Halteres
Overview
 
Halteres are small knobbed structures modified from the hind wings in some two-winged insect
Insect
Insects are a class of living creatures within the arthropods that have a chitinous exoskeleton, a three-part body , three pairs of jointed legs, compound eyes, and two antennae...

s. They are flapped rapidly and function as gyroscope
Gyroscope
A gyroscope is a device for measuring or maintaining orientation, based on the principles of angular momentum. In essence, a mechanical gyroscope is a spinning wheel or disk whose axle is free to take any orientation...

s, informing the insect about rotation of the body during flight.

The halteres evolved from wings
Insect wing
Insects are the only group of invertebrates known to have evolved flight. Insects possess some remarkable flight characteristics and abilities, still far superior to attempts by humans to replicate their capabilities. Even our understanding of the aerodynamics of flexible, flapping wings and how...

. The ancestral insect species had two pairs of wings (like dragonflies
Dragonfly
A dragonfly is a winged insect belonging to the order Odonata, the suborder Epiprocta or, in the strict sense, the infraorder Anisoptera . It is characterized by large multifaceted eyes, two pairs of strong transparent wings, and an elongated body...

 and most other flying insect species have). In the Strepsiptera
Strepsiptera
The Strepsiptera are an order of insects with ten families making up about 600 species...

 (small insects parasitic on bee
Bee
Bees are flying insects closely related to wasps and ants, and are known for their role in pollination and for producing honey and beeswax. Bees are a monophyletic lineage within the superfamily Apoidea, presently classified by the unranked taxon name Anthophila...

s, wasp
Wasp
The term wasp is typically defined as any insect of the order Hymenoptera and suborder Apocrita that is neither a bee nor an ant. Almost every pest insect species has at least one wasp species that preys upon it or parasitizes it, making wasps critically important in natural control of their...

s and cockroach
Cockroach
Cockroaches are insects of the order Blattaria or Blattodea, of which about 30 species out of 4,500 total are associated with human habitations...

es), the forewings evolved into halteres, while in the Diptera
Fly
True flies are insects of the order Diptera . They possess a pair of wings on the mesothorax and a pair of halteres, derived from the hind wings, on the metathorax...

 (flies
Fly
True flies are insects of the order Diptera . They possess a pair of wings on the mesothorax and a pair of halteres, derived from the hind wings, on the metathorax...

, mosquito
Mosquito
Mosquitoes are members of a family of nematocerid flies: the Culicidae . The word Mosquito is from the Spanish and Portuguese for little fly...

es and gnat
Gnat
A gnat is any of many species of tiny flying insects in the Dipterid suborder Nematocera, especially those in the families Mycetophilidae, Anisopodidae and Sciaridae.In British English the term applies particularly to Nematocerans of the family Culicidae...

s), the hindwings changed into halteres.

In Diptera, the formation of the haltere during metamorphosis
Metamorphosis
Metamorphosis is a biological process by which an animal physically develops after birth or hatching, involving a conspicuous and relatively abrupt change in the animal's body structure through cell growth and differentiation...

 is dependent on the homeotic gene
Homeotic gene
Hox genes are a group of related genes that determine the basic structure and orientation of an organism.Hox genes are critical for the proper placement of segment structures of animals during early embryonic development Hox genes are a group of related genes that determine the basic structure and...

 Ultrabithorax
Ultrabithorax
Ultrabithorax or Ubx is a member of the homeobox gene family. Homeobox proteins function as transcription factors. In Drosophila melanogaster it is expressed in the third thoracic and first abdominal segments and represses wing formation. The Ubx gene regulates the decisions regarding the...

 (Ubx).
Encyclopedia
Halteres are small knobbed structures modified from the hind wings in some two-winged insect
Insect
Insects are a class of living creatures within the arthropods that have a chitinous exoskeleton, a three-part body , three pairs of jointed legs, compound eyes, and two antennae...

s. They are flapped rapidly and function as gyroscope
Gyroscope
A gyroscope is a device for measuring or maintaining orientation, based on the principles of angular momentum. In essence, a mechanical gyroscope is a spinning wheel or disk whose axle is free to take any orientation...

s, informing the insect about rotation of the body during flight.

The halteres evolved from wings
Insect wing
Insects are the only group of invertebrates known to have evolved flight. Insects possess some remarkable flight characteristics and abilities, still far superior to attempts by humans to replicate their capabilities. Even our understanding of the aerodynamics of flexible, flapping wings and how...

. The ancestral insect species had two pairs of wings (like dragonflies
Dragonfly
A dragonfly is a winged insect belonging to the order Odonata, the suborder Epiprocta or, in the strict sense, the infraorder Anisoptera . It is characterized by large multifaceted eyes, two pairs of strong transparent wings, and an elongated body...

 and most other flying insect species have). In the Strepsiptera
Strepsiptera
The Strepsiptera are an order of insects with ten families making up about 600 species...

