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One of a pair of tubular organs on the abdomen of an aphid, from which the insect secretes a waxy fluid when attacked.

[Latin corniculum, little horn; see corniculate.]


a wax-secreting organ on an aphid's abdomen that is shaped like a horn
References in periodicals archive ?
Alatae, produced in the second and third generations, are grayish-green with a black head and thorax, dark antennae, legs and siphunculi and a large quadrate dark green patch on the dorsal abdomen; they migrate to various Polygonum and Persicaria spp.
Mummies were black in color each with an emergence hole usually at dorsum above the siphunculi (Plates V and VI; Suppl.
Wahlgreniella nervata (Gillette 1908) is a spindle-shaped, pale green aphid characterized by elongate swollen siphunculi, apterae without sensoria on third antennal segment, cauda bearing five hairs and well developed lateral frontal tubercles (Heie 1986).
The comparative morphological study was conducted on species (i) whose apterae possess swollen siphunculi and have been recorded in North America or (ii) are known to feed on Asteroideae species over the World.
Body is small and brown with dark siphunculi and the cauda unusually long and pale.
Distinguishing characters of the Lachninae include: (1) anal plate whole, (2) cauda broadly rounded or arc-shaped, (3) processus terminalis of antennal segment VI noticeably shorter than base of this segment, (4) ultimate rostral segment with 2 clearly differentiated portions, (5) head bearing an epicranial suture is well separated from prothorax, (6) empodial setae short and fine, (7) secondary sensoria subcircular or slightly ovoid, (8) antennae usually shorter than body (slightly longer than the body in some species), and (9) siphunculi troncoconic, short and robust (more or less volcano-like) with associated setae, or small at distal ring (poriform).
The classical separation of the subgenera Uroleucon, Uromelan and Lambersius is based on the pigmentation of the siphunculi and cauda (considered separately and compared), and secondly on the color of the body when alive and the dorsal sclerites of the abdomen; also, Lambersius is restricted to America, except for certain anthropic introductions.
6 mm) and are characterized by their natural dark coloration, white capitate setae, dark cauda, and the bicolored siphunculi (Figs.
The alatae viviparous females are more long-bodied and have longer siphunculi than the apterous ones.
Morphologically, the genus Aulacorthum is well characterized by "head with well developed antennal tubercles, inner sides of tubercles nearly parallel; median tubercle on frons hardly developed; head usually granulate in apterous; first tarsal chaetotaxy 3:3:3; siphunculi cylindrical, or slightly swollen, normally broad at base, rather long with usually a few row of flat hexagonal cells at apex under broad distal flange; cauda tongue-shaped with 4-8 setae, mostly 7 setae.
cuschensis because (1) membranous distal part of the caudal knob in apterous viviparous females is small, contrasting very little with the rest of the knob; (2) the dorsum of head, antennae, legs, and siphunculi are very weakly pigmented in apterous viviparous females; (3) setiferous sclerites are absent from dorsum of abdomen in apterous viviparous females; and (4) they are green when alive.
Ortego) collected a sample of aphids belonging to tribe Macrosiphini (Aphididae) and to the group of Macrosiphum Passerini, 1860, and related genera, which is characterized by the reticulated ornamentation on the distal part of siphunculi.