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Currant - daisy aphidsOn this page: Genus Nasonovia Nasonovia compositellae Nasonovia pilosellae Nasonovia ribisnigri
Nasonovia are medium-sized green or reddish, rather shiny aphids with a well-marked dorsal sclerotic pattern of pigmented paired intersegmental muscle plates. Adult viviparae may be winged or wingless. There are distinct antennal and median tubercles and the antennae are rather long. The siphunculi are cylindrical and rather long, with little or no apical reticulation The cauda is elongate and rather blunt finger-shaped.
There are about 30-45 Nasonovia species worldwide, which host alternate between currants (Grossulariaceae) and various daisies (Asteraceae), among which the most important are lettuce (Lactuca), Crepis and various species of Hieracium. They are not attended by ants. One species, Nasonovia ribisnigri, is an important and cosmopolitan pest of lettuce.
Nasonovia compositellae (Black-backed daisy aphid)
The adult aptera of Nasonovia compositellae has a black head, and black cross bars across the pronotum and mesonotum. There is an extensive shining black dorsal abdominal shield covering the metanotum and abdominal tergites 1-VI , and tergites VII and VIII with black cross bars (see pictures below) (cf. Nasonovia ribisnigri and Nasonovia pilosellae which have no black dorsal abdominal shield, but only dark intersegmental sclerites between each abdominal segment). The body is dark green, often (as here) strongly tinged with orange-red. The antennae are 0.8-0.9 times the body length. The siphunculi are thick at the base and 1.3-1.6 times the length of the cauda. The cauda is finger-shaped with 7 hairs. The body length of the Nasonovia compositellae adult aptera is 1.8-2.5 mm.
There are two subspecies of Nasonovia compositellae:
Nasonovia compositellae feeds on hawkweeds (Hieracium species). In spring it feeds on the upper sides of the leaves which fold upwards to enclose the colonies, and later colonizing stems and flowers. Nasonovia compositellae subspecies compositellae produces sexuales in autumn and overwinters as eggs. It is found in the north and west of England and in Wales, Scotland and Ireland. Outside Britain it is only known from Norway and Iceland, so it is a true northern subspecies. Nasonovia compositellae ssp. nigra mainly overwinters as parthenogenetic viviparae. It is found in southern England and Wales, and is widely distributed in Europe.
Nasonovia pilosellae (Hawkweed aphid)
Adult apterae of Nasonovia pilosellae are medium-sized yellowish-green to blackish, rather shiny aphids. There are dark intersegmental sclerites between each abdominal segment, as well as variable and usually ill-defined dorsal pigmentation of the abdomen. The ratio of the length of the terminal process of the last antennal segment to its base ranges from 5.7-8.0 (cf. Nasonovia ribisnigri in which the ratio of the length of the terminal process of the last antennal segment to its base ranges from 7.0-11.4). The secondary rhinaria on the third antennal segment spread out along one side of the segment (see micrograph below) (cf.Nasonovia ribisnigri where the secondary rhinaria on the third antennal segment tend to be concentrated on the basal part of the segment). The first segment of their hind tarsus has two hairs. Their siphunculi are cylindrical and rather long, with little or no apical reticulation The cauda of Nasonovia pilosellae is elongate and rather blunt finger-shaped. The body length of the Nasonovia pilosellae adult aptera is 1.2-2.5 mm.
The alate (see second picture above) has a green abdomen with black marginal sclerites. The dark green spino-pleural markings are variably developed.
The hawkweed aphid lives all year round on a few related species of hawkweed, namely the orange hawkweed (Pilosella aurantiaca), common hawkweed (Hieracium lachenalii) and the mouse-ear hawkweed (Hieracium pilosella).
Nasonovia ribisnigri (Currant-lettuce aphid)
Nasonovia ribisnigri apterae on the primary host (gooseberry and blackcurrant, see first picture below) are shiny green with no dark markings. On their secondary host (various members of the daisy family) Nasonovia ribisnigri apterae are more variable in colour, ranging from green to yellow or pink, and have dark intersegmental sclerites between each abdominal segment (see second picture below). The length of the terminal process is 7.0-11.4 times the length of the base of the antennal segment VI (cf. Nasonovia pilosellae which has the length of the terminal process 3.4-8.3 times longer than the base). The first segment of the hind tarsus has three hairs. Nasonovia ribisnigri siphunculi are pale with dark tips. They are at least as long or longer than the cauda and taper slightly. The cauda is finger shaped, not constricted and the same colour as the basal part of the siphunculi. The body length of Nasonovia ribisnigri apterae is 1.3-2.7 mm.
Alate Nasonovia ribisnigri (see third picture above) have a conspicuous pattern of black abdominal markings. They have 23-66 secondary rhinaria on the third antennal segment, 2-14 on the fourth segment and none on the fifth segment.
The currant-lettuce aphid host alternates from currants (Ribes spp.), especially gooseberry and blackcurrant, to various Asteraceae, including lettuce, as well as Brassicaceae, Scrophulariaceae and Solanaceae. Nasonovia ribisnigri is found throughout Britain and continental Europe east to Ukraine, and has been introduced to North and South America.