Entomology Glossary or Dictionary

Abdomen –

The third or posterior division of the insect body (the first two divisions being the head and thorax). It normally consists of nine or ten apparent segments.

Ambulatorial, Ambulatory –

Adapted for walking or making progress on a surface or substrate.

Anterior – At or towards the front.

Apterous, Apterus - Pertaining to insects without wings ; wingless.

Arbovirus – A virus spread by arthropods. Arbovirus is short for arthropod-borne virus. They are most commonly spread by blood-sucking insects such as mosquitoes. Arboviruses can cause minor illnesses such as mild fevers and rashes or they can cause potentially fatal illnesses such as encephalitis (inflammation of the brain).

Binomial Nomenclature –

The system of naming each type of organism (i.e. each species) by using two names: genus name and the specific epithet (species name).

Brachypterous –

Pertaining to insects with short or abbreviated wings. This term is often associated with insects that possess limited powers of flight.

Caste (pl. Castes) –

The various groups of matured individuals among social insects whose morphology or behaviour allows them to perform specialised labour within the colony. Workers, soldiers and reproductive queens are examples of castes.

Cercus (pl., Cerci) –

An appendage (generally paired) of the tenth abdominal segment (called a tergum). It is conventionally considered to be a sensory appendage that is usually slender, filamentous and segmented.

Chitin –

A colourless polysaccharide that serves as the major fibrous component of the insect cuticle or integument.

Class –

A division of the animal kingdom lower than a Phylum and higher than an Order. For example, the "Class Insecta" is a division of the Phylum Arthopoda.

Clypeus –

That part of the insect head below the frons (face) and above the labrum. The clypeus is highly variable in size and shape. For example, in the Diptera (flies, mosquitoes, etc.) the clypeus is often visible below the margin of the mouth as a visor-shaped piece.

Cochineal –

The dye made from the dried bodies of coccid Dactylopius coccus which feeds upon the Mexican Opuntia spp. (prickly pear cactus).

Collembola –

The Springtails. A Class or Order of species which are apterous (wingless), have mouthparts which are recessed within the head (entognathous), have no metamorphoses, have variably developed abdominal saltatorial appendages and a peculiar ventral tube (Collophore) on the first abdominal segment, which gives the group it's name.

Compound Eye –

Paired aggregations of separate visual elements known as ommatidia that are located on the insect head. Each pair of ommatidia corresponds with a single facet of the cornea.

Cornea - The outer, transparent surface of the compound eye.

Corpora allata - Small glands behind the brain that produce juvenile hormone.

Coxa (pl., Coxae) –

The basal segment of the insect leg, by means of which it is attached to the body. Coxae are paired, ventrolateral in position (i.e. attached to the side of the lower surface) and found on each thoracic segment.

Cursorial, Cursory –

Descriptive of legs adapted for running. Cursorial legs are typically long and tapered.

Cuticle - The external skeletal structure of the insect body. The cuticle is secreted by the epidermis, is composed of chitin and protein and consists of several differentiated layers.

Diapause - A state of suspended animation. During diapause, development, growth and metabolic activity are reduced. In some insects diapause is obligate, while in others it is dependent on external stimuli and is regarded as an adaptation to increase the probability of survival during environmentally unfavourable conditions because it allows the insect to keep its life cycle synchronised with seasonal progression.

Distal - Near or toward the free end of an appendage ; that part of a segment farthest from the body.

Dorsal - Of or belonging to the upper surface.

Dorsal Vessel - The major structural component of an insect's circulatory system. The dorsal vessel is a tube that runs longitudinally through the thorax, abdomen and along the inside of the dorsal body wall. Its function is to collect haemolymph in the abdomen and conduct it forward to the head.

Elytron (pl. Elytra)- The forewings of Coleoptera (beetles). Elytra are leathery or chitinous covers that serve as protection for the hind wings. The elytra are not used in active flapping during flight, but when the beetle is at rest they normally meet in a straight line down the middle of the dorsum (upper surface).

Epicuticle - The rigid outermost layer of cuticle, lying above the procuticle.

Epithelial - Of or pertaining to the epithelium e.g. epithelial cells.

Epithelium - Membranous tissue that forms a continuous layer covering internal or external surfaces of multicellular organisms.

Excretion - The loss of ions, solutes, water and metabolic wastes from the body.

Family - In zoological classification, a level of the taxonomic hierarchy below the Order and above the Genus. All zoological Family names end in the suffix '-idae'.

Femur (pl., Femora) - The third segment of the insect leg ('the thigh'). The femur is usually the largest and most variably shaped segment of the leg. It is attached to the body through trochanter and coxa and bears the tibia at it's distal (furthest) end.

Flagellum - That part of the antenna beyond the pedicel.

Fossorial - Descriptive of structures modified for digging or burrowing.

