A Male-Killing Microbe Could Lead to a New Butterfly Subspecies

Male African queen butterflies are facing a tough road ahead, but the cause is something that holds significant interest for science.

The bacteria Spiroplasma is known to infect African queen butterflies throughout their territories in East Africa; however, until now the butterflies have seemed resilient to its gruesome effects: namely, killing male offspring.

In what is described as a “narrow zone” in the Nairobi region of Kenya, the microbe has exploited a chromosomal difference in the African queens there to ensure that female butterflies purge their male offspring.

Researchers from the University of Exeter, who published their findings in the journal “Proceedings of Royal Society of B,” say that the microbial infection even turns sisters against brothers and causes the newly hatched females of the species to eat male eggs.

What’s even more fascinating is that this male-killing microbe fosters the perfect environment for two closely related subspecies of the African queen to diverge.

That’s because the “no males allowed” microbe creates a significant enough area where breeding cannot take place — in effect, an all-female zone. As the microbe continues to impact African queens, it drives a wedge between the two subspecies, which will diverge and become even more distinct.

Study author Dr David Smith explained:

The neo-W [the microbe] effectively acts as a genetic sink for all males, and butterfly populations around Nairobi are nearly all female. Our results demonstrate how a complex interplay between sex, color pattern, male-killing and chromosomes has set up a genetic ‘sink’ that keeps two subspecies apart.

The microbe Spiroplasma isn’t new to science, and while this particular occurrence has led to a rare chance to see divergent evolution in action, the microbe’s ability to turn species against their male offspring is actually well-recorded.

Scientists are interested in this process because it could provide a way of insect population control that could potentially help to control invasive insect species and save native animals and plants.

The pronounced effect seen here doesn’t pose a risk to the overall health of the African queen species, though. Males are still migrating into the females-only zone, so there’s no danger of a population crash.

However, scientists are interested in the idea of proactively infecting certain insect species with particular microbes for other reasons — like reducing the spread of infectious diseases in humans.

The Wolbachia bacteria, for example, plagues certain species of mosquito. When Wolbachia enters a host, it tries to prevent competition from other bacteria or viruses, and it relies on a couple of neat tricks.

Wolbachia hijacks its host’s reproductive cycle, ensuring that successful mating can only occur with other insects who have already been infected by the bacteria. Wolbachia also has the ability to prevent other bacteria and viruses from being picked up by the host.

Scientists believe they may be able to use Wolbachia to significantly cut human infections of the dengue virus and Zika virus.

Proof of concept studies have shown this method to be effective at inhibiting the dengue virus, but more real-world testing will be necessary to understand the broader use of the ingenious technique.

Still, Wolbachia presents the tantalizing possibility of a cost-effective way to beat certain pathogens by simply infecting mosquitoes via tainted food and then releasing them into the wild. In this case, as Wolbachia poses no risk to humans, it should be entirely safe and easy to deploy in the areas it is needed the most.

Who knew that microbes could be so fascinating?

Photo credit: Thinkstock.


John B
John Babout a year ago

Thanks Steve for sharing the interesting info.

william Miller
william Miller1 years ago


Siyus Copetallus
Siyus Copetallus1 years ago

Thank you for sharing.

Marie W.
Marie W1 years ago

Disagree- this kind of action has unintended usually negative consequences.

Quanta Kiran
Quanta Kiran1 years ago


Judith Emerson
Judith Emerson1 years ago

Hope it wrks on the Zika virus mosquitoes!!!!!

Leonard P.
Leonard P1 years ago

While this is a cool discovery, I'm am not too sure that this is a good idea.

Vivianne Mosca-Clark

How many studies have been done to really understand how safe it is?

Karen Ryan
Karen Ryan1 years ago


Liliana Garcia
Liliana Garcia1 years ago

Fascinating is not my preferred adjective for this, maybe puzzling. I don't think this is a good idea. Setting free infected mosquitoes instead of getting rid of them like naturally you have learned to do when they become a nuisance. I think there's something twisted here.