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Black-stem aphidOn this page: Identification & Distribution Biology & Ecology: Life cycle Colour Ant attendance Natural enemies Other aphids on the same host Damage & Control
Identification & Distribution:
Apterae of Cinara confinis are greenish-black (see first picture below) or dark brown, with a double row of blackish slightly shining speckles and small flecks of fine wax in transverse rows. The head and thoracic plates are dark brown, with some wax markings on the thoracic plates. The length of the sclerotized part of the stylet groove is greater than 1.8 mm. The antennae of Cinara confinis are pale yellowish-grey with a darkening of each segment distally. The length of the fifth antennal segment, including the terminal process, is clearly longer than the fourth antennal segment. The tibiae are only slightly bowed (cf. Cinara curvipes in which the tibiae are noticeably long and bowed). The femora and tibia either have dark brown annulations or are mainly black, and the tarsi are black. The siphuncular cones are dark and prominent (cf. Cinara pectinatae which has small pale siphunculi). The body length is 3.8-7.8 mm
Cinara confinis alatae (see second picture above) are grey-green also with small flecks of fine wax in transverse rows, and some wax markings apparently extending on to the anterior abdominal tergites. The ovipara is similar to the vivipara apart from having numerous pseudosensoria on the hind tibiae; it has no posterior wax ring.
Cinara confinis feeds on the stems and twigs, rarely on the roots, of many fir (Abies) species, and sometimes on Himalayan cedar (Cedrus deodora). It has a holarctic distribution and is recorded from Europe, much of Asia, North America (formerly known as Cinara grossa) and Argentina. Carter & Maslen (1982) describe it as of sporadic occurrence in Britain occurring in northern Scotland, west of Ireland and southern England.
Biology & Ecology:
Struble et al. (1976) describe the biology of Cinara confinis (under the name Cinara abieticola) in Maine, USA. Fundatrices were first found in May at the bases of buds. Resultant colonies were generally located on the trunk just below the first whorl of branches, as shown in the picture below for a colony in Sussex, UK.
Parthenogenetic reproduction combined with viviparity means that colonies can build up rapidly.
Colonies can reach an enormous size especially on trees in urban areas where natural predators are lacking.
Colonies disperse rapidly if disturbed. Apterous females tend to drop off but nymphs move rapidly up or down the stem and on to the branches. The picture below shows a dispersing nymph moving away from a disturbed colony.
In Maine, colonies on fir trunks declined by mid June as aphids moved to root collar and roots. Movement to tree roots in summer has only rarely been recorded in Britain (Carter & Maslen (1982)). Winged males and oviparae can be found in October, and the aphid overwinters in the egg stage.
Cinara confinis is one of a number of aphid species which has (apparently) aposematic coloration in the adults, but cryptic coloration in the nymphs (see also aphid color). The first picture below shows a metallic dark green adult aptera of Cinara confinis patterned with white wax.
The green sheen is sometimes much less in evidence, and the adult is instead dark brown (see picture below).
We have found a single alate which was cryptically coloured, varying from grey to grey green with white wax markings (see picture below).
Immatures are cryptically coloured with classic disruptive camouflage (see picture below).
Binazzi & Scheurer (2009) report that Cinara confinis is optionally dependent on ant attendance. This species sometimes occurs in special earth galleries constructed by ants on the bark of fir trees (Wood-Baker, C., 1964). All the colonies we have found have been strongly attended, mostly by southern wood ants (Formica rufa).
In 2018 we found colonies of Cinara confinis on young Abies trees attended not by Formica rufa, but instead by Lasius fuliginosus (see picture below).
On one occasion several of the colony had been parasitized despite the presence of ants. The resultant aphid mummies were blue-black and two are shown below along with a live unparasitized adult.
The adult parasitoid is shown below (first), with an enlargement of the head and antennae (second).
Given the extraordinary number of antennal segments (Baker, pers. comm.), this parasitoid is almost certainly Pauesia grossa. This species is a parasitoid specific to Cinara confinis, but it has not been previously recorded in UK. Few predators have been observed around Cinara confinis colonies, although Struble et al. (1976) reported larvae of Metasyrphus medius in June.
Other aphids on same host:
Damage and control
Although Cinara confinis is still rare in Britain, it can occur in enormous numbers on large fir and cedar trees grown for their amenity value in urban areas of the USA. With large infestations, the tendency of the aphids to wander about a lot means they can cause a public nuisance - which is accentuated by the honeydew deposits, sooty moulds and abundant wasps.
The image above is of an Abies amabilis (Pacific silver fir) found infested with Cinara confinis at Bedgebury Pinetum, UK.