Frenulum – The spine, simple in males, compound in females, arising from the base of the hind wings in many Lepidoptera (moths, butterflies) and projecting beneath the forewing. The frenulum is comprised of one or a group of fused setae (bristles) and it's function is to unite the wings in flight;
- in Cicada, the frenulum is the triangular lateral piece on the mesonotum (middle back) which connects with the trochlea (thickened base of the hind wings).

Gall - An abnormal growth or swelling of plant tissue, caused by stimuli external to the plant itself, generally by insects such as the gall wasp and gall midge ; sometimes by bacteria, parasitic fungi or other diseases of the plant.

Genus - An assemblage of Species agreeing in one character or a series of characters. It is usually considered arbitrary and opinionative grouping, though some consider it a natural assemblage.

Haemocoel, Hemocoel - In insects, the haemocoel is the main body cavity. The haemocoel is filled with haemolymph and contains the soft internal organs.

Haemolymph, Hemolymph - The blood-like nutritive fluid found in lower invertebrates with open circulatory systems. The fluid fills the entire body cavity (haemocoel) and surrounds all cells. Haemolymph consists of water, inorganic salts (Na, Cl, K, Mg, and Ca), and organic compounds (carbohydrates, proteins, and lipids).

Haltere (pl. Halteres) - The structurally and functionally modified hind wing of Diptera (true flies). The haltere is a balancing organ used to maintain stability during flight. Halteres vibrate at the same frequency as the forewings but in anti-phase (i.e. when the forewing is up, the haltere is down and vice versa).

Hamulus (pl. Hamuli) - Any small hook or hook-like process;

- in Odonata (dragonflies and damselflies) , it is an unusually forked appendage of the second segment of the male, also termed genital hamule or hamules;

- in Hymenoptera (ants, bees and wasps), the hamuli are minute hooks at the front edge of the hind wings which temporarily attach to the forewings while in flight;

- in tree-crickets, they are the hook like processes of the genitalia.

Hemelytron (pl. Hemelytra, Hemielytra) –

The forewing in the Heteroptera (a suborder of insects in which the forewings have different textures). The basal (bottom) half of the wing is thickened and the apical (top) part is membranous ; some authors consider 'elytron' or 'tegmen' to be synonymous with Hemelytron ; it is also sometimes applied to the tegmen of Orthoptera (crickets, katydids, grasshoppers etc).

Hemimetabolous - Insects with incomplete metamorphosis, where the individual develops with gradual changes in size and shape. There are three distinct stages in the development of a hemimetabolous insect: egg, nymph (juvenile of any instar) and adult.

Hermaphrodite - An individual that possesses both male and female reproductive organs.

Holometabolous - Insects with complete metamorphosis, where the body form changes abruptly. Holometabolous insects have four distinct forms during their life cycle: egg, larva, pupa and adult.

Honey - The thickened and partly digested nectar of flowers produced by adults of various bees which is used as food for the larvae.

Instar - The growth stage between two successive moults.

Integument - The outer covering or cuticle of the insect body. It is a multi-layered, composite organ which defines the body shape, size and colour. Integument is composed of living epidermal cells and their secretions. Each layer is a different thickness, chemical composition and displays physical properties different from surrounding layers.

Juvenile hormone (JH) –

Hormone released by the corpora allata into the haemolymph. Juvenile hormone suppresses the development of adult characters and the amount of juvenile hormone released determines the outcome of a moult.

Labium - A compound structure which forms the 'lower lip' or floor of the mouth in mandibulate insects (i.e. insects with biting jaws). It is positioned behind the first maxilla and opposite the labrum. The labium is often regarded as the 'second maxilla' and is also sometimes referred to as the 'tongue'.

Labrum - The 'upper lip' of the insect head, covering the base of the mandible and forming the roof of the mouth.

Larva - An immature stage of a holometabolous insect that is morphologically distinct from the adult form. The larval stage of development follows the egg stage and precedes the pupal stage.

LD 50 - The dose of an insecticide that will kill 50% of the test organisms to which it is administered. It is measured as milligrams of insecticide per kilogram of body weight.

Leaf Miner - An insect, usually in its larval stage, that uses its mouthparts to create a tunnel between the upper an lower surfaces of a leaf.

Lateral - Descriptive of structure or movement to the side.

Malpighian Tubules - The main excretory organs of insects. They primarily function in elimination of nitrogenous wastes and the maintenance of internal ionic balance.

Mandibles -

The first pair of jaws in insects. The mandibles are laterally positioned behind the labrum. They vary in size, shape and are highly modified in form. Mandible shape is strongly influenced by function, for example, in chewing insects the mandibles are stout and tooth-like, while in piercing/sucking insects they are needle- or sword-shaped. Mandibles are not used exclusively for feeding. For example, some bees and wasps use them to construct nests in soil, wood and other hard materials.

