Biology, images, analysis, design...
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Identification & Distribution:Apterae of Cinara pini are grey or greyish-green with black markings, and with either a slight bronze iridescence or a dusting of grey wax. The abdomen is wax powdered along the dorsal midline, along the segmental borders and laterally. The siphuncular cones are black and prominent. The body length is 1.9-3.7 mm (fundatrices larger).
The first picture shows an aptera and nymph of Cinara pini on Scots pine. The aptera is greyish-green with black markings, and has a slight bronzy iridescence. The wax powder along the dorsal midline is clearly shown. The ventral surfaces are mealy grey. Immatures are more greenish, have less patterning and have no mealy deposit. The alate viviparous female (see second picture) has more prominent wax deposits, and is generally more pigmented than the aptera (although not in the specimen below).
The two pictures above are micrographs of an aptera and alate of Cinara pini. Species identification of Cinara aphids on pine requires microscopic examnination because there are several rather similar species. One key distingishing feature of Cinara pini is that the length of the first tarsal segment (see first picture below) is less than 0.5 times the length of the second tarsal segment (distinguishes from the pine aphids Cinara schimitscheki and Cinara pinea). Also the length of the hairs on the hind tibia is less than 130um & those on the third antennal segment are less than 100um (distinguishes from Cinara pinihabitans).
The length of the two terminal segments of the rostrum of Cinara pini (see second picture above) is less than 1.2 times the length of the second tarsal segment and the hairs between siphunculi are short (distinguishes from Cinara acutirostris). Lastly the sclerotized part of the stylet groove (see second picture above) is 1.2-1.5 mm long and there are only 4 hairs on the antennal terminal process (distinguishes from Cinara nuda).
The oviparous female has no pericaudal wax ring and the male may be alate or apterous.
Cinara pini is found on young shoots of Scots pine (Pinus sylvestris) in spring, and later on the undersides of older foliated twigs or branches. The species overwinters as eggs. The oviparae (egg laying females) and males can be found in October. Cinara pini is found throughout Europe, also in Siberia and Japan, and introduced to North America.
Biology & Ecology:
The eggs are laid in lines of 2-5 eggs along the pine needles. These hatch in March and the emergent nymphs then feed on the bark of young branches or on growing shoots of young trees as can be seen in the two pictures below.
Larsson (1985) looked at the within-tree distribution of Cinara pini on Scots pine trees throughout the growing season. aphids were aggregated on the young internodes in the top parts of the crown during early summer, and on the older internodes in the lower parts of the crown during late summer. Seasonal changes in aphid distribution patterns were related to the changes which take place in the phloem sap of Scots pine during the course of the growing season.
All stages of this species tend to be highly variable (Fossel, 1972 ) both in markings and overall colour. The first picture above shows two of the main colour forms of the adult which range from an iridescent bronzy green to dark grey or almost black. The second image shows an adult aptera exuding a droplet of honeydew. Not surprisingly the Scots pine aphid is avidly attended by ants and is regarded as an obligate myrmecophile.
The first picture above shows southern wood ants tending a colony of Scots pine aphids. The second picture above shows a wood ant in full defensive posture. Bauer-Dubau (2000) studied populations of Cinara pini on Pinus spp. in a botanical garden in Berlin, Germany. It was the was the most common aphid species on Pinus spp. and was constantly and heavily attended by the ant Lasius fuliginosus, with up to 50 ants per colony. We have also noted the unusually large number of ants attending these aphids often with more ants than aphids! (see picture below) Bauer-Dubau found that the number of offspring produced by Cinara pini was higher when attended by ants. If it was not attended by ants, the anuses of the aphids become covered with honeydew and colonies dispersed.
Despite the near-ubiquitous presence of ants, colonies of Scots pine aphid are still attacked by natural enemies, especially aphid parasitoids. Slawinska & Jaskiewicz (2005) found a range of predators present in Lublin, but felt that numbers were too low to have much impact on aphid numbers. Only one primary parasitoid (Pauesia picta) was present, although there were several species of hyperparasites. We have found several parasitoid mummies one of which is shown in the picture below. This also proved to be a Pauesia species as shown in the second picture below.
Völkl & Kroupa (1997) looked at the effects of adult mortality risks on parasitoid foraging tactics. When searching on Scots pines, females of the aphid parasitoid Pauesia silvestris foraged more successfully on the pine aphid Cinara pini than on Cinara pinea. However, the parasitoids suffered from a high mortality (19.5%) from ant aggression when foraging for Cinara pini while mortality was zero on pines with C. pinea. All females that were killed were foraging on the bark, while females searching on needles were safe from ant attacks. When searching for Cinara pinea the parasitoid spent significantly more time on needles if the aphid colonies were ant-attended. On pines with Cinara pini in contrast, females spent more time on bark in ant-attended colonies. The high adult mortality risk on bark was counterbalanced by a significantly higher foraging success in ant-attended colonies.
Damage and control
No detailed work has been done on the effect of Cinara pini on pine but there are few visible signs of damage. Nevertheless Jaskiewicz (2005) suggests that heavy infestations can lead to a general weakening of the plant. However, aphid infestations benefit honey producers since bees feed on the aphid honeydew.