Glossary

Terms used in aphid morphology

Some of the following terms and definitions are modified from the references listed at the bottom of the page. Some terms are illustrated in the morphology pages; links to these are provided below.

A

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Abdomen(s)

Third main body region of the aphid, consisting of eight segments.

Abdominal

Pertaining or belonging to the abdomen.

Abdominal striation(s) (Image)

A row of polygonal ridges, bearing shortened spines, on the dorsal lateral surface of abdominal segments 5-7 for stridulation. See rastral spines.

Accessory sensorium (sensoria)

A small cluster of primary sensoria adjacent to a larger primary sensorium, both occurring on the distal end of the base of the terminal antennal segment.

Accessory seta(e) (Image)

Seta between the basal and apical primary setae on the fourth rostral segment. Also known as secondary setae.

Alata(e) (Image)

An aphid with wings, except in aberrant cases always an adult.

Alatoid

Describing a nymph bearing wing pads destined to become an alata.

Anal

Of or pertaining to the anus.

Anal plate(s)

A sternite of variable shape and size ventral to the anus.

Annular (Image)

Describing a ringlike structure such as an annular sensorium encircling the antenna.

Antenna(e) (Image)

The first appendage of the head of the insect.

Antennal

Of or pertaining to the antenna.

Antennal socket(s)

The opening in the head where the antenna is connected.

Antennal tubercle(s)

An extension of the head near the medial margin of the antennal socket.

Antennomere(s)

Any of the five or six "segments" of the antenna.

Antesiphuncular sclerite(s) (Image)

A sclerite on the abdominal dorsum immediately in front of the base of the siphunculus.

Anus(es)

The opening between the cauda and the anal plate.

Apex (apices)

The far distal end of a structure. Opposite of base.

Apical

Of or pertaining to the apex, as in the apical setae found at the very distal tip of the processus terminalis of the antenna. Opposite of basal. See also distal, terminal, and ultimate.

Aptera(e) (Image)

An adult without wings.

B

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Basal

Of or pertaining to the base, as in the first, or basal segment of an appendage. Opposite of terminal and apical. See also proximal.

Base(s)

The bottom end of a structure or appendage. The term is often used to describe that portion of the terminal antennal segment that is not the processus terminalis (Image).

Basitarsus (basitarsi) (Image)

Conjunction of basal and tarsus. The first tarsomere. Also known as the first tarsal segment or tarsus 1.

C

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Capitate

Describing an enlarged or bulbous apex, such as a capitate seta.

Cauda(e) (Image)

A taillike process or extension of the eighth abdominal segment.

Cephalic

Pertaining or belonging to the head.  

Clonal

Of or pertaining to one or more clones.

Clone(s)

The genetically identical offpsring, through any number of generations, of a single vivipara. Many (but not all) aphid colonies are composed of clones. Clonal lineages can extend, through parthenogenesis, for many generations and even across many years. The term usually refers to an individual aphid, but can also refer to the entire genetically homogeneous lineage.

Clypeus (clypei)

A large plate on the ventral aspect of the head at the base of the rostrum. It is swollen in aphids to hold large sucking muscles.

Colony (colonies)

A group of aphids found together at the same location on the same host. A colony is often composed entirely of a single vivipara and her clonal offspring. However, mixed colonies, either of different clonal lineages of the same species or of different species are common.

Compound eye(s)

An aggregation of individual ommatidia located on the head.

Cornicle(s) (Image)

Paired cylindrical chambers on the dorsal surface of sixth abdominal segment from which alarm pheromones are expelled. See siphunculus.

Coxa(e) (Image)

The basal segment of the leg. It is attached basally to the body proper and distally to the trochanter.

Coxal

Of or pertaining to the coxa.

Cubitus (cubiti)

The middle crossvein of the forewing and the basal crossvein of the hindwing.

Cuticle(s)

The outer noncellular layers of the exoskeleton secreted by the epidermal cells.

D

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Distal

Of or pertaining to a position further away, as in towards the apex of an appendage. Opposite of proximal. See also terminal and ultimate.

Distitarsus (distitarsi) (Image)

Conjunction of distal and tarsus. The last tarsomere, bearing paired claws apically. Also known as the second tarsal segment or tarsus 2.

Dorsal

Pertaining to the upper surface of the body or structure.

Dorsal suture(s)

Medial longitudinal line separating the head into two halves.

Dorsum (dorsa)

The back of the insect. See also tergum.

E

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Embryo(s)

An immature insect developing within an egg or its parent prior to birth.

Eye(s)

Any of several organs on the head used in vision. These may be the compound eye, with or without triommatidium, or ocellus.

F

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Facet(s)

The surface of an ommatidium of the compound eye.

Femoral

Of or pertaining to the femur.