Maxilla (pl. Maxillae) -

The paired lateral accessory jaws located immediately posterior of (behind) the mandibles. The maxillae are the second pair of jaws in a mandibulate insect (i.e. insect with biting jaws) and they are structurally more complex than the mandibles.

Mesothorax -

The second or middle thoracic segment which bears the middle legs and the anterior wings. See mesothorax and prothorax.

Metamorphosis - The physical transformation an insect undergoes during successive stages of development.

Metathorax -

The third thoracic segment which bears the hind legs and second pair of wings. The metathorax is variable in structure: it may be distinct from the mesothorax, it may be closely united with the mesothorax or in some species it may appear as part of the abdomen. See prothorax.

Micropyle - A small opening at the anterior end of an insect egg that allows the entry of sperm for fertilisation.

Monoculture - Growth of a single species in a particular area.

Moult - The process by which insects shed elements of the integument during growth.

Natatorial -

Descriptive of swimming or adaptations for locomotion in water. This term is generally applied to swimming legs in subaquatic insects.

Nematode -

A worm that belongs to the phylum Nematoda. Nematodes have unsegmented, cylindrical bodies, often narrowing at each end. Many species are parasitic e.g. hookworm.

Neurone (Neuron) -

An entire nerve cell, including the neurocyte, axon and dendrites. The cell body is called the neurocyte and it has a number of branches extending from it. The primary branch is called the axon and it directs electrical impulse away from the cell body while the smaller branches are called dendrites and they receive stimuli from adjacent cells.

Notum - The dorsal or upper part of a body segment, particularly of the thorax. See tergum.

Nymph - An immature insect after emerging from the egg. This term usually refers to insects in which there is incomplete metamorphosis (see hemimetabolous).

Ocellus (pl. Ocelli) -

The 'simple eye' of many adult insects which consists of a single bead-like lens. Insects may have a single ocellus or they may have a small group of ocelli (up to three). Ocelli may also be absent in some insects.

Omnatidium (pl. Ommatidia) -

The basic visual element that forms the compound eye. The omnatidium is composed of a lens, cone, rhabdom and pigment cells. The size, shape and number of ommatidia that form the compound eye vary among species.

Order -

One of the primary taxonomic divisions below Class level and above Family level. In Class Insecta, the division of Order was originally based on wing structure with ordinal names usually ending in -ptera e.g. Order Diptera.

Ovipositor -

An egg-laying tube of the female insect's abdomen. The morphology of the ovipositor varies among species: it may be fixed and rigid in length or it may be flexible and telescopic. The ovipositor is not present in all insect species.

Parthogenesis - Reproduction without fertilization. Individuals develop from an unfertilised egg.

Pedicel -

Generally a stalk or stem supporting an organ or other structure;
- the second segment of the insect antenna, forming the pivot between
the scape and the flagellum.

Phylum - A category used in biological classification, below Kingdom level and above Class level.

Phytophageous - Descriptive of organisms that feed on plant tissue.

Pheromone - Hormone released into the environment for chemical communication between insects.

Pleuron (pl. Pleura) - The lateral region of any segment of the insect body, usually of the thoracic segments.

Pollination - The process in which pollen of flowering plants is transferred by animals, air or water currents to the stigma for fertilisation.

Polyphageous -

Pertaining to organisms that feed on a range of food sources i.e. they have an unspecialised diet (omnivorous). For example, polyphageous may be used to describe an herbivorous insect that feeds on a range of plant species, a predator that feeds on many species of prey, or a parasite that feeds on many species of host.

Procuticle -

The inner layer of the insect cuticle that lies directly above the epidermis. The procuticle is differentiated into two layers: a hard, outer exocuticle and a soft, inner endocuticle.

Proleg (pl. Prolegs)-

In general, any process or appendage that serves the purpose of a leg;
- specifically, the fleshy non-segmented abdominal legs of caterpillars and certain sawfly larvae. Prolegs are not true segmented appendages and can be considered 'false legs'.

Prothorax -

The first thoracic segment, or portion of the thorax nearest the head. The prothorax bears an anterior pair of legs but does not bear wings. See mesothorax and metathorax.

Protura -

A Class and Order of minute insects, chiefly categorised by entognathous mouthparts (i.e. mouthparts recessed within the head), lack of antennae and compound eyes. Protura is sometimes considered a primitive Order of Insecta.

Pupa -

the inactive state between larva and adult in holometabolous insects. During pupation, the larva transforms into the adult.

Raptorial -

Adapted for seizing prey ; predaceous. Usually used to describe insect legs with opposable spines or elongate appendages that are adapted for impaling prey.

Reticulate - Descriptive of surface sculpture, usually of the insect's integument, that is covered with a network of lines.

Rickettsias -

Bacteria belonging to the genus Rickettsia. Species of Rickettsia are carried as parasites by many ticks, fleas, and lice, causing diseases such as typhus.

