It’s hard to be a bee.
You’re small, you don’t live particularly long, and to make matters even worse, your population is in decline. You’ve got so many things that are hurting you/your environment: viruses, antibiotics, rising temperatures, pesticides, parasites, herbicides, and humans. All of these things pile on one another, and each affects you in different destructive ways creating this “blend of bad” that makes it hard to function, and hard to survive. And us humans rely on that functionality. Quite badly in fact, as bees are the M.V.P. ‘s of the pollinator world, acting as the most important managed pollinators of our sustainable system of agriculture. But, because of all these stressors, we see a 30-40% decrease in those managed bee populations each year.
One of the largest culprits of this decline in recent years has been the “Varroa Destructor”. This well named parasite latches onto bee larva, and eats the bee’s fat reserves. This biting hurts the bee, and can make the poor insect more vulnerable to viruses and harmful bacteria. But! The bees, despite their size, have some ways to fight back. In America, bees have been observed to groom one another, bite the mites and clean up detached mites from the hive. All in the name of mite prevention.
But, not all bees do things the same way. These different methods are more prevalent in different populations of bees. Just like how all humans are individually unique and how there are cultural differences between different groups of humans; different groups of bees display different behavioral “cultures” or norms.
In their study, Smith et al observed one such difference within a specific population of bees. These unique bees were raised out in Indiana by scientists from Purdue University. They were selectively bred by the University to display more mite biting behavior then “normal bees”, as they hoped that these nibbly bees would be more suited to combat the threats of the Varroa Destructor.
Alongside this, the scientists wished to see if mandible shape/size differed between the two differing groups of mites. Mandibles are basically the “teeth” of an insect. Think fangs. Used to protect, and fight, but also used while eating. The bees will use their mandibles to pry the mites off fellow bee bodies, and help get rid of the pest. The mandibles look different from species to species, and vary in ferocity. They can be sharp and pretty scary on some insects, or pretty tame on others. But. Would the extra bitey mites have any differences in mandible shape? Or would the only differences be in behavior?
In order to examine the “bite level” of the bees, the scientists carefully collected mites that had died/fallen to the bottom of the colony and compared the condition of the mite bodies between the two groups of bees. They then checked to see the condition of the mites, and took a number of damaged mites in comparison to total collected. The mites that had been recovered from the “Mite biters” were. Well, they had many bites taken out of them. Chunks gone, limbs missing. While the “normal” bees had some biting, but in comparison. Less ferocious bites, but they still were putting up a fight against the hive invaders.
But did mandibles have anything to do with it? The scientists used some cool new 3-D modeling techniques to get quick, easy, and accurate measurements of the individual bee’s mandibles. They were able to model the mandibles with computer software and look at the differences between the two groups. Turns out there actually was a difference, a sharp one too! The edges of the mandible were shorter for the biters, acting like a knife in their fights against the Varroa mites, able to slice and dice the small pest, and get those mites off the bodies of their fellow bees.
Woof! I certainly wouldn’t want to be a Varroa Destructor any time soon.
Citations:
Smith, Jada, Xaryn L. Cleare, Krispn Given, and Hongmei Li-Byarlay. “Morphological Changes in the Mandibles Accompany the Defensive Behavior of Indiana Mite Biting Honey Bees Against Varroa Destructor.” Frontiers in Ecology and Evolution 9, (2021).
