Living With Halteres III

Robber fly

Diogmites angustipennis,
The “Hanging Thief”, Robber fly

The fly haltere is a remarkable structure that changes the function of the hind wing from motion production into a sensor. Most insects move their wings by vibrating the thorax. Both forewing and hindwing move up and down in phase. A fly that beats its wings several hundred times per second will move its halteres at the same rate. Instead of a wing shape similar to the forewing, a fly haltere is a stalk with a ball on the end. When a fly turns in flight, the turn places a force on the haltere due to the Coriolis effect. (The haltere tends to keep moving in the same plane and the turn causes the haltere to bend relative to the fly’s body.) The force on the haltere stretches the sensor at its base during a turn. This signals to the fly that its direction of motion has changed.

A flying object can rotate around one of three axes defined as roll, pitch and yaw. Although the force on a haltere can be applied along all 3 axes, the measurement of that force is made by the two-dimensional stretch receptor at the base of the haltere. A single haltere has only two measuring axes. However, halteres are not positioned in a linear fashion and do not beat in parallel planes. They are typically offset by 120 degrees instead of 180 degrees. Thus, the halteres sense movements along two horizontal axes and two vertical axes. The separate signals from the two halteres are integrated in the fly nervous system to give roll, pitch and yaw information. The integration makes a fly more sensitive to changes in pitch than changes in roll.

A fly with one haltere can get some information on change in its flight attitude so it can still fly. A fly with no halteres is flying without sensors. The fly uses feedback from the halteres to make adjustments in body position that keep it airborne. Without information, the fly cannot prevent assuming unstable postures that cause it to fall through from the air.

About jjneal

Jonathan Neal is a retired Associate Professor of Entomology at Purdue University and author of the textbook, Living With Insects (2010). This blog is a forum to communicate about the intersection of insects with people and policy. This is a personal blog. The opinions and materials posted here are those of the author and are in no way connected with those of my employer.
This entry was posted in behavior, by jjneal, Taxonomy. Bookmark the permalink.

3 Responses to Living With Halteres III

  1. Pingback: Fly Flight Coordination | Living With Insects Blog

  2. Insects and more! says:

    I wonder if Strepsiptera halteres also work the same way and what the advantages or disadvantages of having halteres that take the place of forewings instead of the hindwings?
    I’ve never thought of Streps to be as versatile and agile fliers as flies though…

    • jjneal says:

      Strepsispterans are tiny and cannot be as agile as house flies
      Strepsispteran forewings are sensory and analogous halteres which are the hindwings of Diptera. This seems to be a case of two groups independently arriving at similar function but using different wings.

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