Saltatorial -

Adapted for leaping or having the power of leaping. Usually used to describe insects that have anatomical adaptations and a behavioural predisposition to leap, jump or hop.

Scape -

The basal segment of the antenna (i.e. closest to the insect head). The scape is typically one of the longest segments of the antenna, often cylindrical in shape and containing musculature that originates in the insect head.

Sclerite (pl. Sclerites) -

Any hard portion of the insect integument separated from similar areas by membrane or suture (seam). Sclerites, also called 'plates', are variable in shape and have a different name, depending on the region of the body in which they are located.

Shellac -

Commercially cleaned lac made into flakes or sheets. Lac is the yellowish/reddish-brown resinous substance produced from the epidermal glands of the lac insect, Tacchardia lacca. Lac is a resin that has many industrial and scientific uses.

Silk -

The hardened salivary secretion of certain larvae, mainly of Lepidoptera (butterflies and moths). Silk is composed of two proteins, Fibroin and Sericin, and is secreted in liquid form which hardens into silk threads when exposed to the air.

Species -

The basic unit of biological classification. Generally defined as an aggregation of individuals similar in appearance and structure, mating freely and producing young that themselves mate freely and bear fertile offspring. Abbreviated to sp. for one species and spp. for two or more species.

Spermatophore -

A packet or capsule containing sperm that is transmitted to the female during copulation. Spermatophores are manufactured by the accessory glands of the male reproductive system.

Spiracle –

A breathing pore or aperture. Spiracles are paired, lateral holes in the plural (side) wall of insect body segments and are the means by which air enters the tracheal (respiratory) system.

Stem Borer -

An insect which spends all or part of its life cycle within the stem or root of a plant, feeding on the plant tissue by using its mouthparts to bore through it.

Sternum -

The entire ventral division of any body segment. Specifically and in general usage, the sternum is the underside of the insect thorax, between the coxal cavities.

Synapse - A small area of close contact between terminal fibres of two or more neurones, across which information is transmitted.

Synergism -

The phenomenon in which the combination of two or more substances (e.g. chemicals) achieves a greater effect than the sum total effectiveness of each individual substance.

Synergist -

A non-toxic chemical in an insecticide which increases the potency of that insecticide when the two are mixed. See synergism.

Systemic Insecticide -

(1) An insecticide applied to an organism (plant or animal) which is then translocated throughout its body tissues, thus rendering it poisonous to insects feeding on that organism;

(2) An insecticide that enters a plant through leaves, branches or roots and spreads throughout the plant in order to protect it from insects.

Tarsus (pl. Tarsi) -

The insect's foot. The tarsus is a jointed appendage attached to the tibia and often bearing claws and other structures. Typically, the tarsus consists of 1-5 segments or joints which are called tarsomeres.

Tarsomere (pl. Tarsomeres) -

Any of the sub-segments of the tarsus in the insect foot. Tarsomeres lack their own musculature and so are not true morphological segments.

Tegmen (pl. Tegmina) -

A covering;
- the hardened, leathery forewing in Orthoptera, Blattaria and some Hemiptera. It is also sometimes applied to
the hemelytra of Heteroptera.

Tergum - The upper, or dorsal, surface of any body segment of an insect, consisting of one or more sclerites.

Thorax -

The second or intermediate region of the insect body bearing the true legs and wings. The thorax is composed of three segments: prothorax, mesothorax and metathorax. Each of these segments is composed of three components: a dorsal (upper surface) sclerite, a lateral or pleural sclerite and a ventral (lower surface) sclerite. See abdomen.

Tibia - The fourth segment of the insect leg. The tibia is typically long, slender and is located between the femur and the tarsus.

Trachea - A tubular structure of the insect gas exchange system. Tracheae are elastic, spirally ringed tubes that allow gases to move throughout the insect body.

Tracheole –

One of the fine branching tubes of the trachea of the insect respiratory system. Each tracheole connects to a single cell of the insect body, facilitating gas exchange.

Trochanter -

The second and typically smallest segment of the insect leg. It is positioned between the coxa and femur. The trochanter on all legs of most insects is composed of one segment. However, in some species the trochanter is fused with the femur and in others it appears to be segmented.

Urtication -

The rash produced by certain insects by means of poisonous hairs or secretions.

Vector -

Any organism which transports or transmits a parasite to a host. In medical entomology, a vector is an arthropod which carries disease producing organisms to a vertebrate host.

Ventral - Towards or at the lower surface.


Gordh, G. & Headrick, D. (2001). A Dictionary of Entomology. CABI Publishing, New York.

Knox, R. B., Ladiges, P. Y., Evans, B. K. (1994). Biology. McGraw Hill, Sydney.

Torre-Bueno, J. R. (1978). A Glossary of Entomology. New York Entomological Society, New York.

Shamim Ahmed