Morphological terms

This page is under development. Definitions will also eventually link to figures.

Alphabetic index: :
anal plate, antenna, basitarsus, cauda, compound eye, cornicle, costa, costal vein, coxa, cubital vein, cubitus, distitarsus, dorsal tubercle, femur, flagellomere, flagellum, frons, genital plate, gonapophyses, gonochaetae, lateral ocellus, lateral tubercle, leg, longitudinal vein, medial vein, median ocellus, medius, ocellus, ocular tubercle, ommatidion, pedicel, pretarsal setae, pretarsus, processus terminalis, siphunculus, pterostigma, radial sector, radial vein, radius, rhinarium, scape, stigma, tarsus, terminal process, tibia, triommatidion, trochanter, tubercle, unguis, wax plate

Structural groups:
head, antenna, thorax, leg, forewing, abdomen.

Descriptive adjectives: [to follow]

Structural Groups:

Front part of head capsule above mouthparts and between antennal bases; in aphids a small triangular area, usually poorly delimited. In winged forms, it bears the median ocellus.
the first antennal segment
the second antennal segment
Flagellum, flagellomeres
the remainder of the antenna. Technically a single subdivided segment, in aphids consisting of 1 to 4 articles or flagellomeres (usually 4).
processus terminalis
a thin filamentous process appended to the end of the distal flagellomere. (Also called unguis, historically sometimes referred to as the spur).
Rhinarium [-a]
Membranous sensory areas on the antenna.
Compound eye
Large image-forming eye at side of head consisting of numerous facets or ommatidia.
Triommatidion, triommatidium, ocular tubercle
A group of three eye facets, often set on a rounded protuberance, located on the posteroventral margin of the compound eye. If the compound eye is absent, the triommatidion is still always present. In some species with a well developed compound eye, the triommatidion is not apparent.
Ocellus [-i]
One of three light-sensitive organs, two on the top of the head between the compound eyes (lateral ocelli), and one on the frons (median ocellus). In aphids, present only in winged forms (and some intermediates).
The basal leg segment, articulating with the body wall. In aphids rather broad based.
The second leg segment, usually quite small. In aphids not subdivided.
The third leg segment; the first major segment.
The fourth leg segment; the second major segment.
The fifth leg segment, usually subdivided: the 'foot'. In aphids with two articles when normally developed. Rarely the two are partly fused, or one or both is missing.
The basal tarsal article. In aphids short, usually triangular, or trapezoidal with the dorsal surface noticeably shorter than the ventral surface.
The distal tarsal article.
the small distal leg part, consisting of the claws and associated minute sclerites. In aphids, with 2 claws, an unguitractor plate, and a small ventral sclerite articulating with the unguitractor plate, bearing 2 setae (the pretarsal setae).
Pretarsal setae
A pair of seta-like structures on a small sclerite on the underside of the pretarsus between the bases of the claws. Also know as 'plantar setae', 'empodia', 'empodial setae', 'arolia' or 'claw setae'.
Common longitudinal vein
The subcostal vein and the basal parts of the radius, medius and cubitus of the forewing of an aphid are concentrated toward the anterior part of the wing and fused into a common longitudinal vein parallel to the costal margin. The tracheal traces of the component veins remain independent within the common structure.
Anal vein
Veins of the postero-basal angle of the wing; in aphids essentially absent, although the posterior cubital branch is sometimes called the anal vein.
Costa, costal vein
Vein along the anterior margin of the wing.
Cubitus, cubital vein
Veins of the posterior part of the wing; in aphids with two branches. However, in most aphids, the branching point is within the common longitudinal vein, thus appearing as two separate transverse veins in the basal half of the wing.
Medius, medial vein
vein of the central area of the wing; in aphids, extending from the longitudinal just before the base of the pterostigma, extending to the posterodistal margin of the wing. Usually twice branched (.i.e. three branches reaching the wing margin), but often once branched or unbranched. Absent in Phylloxeroidea.
Radius, radial vein
Vein of the anterior part of the wing; in aphids, the free parts represented by the pterosigma and radial sector.
Radial sector
Curved vein, in aphids arising from the posterior margin of the pterostigma.
Pterostigma, stigma
Broad, thickened part of radial vein in the distal part of the anterior wing margin.
Abdomen: [figure]
A dorsolateral valved opening on the posterior part of the abdomen, usually elevated on a conical to tubular projection. Unique to the Aphidoidea. When alarmed, an aphid secretes an oily substance which hardens on contact with the air; the secretion apparently also contains alarm pheromones. Also called cornicle; historically "honey tube".
Anal plate
A sclerotized area with strongly denticulate or spinulose sculpture situated in front of the anal opening. Present in both larvae and adults of both sexes. (In adult females, the genital opening is in front of the anal plate.)
Genital plate
A sclerotized area in front of the genital opening of adult females (both parthenogenetic and sexual forms).
Two to four dense clusters of short setae on the anterior margin of the genital opening of adult female aphids (both parthenogenetic and sexual forms) (behind the genital plate). Used to anchor the embryo or egg during birthing. The clusters are often called 'gonapophyses'.
A modified ninth abdominal tergite, with strongly spinulose sculpturing and often with several long curved setae, situated above the anal opening. Together with the anal plate, serves to localized honeydew droplets from the anus and prevent fouling of the body. In many aphids, the cauda is long and mobile, and is used to flick the droplet away. In ant-tended aphids, the cauda is usually short and rounded and helps hold the droplet until collected by the ants.
Lateral & dorsal tubercles
Thin walled cuticular structures, usually protuberant, sometimes flat. May be present on lateral margin of thoracic and abdominal segments, and submedially on dorsum of head, prothorax (rarely on other thoracic segments), and abdominal segments. Function unknown.

Aphids of British Columbia: last update 1998-10-05
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