The Classroom
The Classroom – April 2023
Q Can laying workers produce female offspring?
I received two questions on this topic. I list both questions before providing my answer.
I am a southern California backyard beekeeper and have been enjoying the hobby for ten years or so. The articles “The Honey Bees in Africa” & “The Cape Bee, an Unusual Pest of European Bee Colonies” in the February 2023 ABJ issue have me dazed and confused.
I have been taught and have read in numerous articles that laying workers are incapable of producing female\queen honey bees. No mating flight = no fertilized eggs. However, the aforementioned articles seem to indicate that this is not correct. Could you please explain and clarify?
Nick Maggiore
California, January
I read with interest the articles in the February issue of ABJ. In particular, there were a couple of references to Cape honey bee laying workers laying fertilized worker eggs and even queen eggs. This confuses me. How are they doing this? The articles did not mention the how (or I missed it). If they lay fertilized eggs, does this mean they are traveling outside the hive to a drone congregation area? Are they mating inside the hive? It is really interesting as well as confusing!
Joel Zinn
Oklahoma, February
A
I love receiving questions about Cape honey bees. They are very interesting bees and I have been fortunate to work with them off/on over the years. In fact, my Ph.D. is from an institution in South Africa (Rhodes University), where the Cape bees are indigenous. While there, I was able to work with Cape honey bees on a regular basis.
The western honey bee (Apis mellifera) has a natural distribution in Europe, Western Asia, and Africa. This is the species of honey bee that was brought to the U.S. in the 1600s. Now, this species of honey bee is represented by multiple subspecies, likely between 25 and 30. One of these subspecies is distributed in the southern/southwestern tip of South Africa. This subspecies is A.m. capensis, the Cape honey bee. This is a unique subspecies because while most Apis mellifera laying workers produce male eggs, Cape honey bee laying workers can produce female eggs. How does this happen?
The process by which honey bees lay unfertilized eggs that result in viable adult insects is called parthenogenesis. Male honey bees are produced this way. They have no fathers. They result from unfertilized eggs. The production of a male from an unfertilized egg is a particular type of parthenogenesis called arrhenotoky, or arrhenotokous parthenogenesis. This is what most beekeepers know about honey bees, i.e., that unfertilized eggs result in male bees.
Well, it is not entirely true that unfertilized eggs always result in male honey bees. It is most appropriate to say that unfertilized eggs usually result in male bees. It is actually possible for unfertilized eggs to result in female bees as well. This type of parthenogenesis is called thelytoky, or thelytokous parthenogenesis. For most honey bees, arrhenotoky is the rule. For Cape honey bees, thelytoky is the rule. As a quick aside, the workers of all A. mellifera subspecies can lay female eggs without mating. Yet, this is uncommon for all subspecies except Cape honey bees.
In the January 2023 issue of the Classroom, I discussed how sex is determined in honey bees. Put succinctly, a sex determination locus (site in the DNA) determines sex in honey bees. When the offspring only has one version (one allele) of this locus, it becomes a male. Drones, being haploid, can only have one version of this locus because they have no fathers. They only get one version, the one they receive from their mother. Female honey bees get two versions (two different alleles — one from their mom and the other from their father), so they are female. Please review the January issue for considerably more detail on this topic. Now, back to parthenogenesis …
Worker honey bees cannot mate so they can only lay unfertilized eggs. Given this, they usually produce male offspring. This is what you and I are accustomed to happening. Cape honey bee workers also cannot mate, yet their eggs result in females. For this to happen, the egg must have two different alleles at the sex locus. Furthermore, this has to happen WITHOUT the egg receiving an allele from a male honey bee. How can this happen? To answer this, remember that the worker, herself, is a diploid female, meaning she must have two different alleles (one from mom and the second from dad) at her sex locus. The production of sex cells (sperm or egg) happens through a process called meiosis. Meiosis is the process of producing haploid cells. Remember that female bees have two copies of each gene, one from mom and a second from dad. Knowing this, you can think about meiosis as the process in which one copy of each gene goes to form one sex cell while the other copy of each gene goes to form another sex cell. Now, both sex cells only have one copy of each gene, making them a haploid egg cell.
There is one step in meiosis in which the two copies of each gene do not split into two different cells. In this step, the second copy of each gene is inactived. This second, inactive half of all gene pairs becomes something called a “polar body.” In Cape honey bee workers, the polar body can “reactivate” and recombine with the other genes in the nucleus. This takes the haploid nucleus (that was created during meiosis) and makes it diploid, given the polar body reanimates and recombines with the DNA in the nucleus. This, now diploid, cell becomes a female! Thus, Cape workers can lay diploid eggs without mating. The resulting offspring are clones of their mothers as they get both copies of each gene from their mom. Amazing! I know that this answer can still be a bit confusing as it is hard to describe this process without pictures and flow charts. However, Google “polar body,” “arrhenotoky,” and “thelytoky” for more information. Honey bees are just cool.
No one knows with certainty why Cape bee laying workers tend to produce females rather than males. This is an area of active research. The typical explanation I hear is that it is very windy in the Cape region during the time of year that queen honey bees would go on their mating flights (swarm season). Thus, many queens could be lost and colonies be hopelessly doomed as a result. In response, the ability to produce female offspring (which could become a worker or a queen) via thelytokous parthenogenesis keeps colonies from being doomed. The answer is waiting to be discovered!
Q European foulbrood
I know you have written about European foulbrood (EFB) many times before, but I do not recall any information pertaining to how long one should isolate that equipment after there was confirmation of EFB? By that, I mean using frames to make nucs, interchanging frames with other equipment or even extracting the honey supers. Also, how long should you keep your bee tools, coat and gloves isolated or sanitized? Any feedback would be much appreciated.
Rich Butera
Ohio, January
A
These are great questions for which there do not appear to be clear answers. If you were asking about American foulbrood (AFB), I would tell you the safest option is to burn everything. As you know, AHB forms spores that can remain in your equipment and reinfect the bees even after the disease seems to be gone (for decades!).
European foulbrood (EFB), on the other hand, does not …
