Halteres

Flesh flies are among those that oscillate their halteres while walking, and also perform more poorly at certain walking tasks when their halteres are removed.

Interestingly, though halteres are coupled with the wings and with each other during flight, some flies oscillate their halteres while walking (without oscillating their wings).

What this means is that halteres beat up and down in time with the flapping of the wings along a linear pathway, but when the fly's body begins to rotate, the path of the beating halteres also changes.

Halteres were the dumbbells of the ancient Greek world.

An extreme example of this trait is in the family Syrphidae (hoverflies), where the bulb of the haltere is positioned nearly perpendicular to the stalk. citation Flies typically hold their halteres at a 90 degree offset.

Another structure in the class insecta also exists whose primary function is not the same as halteres, but that additionally serves a similar balancing function.

Because the halteres are set at different angles (90 degree offset), they also beat along two separate horizontal and vertical axes.

Brachyceran flies (short-antennaed) oscillate their halteres almost exactly opposite their wings (180 degrees).

Directions of rotation Halteres are able to sense small deviations in body position using the gyroscopic properties of moving mass.

Flies are also able to perform compensatory head movements to stabilize their vision without the use of their halteres.

Genetic studies have also brought to light many similarities between halteres and hindwings.

Halteres and vision both play a role in stabilizing the head.

He discovered that flies were unable to remain airborne when their halteres were surgically removed, but otherwise behaved normally. citation This result was initially attributed to the haltere's ability to sense and maintain equilibrium.

History Halteres were first documented by William Derham in 1714.

In 1917 v. Buddenbrock asserted that something else was responsible for the flies' loss of flight ability. citation He claimed that the halteres should instead be considered "stimulation organs".

In contrast, body rotations detected by the halteres elicit the greatest responses at higher angular velocities and degrade as the speed of rotation decreases.

In these individuals, halteres could thus be detecting sensory information during walking behavior as well.

It is commonly believed that the jumper would throw the weights behind him in midair to increase his forward momentum; however, halteres were held throughout the duration of the jump.

It is necessary for the halteres to be positioned like this in order to detect the three axes of motion.

Male strepsipterans uniquely possess two hindwings, while their forewings have taken on the club-like form of halteres. citation Though strepsipterans are very difficult to locate and are additionally rather short-lived, Pix et al.