 (small insects parasitic on bee
Bee
Bees are flying insects closely related to wasps and ants, and are known for their role in pollination and for producing honey and beeswax. Bees are a monophyletic lineage within the superfamily Apoidea, presently classified by the unranked taxon name Anthophila...

s, wasp
Wasp
The term wasp is typically defined as any insect of the order Hymenoptera and suborder Apocrita that is neither a bee nor an ant. Almost every pest insect species has at least one wasp species that preys upon it or parasitizes it, making wasps critically important in natural control of their...

s and cockroach
Cockroach
Cockroaches are insects of the order Blattaria or Blattodea, of which about 30 species out of 4,500 total are associated with human habitations...

es), the forewings evolved into halteres, while in the Diptera
Fly
True flies are insects of the order Diptera . They possess a pair of wings on the mesothorax and a pair of halteres, derived from the hind wings, on the metathorax...

 (flies
Fly
True flies are insects of the order Diptera . They possess a pair of wings on the mesothorax and a pair of halteres, derived from the hind wings, on the metathorax...

, mosquito
Mosquito
Mosquitoes are members of a family of nematocerid flies: the Culicidae . The word Mosquito is from the Spanish and Portuguese for little fly...

es and gnat
Gnat
A gnat is any of many species of tiny flying insects in the Dipterid suborder Nematocera, especially those in the families Mycetophilidae, Anisopodidae and Sciaridae.In British English the term applies particularly to Nematocerans of the family Culicidae...

s), the hindwings changed into halteres.

In Diptera, the formation of the haltere during metamorphosis
Metamorphosis
Metamorphosis is a biological process by which an animal physically develops after birth or hatching, involving a conspicuous and relatively abrupt change in the animal's body structure through cell growth and differentiation...

 is dependent on the homeotic gene
Homeotic gene
Hox genes are a group of related genes that determine the basic structure and orientation of an organism.Hox genes are critical for the proper placement of segment structures of animals during early embryonic development Hox genes are a group of related genes that determine the basic structure and...

 Ultrabithorax
Ultrabithorax
Ultrabithorax or Ubx is a member of the homeobox gene family. Homeobox proteins function as transcription factors. In Drosophila melanogaster it is expressed in the third thoracic and first abdominal segments and represses wing formation. The Ubx gene regulates the decisions regarding the...

 (Ubx). If this gene is experimentally deactivated, the haltere will develop into a fully developed wing. This is an excellent illustration of an important mechanism of evolutionary development
Evolutionary developmental biology
Evolutionary developmental biology is a field of biology that compares the developmental processes of different organisms to determine the ancestral relationship between them, and to discover how developmental processes evolved...

; a simple homeotic gene change can result in a radically different phenotype
Phenotype
A phenotype is an organism's observable characteristics or traits: such as its morphology, development, biochemical or physiological properties, behavior, and products of behavior...

.

Halteres flap up and down as the wings do and operate as vibrating structure gyroscope
Vibrating structure gyroscope
A vibrating structure gyroscope is a type ofgyroscope that functions much like the halteresof an insect.The underlying physical principle is that a vibratingobject tends to continue vibrating in the same planeas its support rotates...

s. Every vibrating object tends to maintain its plane of vibration if its support is rotated, a result of the Coriolis effect
Coriolis effect
In physics, the Coriolis effect is a deflection of moving objects when they are viewed in a rotating reference frame. In a reference frame with clockwise rotation, the deflection is to the left of the motion of the object; in one with counter-clockwise rotation, the deflection is to the right...

. If the body of the insect changes direction in flight or rotates about its axis, the vibrating halteres thus exert a force on the body. The insect detects this force with sensory organs
Sensory system
A sensory system is a part of the nervous system responsible for processing sensory information. A sensory system consists of sensory receptors, neural pathways, and parts of the brain involved in sensory perception. Commonly recognized sensory systems are those for vision, hearing, somatic...

 known as campaniform sensilla
Campaniform sensilla
Campaniform sensilla are mechanoreceptors found in insects. When the exoskeleton bends the resulting strain stimulates the sensilla. The displacement is transmitted down until it reaches the central nervous system. The term campaniform refers to the bell shape appearance of these sensory structures...

 located at the base of the halteres. The planes of vibration of the two halteres are orthogonal
Orthogonality
Orthogonality occurs when two things can vary independently, they are uncorrelated, or they are perpendicular.-Mathematics:In mathematics, two vectors are orthogonal if they are perpendicular, i.e., they form a right angle...

 to each other, each forming an angle of about 45 degrees with the axis of the insect; this increases the amount of information gained from the halteres.

Halteres thus act as a balancing
Balance (ability)
In biomechanics, balance is an ability to maintain the center of gravity of a body within the base of support with minimal postural sway. When exercising the ability to balance, one is said to be balancing....

 and guidance system
Guidance system
A guidance system is a device or group of devices used to navigate a ship, aircraft, missile, rocket, satellite, or other craft. Typically, this refers to a system that navigates without direct or continuous human control...

, helping these insects to perform their fast aerobatics
Aerobatics
Aerobatics is the practice of flying maneuvers involving aircraft attitudes that are not used in normal flight. Aerobatics are performed in airplanes and gliders for training, recreation, entertainment and sport...

. In addition to providing rapid feedback to the muscles steering the wings, they also play an important role in stabilizing the head during flight.

External links

The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
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