Biology, images, analysis, design...
|"It has long been an axiom of mine that the little things are infinitely the most important" |
Green-striped fir aphidOn this page: Identification & Distribution Biology & Ecology: Colour Ant attendance Population dynamics Other aphids on the same host Damage & Control
Identification & Distribution:
Apterae of Cinara pectinatae are large and (usually) the abdomen is shiny bright olive green, with three diffuse paler green longitudinal bands (see first picture below). There is also a brown form (see second picture below). The head and appendages are brown and the eyes are red. The abdomen has numerous small spots scattered over the entire dorsum. The siphuncular cones are small and pale. The legs are pale and spotted or mottled with brownish. The first hind tarsal segment is at least half as long as the second hind tarsal segment. The Cinara pectinatae apterae body length is 2.8 to 5.0 mm.
The micrographs below show dorsal views of the aptera, green and brown forms, in alcohol.
Cinara pectinatae feeds on firs (Abies species), especially Abies alba (silver fir) but also Abies nephrolepis, numidica, pindrow, sutchuenensis (= Abies fargesii var. sutchuenensis) and veitchii. Oviparae and alate males are found in October. It is not recorded from any North American firs. Cinara pectinatae occurs throughout Europe eastward to Turkey.
Biology & Ecology:
The green-striped fir aphid is a solitary species which lives singly on small branches where it feeds at the junction of petiole and stem as shown below.
Cinara pectinatae do not move very much, and are well anchored by means of their strong claws. They rely on cryptic colouration with the green form resembling the green needles to protect them from (avian ??) predators. We have also found a brown female morph on two species of fir (Abies veitchii and Abies procera). The published literature states that only male Cinara pectinatae are brown. The brown form of the female closely matches the colour of the buds and the stem (see picture below).
The brown females are morphologically identical to the usual green form. As with the green form, the siphuncular cones are small and pale (see below first) and the first hind tarsal segment is at least half as long as the second hind tarsal segment (see below second).
We have recently been informed by Andrea Binazzi that he does recall brown forms of Cinara pectinatae morphologically identical to the green forms appeared in Tuscany, in late summer and autumn (see full comments below by Andrea Binazzi and Stephan Scheurer).
The presence of Cinara pectinatae on tree foliage is often betrayed by the activities of wasps and ants. Lehr (1988) confirms that Cinara pectinatae is ant attended, although there are rather few reports in the literature about which species attend. We have found Lasius fuliginosus on fir branches occupied by Cinara pectinatae and (eventually) observed them to be actively tending them (see picture below).
However, Lasius fuliginosus are unusually sensitive to disturbance when attending Cinara pectinatae, and both aphids and ants leave the scene very rapidly if disturbed.
As well as actively tending the aphids to stimulate honeydew production, Lasius also appears to glean honeydew droplets from the needles and from the ground (see picture above).
The population dynamics of Cinara pectinatae have been studied in both France and Germany because it is a copious honeydew-producer, important to forest bee-keepers in Central Europe. In a seven year study, Maquelin (1974) found that the number of eggs laid in autumn was inversely related to peak numbers in summer. Bloc et al. (1984) monitored populations in France over two years. They concluded that rainfall was an important factor affecting numbers. When rainfall was heavy during the development of the first virginoparae generations, it prevented Cinara pectinatae populations from reaching high levels. This in turn reduced honeydew production and a prevented a heavy 'fir honey' harvest by bees.
In Germany Liebig et al. (1982) monitored populations over four years They found there were 4 or 5 phases in the population trends from March till October.
Liebig concluded that variations in population size were not caused by rainfall and changes of temperature. Instead the fertility and mortality of Cinara pectinatae was influenced by the physiological state of the host-plant.
In southern Germany Cinara pectinatae is the most important honeydew-producing aphid feeding on white fir (Abies alba). Liebig (1987) investigated the population dynamics of the species to determine the factors affecting honey flow from white fir. The fir plantations were suffering from a disease, so it was of interest whether this disease affected the population dynamics of Cinara pectinatae. Typical population trends included a population increase during sprouting of trees in May, June and July, to give a peak in July /August and a collapse of the populations afterwards in August and September. In heavily diseased fir plantations there was a second peak of population density in September, caused by intensive reproduction in the late summer.
We have not observed any natural enemies attacking Cinara pectinatae in UK, but Stary (1976) records that it is parasitized by Pauesia infulata.
Other aphids on same host:
Blackman & Eastop list 15 species of aphid as feeding on silver fir (Abies alba) worldwide, and provide formal identification keys (Show World list). Of those aphid species, Baker (2015) lists 8 as occurring in Britain (Show British list).
Damage and control
There are no reports of Cinara pectinatae causing damage to fir trees, and in central Europe they are considered beneficial for honey production.