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Mealy Spruce AphidOn this page: Identification & Distribution Biology & Ecology: Life cycle Ant attendance Natural enemies Other aphids on the same host Damage & Control
Identification & Distribution:
Cinara costata apterae are usually wax-covered; young adults have characteristic sausage-shaped rings of wax on the dorsal cuticle (see first picture below). Under the wax they are light brown or yellow-brown, sometimes with a dull metallic golden sheen, and with a pair of wax-covered dark bottle-green dorsal longitudinal stripes which sometimes coalesce at about the level of the siphuncular cones. The rather uniform yellow-brown ground colour is good identification characteristic for unwaxed colonies. The terminal rostral segments (R IV+V) are longer than the second segment of the hind tarsus (HTII), and HTII is shorter than maximum diameter of the large dark prominent siphuncular cones (cf. Cinara pilicornis which has R IV+V shorter than HTII, and HTII is longer than the maximum diameter of the small, rather pale siphuncular cones). The prominent siphuncular cones are dark brown and usually spaced three or more diameters apart (cf. Cinara pruinosa which has the prominent blackish siphuncular cones two diameters or less apart). The body length of adult Cinara costata apterae is 2.7-3.8 mm.
Both images above copyright Anders Albrecht under a Creative Commons Attribution 3.0 Unported License.
Cinara costata alatae have characteristically pigmented forewings with a dark area near the apex and another one near the middle of the posterior border of the wing. The medial vein is only once-branched. The oviparae have their hind tibiae thickened with numerous pseudosensoria.
The mealy spruce aphid forms small colonies (see second picture above) on smaller woody twigs on lower branches of Spruces (Picea species). These twigs also receive a deposit of mealy wax and the aphids are not usually attended by ants. Oviparae and males occur in the northern hemisphere in October. Cinara costata occurs in Europe, east Asia, Australia, Greenland, Canada and USA.
Biology & Ecology:
Núñez-Pérez & Tizado (1996) recorded Cinara costata as living on the oldest branches or on the trunk when the tree is young, and forming dense floury looking colonies on branches because of its wax covering. The colony below had heavy wax powdering of all the colony.
The picture below shows a group of fourth instar nymphs.
The picture below shows an adult aptera from the unattended colony.
Note especially the characteristic sausage-shaped rings of wax on the dorsal cuticle of the adult.
Although Cinara costata produces abundant honeydew, it is not generally ant-attended - unlike most Cinara species. Binazzi & Scheurer (2009) give the species as independent from ant attendance. We have nevertheless found it attended by wood ants on one occasion (see image below).
It was notable that, contrary to the normal situation, these Cinara costata were largely unwaxed, and had no wax dorsally.
Since the immatures from this ant-attended colony were so atypical, to check identification we tried rearing them through to adults - minus the accompanying ants. The resulting adult (shown below) developed the wax patterning 'typical' of Cinara costata, but with unusually small separation of the siphuncular cones. This small separation led to us misidentifying this colony as Cinara pruinosa for an extended period of time. We suspect this was because the specimen was reared from the third instar stage on a small spruce cutting in water, leading to it being very undersized. This is known to affect not only absolute measurements, but some of the ratios so widely used in aphid identification.
This would imply that the wax is primarily for defense against predators, with unwaxed colonies being defended by the ants. The lack of wax when ant-attended suggests that either (1) Cinara costata only develops its wax coating if it is not being attended, or (2) that if they happen to become ant-attended, the ants remove any wax coating (which seems unlikely given the unpalatable nature of wax).
Where Cinara costata was attended by ants we observed neither predators nor parasites. Where it was unattended we found potential predators present near the aphid colonies - specifically of the larch ladybird (Aphidecta obliterata) shown below.
When Aphidecta was introduced to a branch with Cinara costata, it rapidly started devouring them. This does not prove this coccinellid is an important or frequent predator, but it certainly shows that it will eat unattended Cinara costata colonies when hungry!
Other aphids on same host:
Cinara costata has been recorded on 14 Picea species.
Damage and control
Delfino and Binazzi (2002) list Cinara costata as one of many aphid species causing economic damage to conifers in Argentina. Larsson & Björkmanan (1993) found there was no significant difference in the build-up of mealy spruce aphid densities between drought-stressed and unstressed spruce trees. This is in contrast to most other stress experiments, which have demonstrated enhanced performance of phloem-feeding insects on drought stressed trees.