Femur(s, femora) (Image)

The third and usually the most massive segment of the leg. It is attached basally to the trochanter and distally to the tibia.

Flagellomere(s)

Individual segments of the flagellum of the antenna, distal to the scape and pedicel.

Flagellum(s, flagella) (Image)

The entire portion of the antenna distal to the pedicel or second segment.

Foreleg(s); Fore leg(s)

One of the first pair of legs, located on the prothorax.

Forewing(s); Fore wing(s)

One of the larger pair of wings attached to the mesothorax. See also hindwing.

Frons (frontes) (Image)

The most forward-facing aspect of the head.

Fundatrix (fundatrices)

The viviparous aphid that hatches from an egg and founds a new aphid colony.

G

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Genital plate(s) (Image)

A ventral sclerite (sternite), variable in size and shape, in front of the genital opening. It is present only in adults.

Gonapophysis (gonapophyses) (Image)

Reduced genitalia consisting of several seta-covered bumps in the hind region of an adult female. Usually referred to as rudimentary gonapophysis.

H

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Hair(s)

Incorrect term sometimes used in place of seta.

Head(s)

The first or most anterior region of the body, bearing primary sense organs.

Hindleg(s); Hind leg(s)

One of the third pair of legs, located on the metathorax.

Hindwing(s); Hind wing(s)

One of the smaller pair of wings attached to the metathorax. See also forewing.

Honeydew(s)

Aphid excrement made sweet by the concentration of sugars in plant phloem. Honeydew is implicated in the growth of molds that can harm plants. It attracts ants, which often form mutualistic symbioses with aphids, whereby the ants "milk" the aphids for their honeydew, and in return defend the aphids from predators.

I

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Imbrication

Small ridges covering a surface, such as that of a siphunculus (e.g., imbricated siphunculus contrasts with smooth siphunculus).

Immature(s)

An individual younger than adult. An embryo or nymph.

Instar(s)

The stage between molts of an immature insect. Most aphids have three or four instars before reaching adulthood.

J

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K

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L

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Lateral

Pertaining to the side of the body or structure. See also marginal.

Larva(e)

A term used to describe the immature stage of a holometabolous insect (an insect that goes through complete metamorphosis). It is sometimes incorrectly used instead of "nymph" to describe an immature aphid.

Leg(s) (Image)

One of six ambulatory appendages of the thorax. Each leg is composed of the coxa, trochanter, femur, tibia, basitarsus, distitarsus, and tarsal claw.

M

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Margin(s)

The side of the body or a structure.

Marginal

Of or pertaining to the margin. See also lateral.

Media(e)

Basal stalk, arising near the base of the pterostigma of the forewing, from which produces 2-3 branches extending to the wing margin. The distal crossvein of the hindwing.

Medial

Of or pertaining to the midline of the body or the middle of a structure.

Mesocoxa(e)

The coxa of the mesothorax, or the coxa of the midleg.

Mesofemur(s, mesofemora)

The trochanter of the mesothorax, or the femur of the midleg.

Mesotarsus (mesotarsi)

The tarsus of the mesothorax, or the tarsus of the midleg.

Mesothoracic

Of or pertaining to the mesothorax.

Mesothorax(es, mesothoraces)

The middle segment of the thorax, bearing the forewings and the midlegs.

Mesotibia(s,e)

The tibia of the mesothorax, or the tibia of the midleg.

Mesotrochanter(s)

The trochanter of the mesothorax, or the trochanter of the midleg.

Metacoxa(e)

The coxa of the metathorax, or the coxa of the hindleg.

Metafemur(s, metafemora)

The femur of the metathorax, or the femur of the hindleg.

Metatarsus (metatarsi)

The tarsus of the metathorax, or the tarsus of the hindleg.

Metathoracic

Of or pertaining to the metathorax.

Metathorax(es, metathoraces)

The third segment of the thorax, bearing the hindwings and the hindlegs.

Metatibia(s,e)

The tibia of the metathorax, or the tibia of the hindleg.

Metatrochanter(s)

The trochanter of the metathorax, or the trochanter of the hindleg.

Midleg(s); Middle leg(s)

One of the second pair of legs, located on the mesothorax.

N

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Nymph(s)

An individual developmentally between the embryo state and adulthood. See also immature.

O

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Ocellus (ocelli) (Image)

A simple ocular lens on the head. Normally there are three ocelli in alatae, none in apterae.

Ocular

Of or pertaining to the eye.

Ocular tubercle(s) (Image)

Tubercle at the base of the compound eye bearing the triommatidium.

Ommatidium (ommatidia)

A single unit of the compound eye.

Ovipara(e) (Image)

A female adult capable of producing eggs. Contrasts with vivipara.

P

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Parthenogenesis

Asexual reproduction. Most aphid reproduction is parthenogenetic, vivipara producing clonal offspring throughout most of the year, with sexual reproduction occurring at the end of the growing season.

