A new study shows that deer keds, blood-feeding flies, scale back their visual capabilities after landing on a host and shedding their wings permanently. Researchers found that the insects reduce activity in key vision-related genes by about half. The change allows them to redirect energy toward feeding and reproduction.
Deer keds are found across Europe, Asia, Africa, and the Americas. As winged adults, they rely on flight and vision to locate hosts such as deer, and occasionally humans. Once settled, they lose their wings for life and live as parasites on the host's body. Scientists at Aberystwyth University and the University of Florence compared winged adults searching for hosts with wingless adults already on deer. They measured activity in opsin genes linked to visual sensitivity. Dr. Roger Santer, who led the research, said the flying stage resembles the vision system of tsetse flies. After wing loss, opsin gene activity drops to roughly half its previous level. He noted that the flies retain some vision but appear to trade sharpness for energy savings. The findings, published in the Journal of Experimental Biology, highlight how parasites adapt their senses to new lifestyles. Researchers suggest the work could aid future efforts to monitor and control biting flies.