Male Mosquitoes Are Bloodthirsty Too, Under the Right Conditions

It’s long been believed that only “female mosquitoes” bite and drink blood, while “male mosquitoes” stick to sipping on nectar. However, new research is turning that idea on its head, showing that under certain conditions, “male mosquitoes” may also develop a taste for blood.

This discovery could change our understanding of “mosquito behavior” and even hint that males might play a minor, previously overlooked role in “disease transmission”.

Males in Search of Blood: When Sugar and Humidity Are Scarce

The surprising finding emerged when researchers observed “male Culex tarsalis” and “Aedes aegypti” mosquitoes in the lab. While these males typically avoid blood, it turns out they may change their habits when they’re “dehydrated” and can’t find sugar.

In a study published as a preprint on “October 8” in ‘bioRxiv.org‘, scientists at Penn State University found that male mosquitoes’, deprived of their usual nectar meals and exposed to low humidity, were willing to feed on blood through an artificial membrane.

The study’s lead, Jason Rasgon, an entomologist, conducted an unusual experiment to further test this behavior. He placed his hand inside a cage filled with male mosquitoes. Under normal circumstances, the males showed little interest in human skin.

However, the dehydrated males approached Rasgon’s hand, with some even attempting to pierce his skin. One mosquito succeeded, managing to penetrate just the upper layer before being removed.

“I was completely shocked,” Rasgon said. “I wasn’t expecting that to happen at all.” The male mosquito’s long, thin mouthparts aren’t built to pierce deeply like a female’s, so they generally can’t draw blood on their own. However, Rasgon’s curiosity didn’t end there.

An Accidental Assist: Testing Blood-Feeding with a Scratch

To test whether male mosquitoes would take advantage of blood if it were more accessible, Rasgon unintentionally got help from his cat, “Jiji”, who scratched him. With an open wound on his hand, Rasgon allowed male mosquitoes access to the cut, and sure enough, the thirsty male mosquitoes “sipped blood” from the scratch.

These findings suggest that when male mosquitoes can’t meet their hydration needs from typical nectar sources, they might resort to blood-feeding. However, it appears to be more a response to “dehydration” than a true biological need for blood.

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A Role for Humidity Sensing in Male Mosquitoes’ Blood-Seeking

In another experiment, Rasgon’s team tested male Aedes aegypti mosquitoes that were genetically engineered to be unable to sense humidity. When these mosquitoes were exposed to low humidity, they did not increase their attempts to feed on blood, supporting the theory that “humidity detection” is crucial in driving male mosquitoes to seek out blood as a last resort.

While it has long been thought that blood would be “toxic” to male mosquitoes — with one previous study suggesting this for “male Culex quinquefasciatus mosquitoes” — Rasgon’s experiment revealed that blood-fed male “C. tarsalis” mosquitoes’ actually lived as long, or even a bit longer, than those who didn’t feed on blood.

Could Males Play a Tiny Role in Disease Transmission?

Female Aedes aegypti and Culex tarsalis mosquitoes are known vectors of serious diseases. “Aedes aegypti” is the primary carrier of yellow fever and is also responsible for spreading “Zika, chikungunya,” and “dengue”. Meanwhile, “female C. tarsalis” mosquitoes can transmit “West Nile virus, St. Louis encephalitis,” and other diseases.

Interestingly, Rasgon’s study revealed that “male C. tarsalis” mosquitoes, like females, could become infected with “West Nile virus” and even produce infectious virus particles in their saliva.

While the likelihood of male mosquitoes spreading disease is extremely low, this finding does open the door to more questions. Could there be rare cases where “dehydrated males”, desperate for moisture, feed on open wounds and inadvertently transfer viruses?

Reconsidering the Role of Male Mosquitoes

While Rasgon doubts that male mosquitoes will ever become significant players in disease transmission, his findings challenge the long-standing assumption that “male mosquitoes don’t feed on blood”.

The study suggests that in extreme circumstances, males may indeed turn to blood as a hydration source, meaning scientists should reconsider their role in mosquito ecology.

“Mosquitoes are more complex than we give them credit for,” Rasgon says. “This study suggests that male mosquitoes’ behavior may be more flexible than previously thought.”

Moving forward, researchers may need to examine whether, in certain rare cases, male mosquitoes could have a minor impact on “viral transmission” and whether environmental factors like humidity could influence their feeding behavior.

The Bigger Picture: Rethinking Mosquito Behavior

This discovery adds a surprising layer of complexity to mosquito behavior. Though male mosquitoes will almost certainly remain far less dangerous than females in terms of spreading disease, the study suggests that “environmental pressures” can significantly alter mosquito feeding habits.

This insight could be useful for future studies on “mosquito ecology” and “disease prevention” in regions where water scarcity or other environmental changes affect mosquito behavior.

In the end, Rasgon and his team have shown that even well-studied insects like mosquitoes still have secrets waiting to be uncovered and that even the least expected factors can influence their role in ecosystems — and potentially, in public health.