Establishmentof an olfactory conditioning assay for two solitary, cavity-nesting bees

Authors: STANLEY-STAHR, CORY - Utah State University; Pitts Singer, Theresa

Submitted to: Journal of Insect Behavior
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/9/2023
Publication Date: 6/23/2023
Citation: Stanley-Stahr, C.A., Pitts Singer, T. 2023. Establishmentof an olfactory conditioning assay for two solitary, cavity-nesting bees. Journal of Insect Behavior. 36:210-221. https://doi.org/10.1007/s10905-023-09822-x.
DOI: https://doi.org/10.1007/s10905-023-09822-x

Interpretive Summary: To order to demonstrate the ability of insects to learn, an effective tool is needed. One such tool is the process called “simple conditioning.” Conditioning uses a natural response, such as a bee extending its “tongue” (= proboscis) when an antenna is touched with sugar solution, and then in training events adding an aroma at the same time as the sugar solution. Once the bee experiences both the sugar solution and the aroma multiple times, the bee “learns” that the aroma alone indicates that a sugar reward will be provided. For honey bees and some bumble bees, scientists can take advantage of the proboscis extension reflex (PER) as a response to an unconditioned stimulus (= sugar solution), but solitary bees do not exhibit a PER readily (if at all) when their antennae are prodded with an offering of sugar solution. However, some managed solitary bees can be kept in the laboratory and will feed from wicks soaked with sugar or honey solution. We sought to create a protocol that demonstrates learning through simple conditioning for two managed solitary bees, the blue orchard bee and the alfalfa leafcutting bee. For them, we provided a small, simple feeder that they naturally fed from by extending the proboscis to sip the sugary reward. In this study, the feeder with sugar solution was paired with a floral odor for certain time periods as part of the bee training experience. We found that both bee species and sexes can learn after the simple conditioning training, and they show this by extending the proboscis towards material that only contains the sugar-associated odor (but not the sugar-solution). The ability to condition solitary bees could support important studies that address questions related to bee preferences for nesting and floral resources and for effects of pesticides or other stressors on learning and memory.

Technical Abstract: To better understand insect learning ability, demonstration of learning through classical conditioning is an effective tool. Conditioning in social bees takes advantage of the proboscis extension reflex (PER) as a response to an unconditioned stimulus, e.g., sucrose solution, but solitary bees do not exhibit a PER readily (if at all) when restrained and prodded with an offering of an unconditioned stimulus, as is done to elicit PER in honey bees. However, some managed solitary bees can be maintained in the laboratory and will feed from wicks soaked with aqueous sugar or honey. We sought to devise a protocol that demonstrates learning through simple conditioning for two managed solitary bees, Osmia lignaria and Megachile rotundata, by exploiting their ability to explore a small, simple feeder and innately extend the proboscis to retrieve a sucrose reward. In this study, the rewarded feeder was paired with a floral odor during conditioning bouts. Newly emerged adult bees began their training on the day of their emergence and were tested on the fourth day. We found that both bee species and sexes demonstrate learning after simple conditioning by extending the proboscis towards material dosed with the reward-associated training odor. The ability to condition solitary bees could support important studies that address questions related to bee preferences for nesting and floral resources and for effects of pesticides or other stressors on learning and memory.