Zabalius aridus Ear Dorsolateral 2012 06 04 6748

CSIRO ScienceImage 2673 The Hearing Organs of Two Moths

A tympanal organ (or tympanic organ) is a hearing organ in

insects Insects (from Latin ') are hexapod invertebrates of the class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body (head, thorax and abdomen), three pairs of jointed ...

, consisting of a tympanal membrane ( tympanum) stretched across a frame backed by an air sac and associated

sensory neuron Sensory neurons, also known as afferent neurons, are neurons in the nervous system, that convert a specific type of stimulus, via their receptors, into action potentials or graded receptor potentials. This process is called sensory transduc ...

s. Sounds vibrate the membrane, and the vibrations are sensed by a

chordotonal organ Chordotonal organs are stretch receptor organs found only in insects and crustaceans. They are located at most joints and are made up of clusters of scolopidia that either directly or indirectly connect two joints and sense their movements relativ ...

Hymenoptera Hymenoptera is a large order of insects, comprising the 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 parasitic. Females typi ...

(bees, wasps, ants, etc.) do not have a tympanal organ, but they do have a Johnston's organ. Tympanal organs have evolved in at least seven different orders of insects. Tympanal organs can occur in just about any part of the insect: the

thorax The thorax (: thoraces or thoraxes) or chest is a part of the anatomy of mammals and other tetrapod animals located between the neck and the abdomen. In insects, crustaceans, and the extinct trilobites, the thorax is one of the three main di ...

, the base of the wing, the

abdomen The abdomen (colloquially called the gut, belly, tummy, midriff, tucky, or stomach) is the front part of the torso between the thorax (chest) and pelvis in humans and in other vertebrates. The area occupied by the abdomen is called the abdominal ...

, the legs, etc., depending on the group of insects. The structures are thought to have evolved independently many times. As a result, their position and structures are often used to help determine the

taxonomy image:Hierarchical clustering diagram.png, 280px, Generalized scheme of taxonomy Taxonomy is a practice and science concerned with classification or categorization. Typically, there are two parts to it: the development of an underlying scheme o ...

of the species. For example, all members of the

Geometridae The geometer moths are moth Moths are a group of insects that includes all members of the order Lepidoptera that are not Butterfly, butterflies. They were previously classified as suborder Heterocera, but the group is Paraphyly, paraphyleti ...

share distinctive paired abdominal tympanal organs that open towards the front side of the first abdominal segment. Within the organ, particular structures vary in shape and are used to indicate shared ancestry of subfamilies. In other families of

Lepidoptera Lepidoptera ( ) or lepidopterans is an order (biology), order of winged insects which includes butterflies and moths. About 180,000 species of the Lepidoptera have been described, representing 10% of the total described species of living organ ...

having abdominal tympanal organs, the opening may be in a different orientation and the structures differ in shape. Tympanal organs have evolved in Lepidoptera to allow them to detect the echolocation calls of predatory bats. The range of frequencies that the moth is most sensitive to is usually associated with the frequencies used in echolocation by the sympatric bat community. In the presence of predatory bats, it has been shown that the Lepidoptera species '' Mythimna unipuncta'' (true armyworm) stops mating behaviors, such as female calling and male wing flapping. As well, hearing is important for mating behaviors in this species because females increase their flapping frequency around males and males produce a trembling noise in response.

Anatomic terminology

Maes (1985) has provided an extensive overview of tympanal organs in the moth family

Pyralidae The Pyralidae, commonly called pyralid moths, snout moths or grass moths, are a family of Lepidoptera in the ditrysian superfamily Pyraloidea. In many (particularly older) classifications, the grass moths (Crambidae) are included in the Pyr ...

which also introduces some nomenclature: *tympanal membrane (tympanum): very thin

membrane A membrane is a selective barrier; it allows some things to pass through but stops others. Such things may be molecules, ions, or other small particles. Membranes can be generally classified into synthetic membranes and biological membranes. Bi ...

, transparent when dry, of the auditory organ *conjunctivum: membrane immediately connected with the tympanum *praecinctorium: median expansion of the intersegmental thoraco-abdominal membrane. In the Pyralidae type it is usually very simple. It is more developed in the

Crambidae Crambidae comprises the grass moth family of lepidopterans. They are variable in appearance, with the nominal subfamily Crambinae (grass moths) taking up closely folded postures on grass stems where they are inconspicuous, while other subfamilies ...

type. *intersegmental thoraco-abdominal membrane : intersegmental membrane between the metathorax and the first abdominal

sclerite A sclerite (Greek language, Greek , ', meaning "hardness, hard") is a hardened body part. In various branches of biology the term is applied to various structures, but not as a rule to vertebrate anatomical features such as bones and teeth. Instea ...

References

{{cite book , last1=Scoble, first1=MJ. , title=The Lepidoptera: Form, function, and diversity. , url=https://archive.org/details/lepidopteraformf0000scob, url-access=registration, year=1992 , publisher=Oxford Univ. Press, isbn=978-1-4020-6242-1 Insect anatomy Sensory organs in animals

Anatomic terminology

See also

References