The Fly That Gives Up Its Wings for Life
- Yul So
- Jun 11
- 2 min read
June 11, 2026
Yul So
For most insects, wings are essential for survival. For one blood-feeding parasite, however, they become useless the moment their mission is complete.
Researchers from the United Kingdom and Italy have discovered that the deer ked (Lipoptena andaluciensis), a small parasitic fly that feeds on mammal blood, undergoes a remarkable biological transformation after locating a host. Once it lands on a deer, the insect permanently sheds its wings and significantly reduces the activity of genes involved in vision.
Before finding a host, deer keds spend their adult lives flying through forests in search of large mammals. During this stage, they rely heavily on their visual system. Scientists found that winged deer keds possess a sophisticated set of visual genes similar to those found in tsetse flies, another group of blood-feeding insects known for locating hosts by sight.
The researchers identified five different opsin genes, which produce light-sensitive proteins responsible for detecting color, movement, and orientation during flight. However, once the insects settle into a deer's fur and become permanent external parasites, the expression of most of these genes drops dramatically, often to about half of previous levels.
According to the research team, maintaining advanced sensory systems requires considerable energy. After securing a host, deer keds no longer need to search for food or navigate long distances. Instead, they appear to redirect energy toward digestion, reproduction, and long-term survival on the host animal.
Interestingly, the insects do not completely shut down their visual systems. Scientists believe a limited ability to detect light may still be useful while moving through a host's fur or if they become separated and need to locate another host.
The study highlights how animals can adjust their sensory investments throughout life. Rather than maintaining the same abilities indefinitely, some species fine-tune their biology to match changing ecological demands, conserving energy where it is no longer needed.
