Sciencists Discover What Prompts Supersedure

Introduction

Red Squirrels

The red squirrels have been entertaining me again this week. Mother squirrel returned to the garden and has been casing the joint and scrambling up onto the ledge above the patio to peer into the sitting room. I hear her claws on the woodwork. A pair of blackbirds come up onto the step every morning and look in at me which is the cue for me to go and feed them, so I wonder if squirrel has a similar sense that I’m a soft touch and she can keep me on my toes too . She and her single offspring now seem to spend a large part of the day in our garden, sometimes almost hidden in the evergreens, and other times leaping through the beech and across the hedge to the acacia above one of bee hives. One of them bounced along the ground underneath the hives the other day.

Assorted nuts appear in the shops around Halloween so I bought some and left hazelnuts on the patio the other day. As I was collecting a varroa tray for counting mite drops, I noticed mother squirrel dancing around only a few feet away from me on the lawn. I stood still and watched for a few seconds before I realised what was happening. The little squirrel was collecting nuts individually from the patio and burying them all over the lawn. I had previously imagined that they dug out one cache and stored piles of nuts together. There’s nothing like observing first hand what goes on in nature.

American Bee Journal

I’m busy reviewing financial outgoings and pruning back where I can as the end of this year approaches and the time for renewing subscriptions comes around.  When it comes to magazine subscriptions the American Bee Journal is my ‘must-have’ journal and I will be keeping up my subs for this, https://americanbeejournal.com/

I always read Dr. Alison McAfee’s articles first and I’m never disappointed. Last month she wrote with a passion about the accidental discovery of what causes queen supersedure. Her excitement and enthusiasm are positively palpable. I love the way she writes for beekeepers explaining complicated scientific things in a lucid and easy-to-understand way. There always seems to be some bit of practical advice for beekeepers from her research which appears to mostly focus on queen bee health.

Viruses and Supercedure

The research under discussion was led by Abigail Chapman who was a Ph.D. student at the time https://doi.org/10.1038/s41598-024-66286-5 , and it focussed on what happens to queens when they are infected with viruses. When the queens were injected with a mixture of black queen cell virus and deformed wing virus B their ovaries shrank and they stopped egg laying. Supersedure cells were found more often in the most heavily infected queens. So, this prompted the scientists to look at the queen’s pheromones for an answer. Most of the queen retinue pheromones, of which there are at least nine compounds, didn’t alter as a result of infection but one did stand out as declining— the oily substance methyl oleate.

Methyl Oleate

McAfee explains that it is not yet known which organ or tissue is responsible for synthesising this substance which is important though not part of queen mandibular pheromone (QMP). The scientists wanted to answer two questions. Firstly, did the decline in methyl oleate arise as direct result of the virus infection, or was the decline the result of shrunken ovaries? McAfee admits that the second question would take a lifetime to fully answer but that by caging healthy queens they were able to compare pheromone profiles of caged and uncaged healthy queens. When you cage a queen and she stops egg laying her ovaries will shrink for the length of time she is caged. They found that the caged queens did indeed have smaller shrunken ovaries and less methyl oleate just like the infected queens, but in the cage study the queens were healthy and not infected. So, the conclusion was that the altered pheromone was probably due to ovary shrinkage and not as a direct consequence of viral infection.
This is so interesting because we now know that when a queen produces enough methyl oleate queen cell building is inhibited and when the levels are low queen cells are built. This is consistent with swarm preparation explains Mc Afee, and why weight loss and egg laying coincides with queen cell rearing before swarming. What is even more interesting, and relevant to beekeepers in queen rearing, is that young larvae and open brood also produce methyl oleate. When beekeepers are grafting larvae and producing queen cells, they usually provide brood frames with ample open brood for a cell building colony but very often some of the grafts are not accepted. McAfee discussed her new findings with queen breeders and they changed strategy and didn’t give cell builders open brood. This resulted in a big increase in accepted grafted queen cells compared with those reared in colonies where frames of open brood were provided. Another change was that the bees started making their own new queen cups on the comb suggesting that methyl oleate also plays a role here too.

This is quite fascinating new information which may help queen breeders and hobbyists be more successful queen producers. 14/11/25.

McAfee, A., (2025) How a Colony Decides to Replace its Queen, American Bee Journal, Volume165 No. 10 October 2025, page 1105.