13 types of insect antennae

The antennae are structures located in the anterior part of the head of the insects. They occur in pairs and are located near the eyes. Being mobile structures, they present joints, which allow rotational movements or in a single plane. The shape of the antennae is variable: those seen in the photograph are feather-shaped, and belong to a moth.

Due to the variety of shapes and sizes that they present, the antennae are used as a characteristic to identify and classify insects; They are also indicators of sexual dimorphism, that is, of characteristics that allow differentiating the sexes. In the case of antennae, those of the males are often more complex than those of the females.

functions

The antennae act mainly as touch receptors, thanks to the presence of hair-like sensory endings that cover almost the entire antenna, which are made up of mechanoreceptor cells, that is, they detect mechanical stimuli such as the sensation of textures.

They also function as olfactory receptors, through plate-shaped cells that can be located at the tip of each antenna and that are chemoreceptors, that is, sensitive to the presence of substances.

Some antennae may have an auditory function, through mechanoreceptors that detect mechanical stimuli from sound waves; others exhibit a grasping function during copulation, to hold the female. It has been reported that the antennae are also essential for recognizing other individuals, new habitats, and different species.

In insects such as bees, temperature and humidity receptors located at the tip of the antennae have been detected. In fact, it has been documented that these receptors can be of three types: some that respond to an increase in humidity, others to a decrease in temperature, and others to its increase.

Structure

The antennae are formed by a variable number of called knuckles or antennomers. In these structures three parts are distinguished, the first two can be uniarticulate, while the third presents a variable number of antennomeres organized in three divisions called scape, pedicel and flagellum.

The scape is the first division, it is joined by its lower end to the head of the insect; the pedicel is the smallest of the three divisions; the flagellum is the longest and, generally, the one that determines the types of antennae according to the number of segments, shapes and sizes.

Variety of antenna shapes

Among the most common forms of antennae are the following.

• The filiform antennae are thread-like. They are usually long, with a variable number of knuckles, which have an almost uniform diameter throughout their length. They are found in cockroaches.
• The clavate antennae have knuckles that increase in diameter as they move away from the base, thus taking the shape of a club or club. They are found in carrion beetles.
• The setiform antennae are bristle-shaped. This, because its segments decrease in diameter as they move away from the base. They are found in dragonflies.
• The awned antennae have a single long segment on the flagellum, from which a bare or hairy bristle is detached. They are common in flies.
• The capitate antennae have the last segments markedly thickened, giving them the shape of a club or club. They are common in butterflies.
• Lamellar antennae have tips in the form of lamellas or mobile plates, which are directed towards one side of the antenna. It is common to find them in beetles.
• The geniculate antennae are elbow-shaped. This is because the pedicel and the flagellum are perpendicular to the scape, which is quite elongated. They are found in ants.
• The pectinated antennae resemble a comb or comb. If the projections form on each side of the knuckles, they are known as bipectinate antennae. They are found in sawflies.2
• The feathery antennae have slender, hairy, angular extensions located on each side of the knuckles. In insects with this type of antennae, those of the males are more feathery than those of the females. They are frequent in moths.
• Serrated antennae have segments with very short extensions directed only to one side, giving them a saw-toothed or saw-toothed appearance. They are often found in shiny-shelled beetles.
• Moniliform antennae have spherical or oval flagellum segments, similar to pearls, giving them the appearance of a camandula. They are found in termites.
• The flabellate antennae have laminated projections on the pedicel, giving them a fan shape. They are found in beetles.
• The whorled antennae have hairs distributed in the same plane around each knuckle, similar to how the whorls are arranged in a plant, in which, for example, the leaves are arranged in the same plane around the stem. They are found in some mosquitoes.

Examples of some typical antenna shapes are presented below.

Sources

Álex E. Bustillo P. and Zulma Nancy Gil P. Characteristics of the class insecta . In Álex Enrique Bustillo Pardey (Ed). Insects and their management in Colombian coffee farming : 21–33, 2008.

De la Cruz, J. Entomology, Morphology, and Physiology of Insects . National University of Colombia., Bogota, 2005.

Francisco Padilla, Jose Manuel Flores, Antonio J. Perez. The sense organs of bees . The Apiary. 87: 13-26, 2007.

Randall, D., Burggren, W, French, K. Eckert Animal Physiology, Mechanisms, and Adaptations . 4th edition. McGraw Hill Inter-American., Madrid, 1998.

Triplehorn, C., Johnson, F. Borror, and DeLong’s Introduction to the Study of Insects . 7th edition. Cengage Learning., Boston, 2004.