Pedicel(s)

The second segment of the antenna between the scape and the flagellum.

Postsiphuncular sclerite(s) (Image)

A sclerite on the abdominal dorsum immediately behind the base of the siphunculus.

Preapical

Of or pertaining to a position basal to the apex. See also subapical.

Primary sensorium (sensoria)

A circular sensorium occurring often on the subapical part of the fifth antennal segment and always on sixth antennal segment.

Primary seta(e) (Image)

Collectively, the basal and preapical pairs of setae on the fourth rostral segment.

Processus terminalis (processi terminalis) (Image)

The slender apical part of the sixth antennal segment distal to the primary sensorium on the thickened base.

Procoxa(e)

The coxa of the prothorax, or the coxa of the foreleg.

Profemur(s, profemora)

The femur of the prothorax, or the coxa of the foreleg.

Pronotum (pronota)

The dorsal portion of the prothorax.

Protasus (protarsi)

The tarsus of the prothorax, or the tarsus of the foreleg.

Prothoracic

Of or pertaining to the prothorax.

Prothorax(es, prothoraces)

The first segment of the thorax, bearing the forelegs.

Protibia(s,e)

The tibia of the prothorax, or the tibia of the foreleg.

Protrochanter(s)

The trochanter of the prothorax, or the trochanter of the foreleg.

Proximal

Of or pertaining to a position closer in, as in towards the base of an appendage. Opposite of distal. See also basal.

Pseudosensorium (pseudosensoria) (Image)

Scent glands on the metatibiae of oviparae (also rarely on viviparae), similar in appearance to rhinaria.

PT

Abbreviation for processus terminalis.

Pterothoracic

Of or pertaining to the

Pterothorax(es, pterothoraces)

The wing-bearing segments of the thorax, i.e., the mesothorax and metathorax together.

Pterostigma(s,ta)

A thickened part of the forewing membrane along the costa extending from a point near the base of the media to slightly beyond the radial sector. See stigma.

Q

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R

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Radial sector(s)

The branch of the radius in the forewing and hindwing.

Radius (radii)

The second vein of the forewing and hindwing, posterior to the costa, fused with the subcosta, media, and cubitus.

Rastral seta(e) (Image)

A row of peglike setae on the inner surface of the metatibiae for stridulation. See tibial peg.

Rastral spine(s) (Image)

A row of polygonal ridges, bearing shortened spines, on the dorsal lateral surface of abdominal segments 5-7 for stridulation. See abdominal striation.

Reticulation(s) (Image)

Pattern of connected polygons. In aphids usually associated with the siphunculus (MORE) or abdominal cuticle.

Rhinarium(s, rhinaria)

Secondary sensoria occurring on any of the third, fourth, and fifth segments of the antenna. See secondary sensorium.

Rostral

of or pertaining to the rostrum.

Rostrum(s, rostra) (Image)

A jointed sheath, extending beyond the clypeus, enclosing the stylets, composed of five segments, used for feeding.

Rudimentary gonapophysis (gonapophyses) (Image)

Reduced genitalia consisting of several seta-covered bumps in the hind region of an adult female.

Rugose

Roughened or bumpy. Opposite of smooth. See also scabrous.

S

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Scabrous (Image)

Extremely roughened and bumpy. Opposite of smooth. Usually used in reference to scabrous antennal tubercles. See also rugose.

Scape(s)

The first or basal segment of the antenna.

Sclerite(s)

A thickened and darkened region of the cuticle resembling a plate.

Scleroite(s) (Image)

A small sclerite restricted to and encircling the base of a single seta.

Sclerotization

A series or pattern of sclerites.

Sclerotized

Descriptive of the state of being hardened. Usually refers to a structure with thickened and darkened cuticle.

Sculpturing (Image)

Extensive series of small projections covering some or all of the body wall.

Secondary sensorium (sensoria)

Sensorium occurring on any of the third, fourth, and fifth segments of the antenna. See also rhinarium.

Secondary seta(e) (Image)

Seta between the basal and apical primary setae on the fourth rostral segment. Also known as accessory setae.

Segment(s)

One or more divisions in a larger structure. Segments in aphid morphology usually refer to the three segments of the thorax, the eight segments of the abdomen, the five or six segments of the antenna, the five segments of the rostrum, and the five or six segments of the leg. Note that a strict definition restricts "segments" to those divisions that are independently muscularized. Thus for example, the antenna would be considered to have only two true segments: the scape and the pedicel. The flagellum is divided into three or four non-muscularized flagellomeres. Likewise the tarsus is strictly composed of the two tarsomeres together as one segment and the tarsal claw as the second true tarsal segment. However, in common usage, the term "segment" is used for any division regardless of musculature.

