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United States Department of Agriculture

Agricultural Research Service

Research Project: Managing and Conserving Diverse Bee Pollinators for Sustainable Crop Production and Wildland Preservation

Location: Pollinating Insect-biology, Management, Systematics Research

Title: Comparison of the chemical compositions of the cuticle and the Dufour's gland of two solitary bee species from laboratory and field conditions

Author
item Pitts Singer, Theresa
item Hagen, Marcia
item Helm, Bryan
item Highland, Steven
item Buckner, James
item Kemp, William - Bill

Submitted to: Journal of Chemical Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/17/2017
Publication Date: 5/14/2017
Citation: Pitts Singer, T., Hagen, M.M., Helm, B.R., Highland, S., Buckner, J.S., Kemp, W.P. 2017. Comparison of the chemical compositions of the cuticle and the Dufour's gland of two solitary bee species from laboratory and field conditions. Journal of Chemical Ecology. 43(5):451–468.

Interpretive Summary: Species-specific biochemistry, morphology, and function of the Dufour’s glands have been investigated for social bees and some non-social bee families. However, most of the solitary bees examined previously are ground-nesting bees that use Dufour’s gland secretions to line brood chambers. This study examines the chemistry of the cuticle and Dufour’s gland of two cavity-nesting bees managed for crop pollination, Megachile rotundata and Osmia lignaria. The glandular and cuticular lipid compositions were characterized and compared to each other and according to the nesting experience of adult females. Major lipid classes found were hydrocarbons, free fatty acids, and wax esters. Many components were common to both the cuticle and Dufour’s glands of each species, yet they were not identical in number or relative percent composition. Wax esters and fatty acids were more prevalent in M. rotundata Dufour’s glands than on cuticles. Wax esters were more abundant on O. lignaria cuticles than in Dufour’s glands, and fatty acids were more prevalent in glands of field-collected females compared to any other O. lignaria sample types. Cuticles and glands of field bees were chemically distinct from those of young, laboratory-maintained bees. Comparison of percentiles of individual components of cuticular and glandular profiles of the same bee showed that the proportion of some cuticular components are predictive (correlative) of the proportion of the same glandular components, especially for nesting females. Lastly, evidence suggests that the Dufour’s gland is the major source of nest-marking substances of M. rotundata, but evidence for O. lignaria was less conclusive.

Technical Abstract: The biochemistry, morphology, and function of the Dufour’s glands have been investigated for social bees and some non-social bee families. This is a gland associated with the female bee stinger but does not deliver any poison. Most of the solitary bees examined previously are ground-nesting bees that use Dufour’s gland secretions to line nest cells of offspring. This study examines the chemistry of the cuticle (outer surface of insect body) and Dufour’s gland of two cavity-nesting bees managed for crop pollination, Megachile rotundata (alfalfa leafcutting bee) and Osmia lignaria (blue orchard bee). The glandular and cuticular lipid compositions were identified and compared to each other and according to the nesting experience of adult females. Major lipid classes found were hydrocarbons, free fatty acids, and wax esters. Many components were common to both the cuticle and Dufour’s glands of each species, yet they were not identical in number or relative percent composition. Wax esters and fatty acids were more prevalent in leafcutting bee Dufour’s glands than on cuticles. Wax esters were more abundant on blue orchard bee cuticles than in Dufour’s glands, and fatty acids were more prevalent in glands of field-collected females compared to any other blue orchard bee sample types. Due to their particular chemistry, cuticles and glands of field bees were distinguishable from those of young, laboratory-maintained bees. Comparison of chemistry of the same bee showed that the proportion of some cuticular components are predictive (correlative) of the proportion of the same glandular components, especially for nesting females. Lastly, evidence suggests that the Dufour’s gland is the major source of nest-marking substances of alfalfa leafcutting bees, but evidence for blue orchard bee was less conclusive.

Last Modified: 08/21/2017
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