in early spring feeding to support colony development.
Keywords:
honey bee; HPGs; protein sources; supplementary feeding
