I’d like to tell you about one of experiments I did during my PhD studies. I worked with the red mason bee (Osmia bicornis), a common solitary bee species. I was particularly interested in topics related to their reproduction. The red mason bees’ nests are linear, with individual cells in a row, which is common to many cavity nesters. Typically, there is only one entrance, and the other end of the nest is blind. The larvae must know the direction to the exit, and they do. Important source of information is the shape of mud partitions separating the individual cells. I pictured this on the cartoon – the nest entrance is to the right, and you can see that the side of the wall which should be chewed by the bee to go out is rough. The other side is smooth and concave. When you open the nest in winter, you can see the cocoons (each of them has a young adult bee inside) most of which are directed with bee’s head towards the exit. So, in the spring all that the bee has to do is to chew the cocoon wall, and then cell wall, all the time moving forward.
But my older colleagues from the lab observed that some cocoons are oriented in the other direction. Those misoriented bees are more often males than females. What happens to such individuals? Do they emerge from the cocoon and go forward, blocking and killing their siblings inside the nest, and eventually dying unable to exit? Or can they find out that they made mistake, and correct it? In order to check it, I prepared “artificial nest cells” which had the real cell walls attached, put the cocoons inside, and checked which way the misoriented bees will emerge.
The results were quite surprising. The majority of misoriented males turned around in the cell after emerging from cocoon, and exited their cells in the right direction. In contrast, most females didn’t turn around and got out the wrong way. Females are typically larger than males in the red mason bee but it was not the difficulty with maneuvering that prevented my females to choose the correct exit. The artificial cells were large enough for them to turn around – I checked.
It looks like the decision about which way to go out of the nest is made at the different moment by each of the sexes. Females position themselves already as larvae spinning their cocoons, and in spring they simply follow the chosen direction. Males are less rigorous in positioning their cocoons but before emergence they check where they should go. It’s quite reasonable strategy, as big females in real nests (in contrast to my artificial cells) can have difficulty with turning around as adults. If they postponed choosing direction for spring, it could turn out that they are not able to turn and are doomed. In contrast, smaller males don’t face such problems, so they can look for the correct exit later.
Here you can read a paper from my experiment.
Non-honey bees 