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In entomology
Entomology () is the 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 as arach ...
, petiole is the technical term for the narrow waist of some hymenopteran insects, especially ants, bee
Bees are winged insects closely related to wasps and ants, known for their roles in pollination and, in the case of the best-known bee species, the western honey bee, for producing honey. Bees are a monophyly, monophyletic lineage within the ...
s, and wasps 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) forme ...
.
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) metasomal (posterior) segment of members of the hymenopteran suborderApocrita
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) forme ...
( ants, bee
Bees are winged insects closely related to wasps and ants, known for their roles in pollination and, in the case of the best-known bee species, the western honey bee, for producing honey. Bees are a monophyly, monophyletic lineage within the ...
s, and wasps). 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, but in entomology, that term is more correctly reserved for the second segment of the antenna; 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 ...
, ' pedicel' 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 an ...
) 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, 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 of paper wasp nests is also called a petiole.References
{{DEFAULTSORT:Petiole (Insect) Insect anatomy