Author
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Cane, James |
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Submitted to: Journal of Insect Physiology
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 9/18/2016 Publication Date: 9/18/2016 Citation: Cane, J.H. 2016. Adult pollen diet essential for egg maturation by a solitary osmia bee. Journal of Insect Physiology. 95:105-109. Interpretive Summary: Unlike their social kin, females of the many thousands of species of solitary, non-social bees are all fertile and reproductive. They characteristically produce very large eggs for their body sizes, which require substantial amounts of yolk proteins and lipids. For some insects, these nutrients are stored as larvae to be used by adults; for others, adult feeding is necessary. In this study, newly emerged, marked females of a native Osmia bee were confined to cages with pollen-bearing or pollen-less sunflowers. All females regularly visited the sunflowers to drink nectar. The oocytes (developing eggs) of those females with pollen access swelled and developed to maturity, but not those of bees lacking dietary pollen. The guts of females with pollen access were often seen filled with a pollen meal. They continued eating pollen daily later during nesting. It is concluded that adult female solitary bees need to eat pollen for reproduction. In agricultural monocultures, this means providing flowering before the main bloom of a crop. Also, over-stocking managed bees so as to deplete daily floral pollen production before females can eat their evening pollen meals will likely hinder their reproduction. Technical Abstract: Reproduction is a nutritionally costly activity for many insects, as their eggs are rich in lipids and proteins. Non-social bees lay especially large eggs. Adult female bees visit flowers to collect pollen and nectar, or sometimes oils, to feed their progeny. For adult bees, benefits of pollen feeding have only been detailed for the honey bee, Apis mellifera. To experimentally address the reproductive necessity of pollen feeding by a non-social bee, Osmia californica (Hymenoptera: Apiformes: Megachilidae), mated female bees were released into large glasshouse cages provided with either a male-fertile sunflower cultivar or a pollen-less one. Females regularly visited and drank nectar from both cultivars. At emergence, all females’ terminal oocytes (next egg to be laid) were small. Oocytes of females confined with the pollen-less sunflowers remained small, despite frequent nectaring and exposure to other floral stimuli. Females confined with the male-fertile sunflowers frequently consumed both nectar and pollen. Within ten days, their basal oocytes swelled to full size, enabling them to lay eggs. Adults of this solitary bee require dietary pollen to reproduce, which should pace the onset and tempo of their reproductive output. |