Sensorium (sensoria)

Plate-like sensory organ of varying shape on any of the segments of the flagellum.

Seta(e) (Image)

A socketed, hairlike extension of the body wall. Setae are sometimes called hairs.

Setal

Of or pertaining to the seta.

Siphunculus (siphunculi) (Image)

Paired cylindrical chamber on the dorsal lateral surface of sixth abdominal segment from which alarm pheromones are expelled. See cornicle.

Spicule(s) (Image)

A small, sharp projection of the cuticle. See head spicules.

Spinal

Of or pertaining to the dorsal midline of the body.

Spiracle(s)

An external opening of the body wall opening into a trachea. Used for breathing.

Sternite(s)

A ventral sclerite, or subdivisions thereof.

Sternum(s, sterna)

The entire ventral aspect of the body.

Stigma(s,ta)

See pterostigma.

Stridulatory apparatus(es) (Image)

Sound producing organ consisting of a row of peg-like setae on the inner surfaces of the metatibiae and striations on the ventral lateral areas of abdominal segments 5 and 6.

Stylet(s)

Paired threadlike mouthparts used for piercing and transport of liquid nutrients into the body. When not in use, they lie partly within the sheath of the rostrum and partly coiled within the head. The coiled stylets of embryos are sometimes conspicuous within the parent abdomen.

Subapical

Of or pertaining to a position near to but just below or proximal to the apex.

T

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Tarsal

Of or pertaining to the tarsus.

Tarsal claw(s)

Curved, distally pointed, paired processes on the distal end of the last tarsal segment.

Tarsomere(s) (Image)

One of two "segments" of the tarsus, the basitarsus and distitarsus, but not including the tarsal claw.

Tarsus (tarsi) (Image)

The last two apical segments (tarsomeres) and tarsal claw of the leg.

Tergite(s)

A dorsal sclerite, or subdivisions thereof.

Tergum (terga)

The dorsal cuticle of the body.

Terminal

Of or pertaining to the last position (e.g., terminal antennal segment). See also ultimate and distal.

Thoracic

Pertaining or belonging to the thorax.  

Thorax(es, thoraces)

The three segmented middle region of the insect body, sometimes bearing 2 pairs of wings and always 3 pairs of legs. Divisible into the prothorax, mesothorax, and metathorax.

Tibia(s,e) (Image)

The fourth and longest segment of the leg basally attached to the femur and distally attached to the tarsus.

Tibial

Of or pertaining to the tibia.

Tibial peg(s) (Image)

A row of peglike setae on the inner surface of the metatibiae for stridulation. See rastral setae.

Trochanter(s) (Image)

The second segment of the insect leg basally attached to the coxa and distally attached to the femur. Rarely fused to and indistinguishable from the femur.

Trochanteral

Of or pertaining to the trochanter.

Trachea(s,e)

A tube within the aphid used to deliver oxygen. Tracheae open to the body wall at spiracles and extend and branch inward to reach each aphid cell.

Tracheal

Of or pertaining to the trachea.

Triommatidium (triommatidia) (Image)

A section of the compound eye, consisting of a cluster of three ommatidia, on each side of the head. In most adults, it is located on an ocular tubercle. Occasionally in apterae and immatures, the main part of the compound eye is absent and only the triommatidium is present.

Tubercle(s) (Image)

Projecting structure occurring on the surface of the cuticle. The functions of tubercles are varied, ranging from muscle attachment points to grasping points for ant mandibles. Marginal abdominal tubercles are important to aphid identification. The term "tubercle" can also refer to a protuberance of the head near the margin of the antennal socket: see antennal tubercle.

U

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Ultimate

Of or pertaining to the last position (e.g., ultimate rostral segment). See also terminal and distal.

Ultimate rostral segment(s) (Image)

The fourth and fifth rostral segments together. In many cases, the fifth segment is hard to distinguish, thus they are often measured together. Abbreviated URS.

Unguis (ungues)

In aphids, the processus terminalis. In most other insects, the unguis is the tarsal claw.

URS

Abbreviation for ultimate rostral segment.

V

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Vein(s)

Tubular structures supporting the connecting membranous areas of the wing.

Venter(s)

The lower aspect of the body, or the "belly" of the insect.

Ventral

Of or pertaining to the lower surface of the body or structure.

Vivipara(e) (Image)

A female adult capable of giving birth to nymphs through live birth. Contrasts with ovipara.

W

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Wax gland(s) (Image)

A cellular aggregate that secretes wax on the outer surfaces of the cuticle.

Wing(s)

One of four thoracic appendages used in aphid flight. Possessed by alatae (by definition). See also forewing and hindwing.

Wing pad(s)

One of four lobes in two pairs located on the pterothorax of a late-instar alatoid nymph. Wing pads are destined to become full wings when the individual molts to adulthood.

X

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Y

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Z

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