Petiole (insect Anatomy) on:
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In entomology
Entomology () is the science, scientific study of insects, a branch of zoology. In the past the term "insect" was less specific, and historically the definition of entomology would also include the study of animals in other arthropod groups, such ...
, petiole is the technical term for the narrow waist of some hymenopteran
Hymenoptera is a large order (biology), order of insects, comprising the sawfly, sawflies, wasps, bees, and ants. Over 150,000 living species of Hymenoptera have been described, in addition to over 2,000 extinct ones. Many of the species are Par ...
insects, especially ant
Ants are eusocial insects of the family Formicidae and, along with the related wasps and bees, belong to the order Hymenoptera. Ants evolved from vespoid wasp ancestors in the Cretaceous period. More than 13,800 of an estimated total of 22 ...
s, bees, and wasp
A wasp is any insect of the narrow-waisted suborder Apocrita of the order Hymenoptera which is neither a bee nor an ant; this excludes the broad-waisted sawflies (Symphyta), which look somewhat like wasps, but are in a separate suborder. Th ...
s in the suborder Apocrita
Apocrita is a suborder of insects in the order Hymenoptera. It includes wasps, bees, and ants, and consists of many families. It contains the most advanced hymenopterans and is distinguished from Symphyta by the narrow "waist" ( petiole) formed ...
.
The petiole can consist of either one or two segments, a characteristic that separates major subfamilies of ants.
Structure
The term 'petiole' is most commonly used to refer to the constricted first (and sometimes second)metasoma
The metasoma is the posterior part of the body, or tagma, of arthropods whose body is composed of three parts, the other two being the prosoma and the mesosoma. In insects, it contains most of the digestive tract, respiratory system, and circula ...
l (posterior) segment of members of the hymenoptera
Hymenoptera is a large order (biology), order of insects, comprising the sawfly, sawflies, wasps, bees, and ants. Over 150,000 living species of Hymenoptera have been described, in addition to over 2,000 extinct ones. Many of the species are Par ...
n suborder Apocrita
Apocrita is a suborder of insects in the order Hymenoptera. It includes wasps, bees, and ants, and consists of many families. It contains the most advanced hymenopterans and is distinguished from Symphyta by the narrow "waist" ( petiole) formed ...
(ant
Ants are eusocial insects of the family Formicidae and, along with the related wasps and bees, belong to the order Hymenoptera. Ants evolved from vespoid wasp ancestors in the Cretaceous period. More than 13,800 of an estimated total of 22 ...
s, bees, and wasp
A wasp is any insect of the narrow-waisted suborder Apocrita of the order Hymenoptera which is neither a bee nor an ant; this excludes the broad-waisted sawflies (Symphyta), which look somewhat like wasps, but are in a separate suborder. Th ...
s). It is sometimes also used to refer to other insects with similar body shapes, where the metasomal base is constricted. The petiole is occasionally called a pedicel
Pedicle or pedicel may refer to:
Human anatomy
*Pedicle of vertebral arch, the segment between the transverse process and the vertebral body, and is often used as a radiographic marker and entry point in vertebroplasty and kyphoplasty procedures
...
, but in entomology, that term is more correctly reserved for the second segment of the antenna
Antenna ( antennas or antennae) may refer to:
Science and engineering
* Antenna (radio), also known as an aerial, a transducer designed to transmit or receive electromagnetic (e.g., TV or radio) waves
* Antennae Galaxies, the name of two collid ...
; while in arachnology
Arachnology is the scientific study of arachnids, which comprise spiders and related invertebrates such as scorpions, pseudoscorpions, and harvestmen. Those who study spiders and other arachnids are arachnologists. More narrowly, the study of sp ...
, 'pedicel
Pedicle or pedicel may refer to:
Human anatomy
*Pedicle of vertebral arch, the segment between the transverse process and the vertebral body, and is often used as a radiographic marker and entry point in vertebroplasty and kyphoplasty procedures
...
' is the accepted term to define the constriction between the cephalothorax and abdomen of spiders.
The plump portion of the abdomen posterior to the petiole (and postpetiole in the Myrmicinae
Myrmicinae is a subfamily of ants, with about 140 extant genera; their distribution is cosmopolitan. The pupae lack cocoons. Some species retain a functional sting. The petioles of Myrmicinae consist of two nodes. The nests are permanent and ...
) is called the gaster.
The structure of the petiole is an easy way to visually classify ants, because the major subfamilies of Formicidae have structural differences: some ants have two-segmented petioles, while others have a single-segmented petiole.
The only group other than ants known to ever possess a two-segmented petiole are wasps in the family Mymarommatidae
The Mymarommatidae, sometimes referred to as false fairy wasps. are a very small family of microscopic parasitic wasps. Only about half of the known species are living taxa (the others are fossils), but they are found worldwide.Gibson, G.A.P.; Re ...
, for which this is a diagnostic feature.
Other uses
Petiole may also be used in the context of wing veins, where a wing cell that is ordinarily four-sided is reduced to a triangle with a stalk (the cell thus being 'petiolate'). The stalk at the base ofpaper wasp
Paper wasps are Vespidae, vespid wasps that gather fibers from dead wood and plant stems, which they mix with saliva, and use to construct nests made of gray or brown papery material. Some types of paper wasps are also sometimes called umbrell ...
nests is also called a petiole.
References
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