Exit Strategy: How Pupating Red Mason Bees Deal With “Misorientation” Inside Their Nests

red mason bees

Red mason bees (Osmia bicornis) differ in size by sex, as seen in this pair of male (top) and female (bottom). Such sexual dimorphism means the bees’ methods for correctly orienting themselves in their single-exit nests also vary between male and female. (Photo credit: Justyna Kierat)

By Kelly McKinne

Most people would believe that insects rarely plan how they are going to emerge from their cocoons. From a human perspective, it seems to pale in comparison to the challenges of adulthood for these individuals. That belief could not be further from the truth, as we learn from recent research that was conducted with the red mason bee (Osmia bicornis).

Kelly McKinne

Kelly McKinne

Justyna Kierat of the Institute of Environmental Sciences, at Jagiellonian University in Poland, and her team found that there is incredible planning that occurs with solitary bees and wasps. Kierat says she always believed that the bees planned their emergence from the cocoons, but she was interested in finding out how much planning was occurring and why. Her latest research was published in March in the Journal of Insect Science.

It is known that solitary bees and wasps have interesting nest structures. Kierat says these nests are linear structures, with only one exit leading out. Most individuals will take the initiative to position themselves in cocoons with their head facing the exit. Previous research by Kierat’s colleagues Hajnalka Szentgyörgyi and Michal Woyciechowski found that, like several other insect species, red mason bees occasionally become “misoriented.” This misorientation can be deadly to the insects, as they will continue to chew hopelessly in the wrong direction, even potentially harming nearby siblings.

Although this misorientation can occur in several different species of solitary wasps and bees, the red mason bee can have a misoriented rate as high as 20 percent, compared to most wasps where only 1 percent are misoriented. Kierat chose to study O. bicornis  because she felt that this misoriented rate was incredibly high. If this occurrence was not somehow corrected by the bees, it would cause incredible mortality, which seemed improbable to their survival.

In their study, Kierat and her team wanted to determine if the red mason bees could correct their orientation, based on discoveries made from the “structure of the partition walls” after emerging from the cocoon. Previous research showed that the males were smaller in size than the females and that the males were typically misoriented more often than the females. They predicted that the smaller males would be capable of realizing their mistake and correct themselves after emerging from the cocoon, but the females were too large to correct their direction.

After creating artificial cells and placing bees inside these structures, they recorded subject sex, as well as their individual orientations. Results showed that most males placed incorrectly in the cell were able to determine their orientation based on the “shape and/or texture” of the cell walls and make corrections as they attempted to reach the exit. Females simply chewed forward in the direction they were placed. Previous research showed that females are less likely to be facing the wrong direction, reinforcing the belief that females plan more before cocoon orientation.

Kierat’s study shows us that red mason bees seemingly do an abundance of planning before beginning their adventure into the natural world. More information about this incredible subject can be found in the full study, available at the link below.

Kelly McKinne, MPA, has spent the last several years working and volunteering as a biologist/naturalist in the Midwest and on the east coast. He has served as a local guide for both insect and avian field trips. He currently explores the wilds of Pennsylvania. Twitter: @gonzonaturalist

 

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