Flies are a common sight, often observed rubbing their forelegs together. This complex and purposeful behavior plays a significant role in their daily existence. This article explores the mechanics and various purposes behind this frequent insect behavior.
The Mechanics of Fly “Hand” Rubbing
Flies rub their forelegs together in a rapid, coordinated motion. They also use these legs to brush other body parts, such as their head, antennae, and wings.
Their legs are equipped with specialized structures. The tarsi, or “feet,” possess fine hairs, bristles, and cushion-like pads called pulvilli. These structures, along with claws, enable flies to grip surfaces and aid in grooming.
The Primary Purpose: Keeping Sensory Organs Clean
The primary reason flies rub their legs is to clean their sensitive sensory organs. Flies depend on these organs to interpret their surroundings, locate food, find mates, and avoid threats. Many receptors are located on their legs and other body parts, making cleanliness paramount for their function.
Flies possess chemoreceptors, which are like taste and smell receptors, on their legs, feet, and proboscis. These allow them to “taste” surfaces, helping them determine if a substance is a suitable food source. Accumulations of dust, pollen, or other microscopic debris can clog these receptors, impairing a fly’s ability to accurately sense its environment and find sustenance.
Flies also have mechanoreceptors, which detect touch, movement, and vibrations, distributed across their body, including their legs. These help them perceive air currents, maintain balance, and detect potential dangers. Keeping these mechanoreceptors clear of foreign particles ensures their optimal performance for agile flight and quick escape from predators.
Grooming often follows a systematic pattern, beginning with cleaning the head, eyes, and antennae using the forelegs. The legs then rub together to remove the collected debris, sometimes transferring it to their mouthparts for disposal. This self-grooming maintains the acuity of their senses.
More Than Just Cleaning: Other Functions
While cleaning sensory organs is the primary purpose, fly leg rubbing serves additional functions that contribute to their survival and efficiency. The sticky pads on their feet, the pulvilli, secrete an adhesive fluid. Rubbing their legs helps to distribute this fluid, enhancing their ability to adhere to smooth surfaces and climb effectively.
Flies also use their forelegs as tools to clean other parts of their body that they cannot directly reach with their mouthparts. After cleaning their head and antennae, the forelegs are used to clean the mid-legs, and the hind-legs are employed to groom the wings and abdomen. This comprehensive grooming removes dust, dirt, and even pathogens like mold or fungi that could accumulate on their bodies and potentially cause illness.