Calaphis betulicola

Identification & Distribution:

Apterae of Calaphis betulicola (see first picture below) are pale green or yellowish, with dark apices to antennal segments, femoro-tibial joints, tibial apices and tarsi. The head and thorax are pale. The antennae are longer than the body, and the terminal process is clearly longer than the base of the last antennal segment. On Calaphis betulicola the secondary rhinaria are placed towards the middle of the segment (see second micrograph below) (cf. Calaphis flava which has the secondary rhinaria near the base of antennal segment III). The siphunculi are pale but with dark brown tips (cf. Calaphis flava which has the siphunculi pale or a little dusky at the flange). The body length of Calaphis betulicola is 2.0 to 2.3 mm.

Winged individuals (see second picture above) have characteristically darkened wing veins, and siphunculi with the apical halves dark brown to black. The micrographs below show (first) an adult apterous Calaphis betulicola in alcohol, and (second) the secondary rhinaria on antennal segment III placed towards the middle of the segment.

Calaphis betulicola is found on the undersides of leaves of range of Betula species, including Betula pendula and Betula pubescens, usually on seedlings and small trees less than 1 meter high. It has also been recorded as living on Betula nana in Scotland and Sweden. It is distributed from northern Europe across Russia to China and Japan, as well as in the USA and Canada.

Biology & Ecology:

We have found Calaphis betulicola in two areas in Britain - at Dundreggan in the Scottish Highlands, and at Selwyn Wood in East Sussex. At Dundreggan they were in very large numbers on young growth of Betula nana in a plant nursery and a polytunnel (see pictures below).

Some of the dwarf plants in the nursery had prematurely aged with bright red leaves, and they were similarly infested with Calaphis betulicola (see picture below).

Holman (1996) thought Calaphis betulicola was only a vagrant (accidental) on Betula nana, as he only observed adults on the plant. However, all stages were present in the populations we found on Betula nana, and they were clearly thriving, albeit under somewhat artificially favourable conditions.

Durak & Wojciechowski (2008) found that the eudominant species (comprising more than 10% in numbers) in Querco roboris-Pinetum mixed coniferous forest were Calaphis betulicola and Betulaphis quadrituberculata. For Calaphis betulicola an average of two peaks of occurrence were observed, one in the middle of May, the other in the middle of June. In the Leucobryo-Pinetum forest association an average of three peaks of Calaphis betulicola were observed - in the middle of May, in the middle of June, and in the middle of September.

Other aphids on same host:

• Blackman & Eastop list about 18 species of aphids as feeding on silver birch (Betula pendula) worldwide, and provides formal identification keys for aphids on Betula (Show World list). Of the species on Betula pendula, Baker (2015) lists 14 as occurring in Britain (Show British list).

• Blackman & Eastop list about 15 species of aphids as feeding on downy birch (Betula pubescens) worldwide, and provides formal identification keys for aphids on Betula (Show World list). Of the species on Betula pubescens, Baker (2015) lists 14 as occurring in Britain (Show British list).

• Blackman & Eastop list 11 species of aphid as feeding on Dwarf birch (Betula nana) worldwide (Show World list). Of those Baker (2015) lists 6 as occurring in Britain (Show British list).

Acknowledgements We especially thank Trees for Life for their kind assistance and support. Whilst we make every effort to ensure that identifications are correct, we cannot absolutely warranty their accuracy. We have mostly made identifications from high resolution photos of living specimens, along with host plant identity. In the great majority of cases, identifications have been confirmed by microscopic examination of preserved specimens. We have used the keys and species accounts of Blackman & Eastop (1994) and Blackman & Eastop (2006) supplemented with Blackman (1974), Stroyan (1977), Stroyan (1984), Blackman & Eastop (1984), Heie (1980-1995), Dixon & Thieme (2007) and Blackman (2010). We fully acknowledge these authors as the source for the (summarized) taxonomic information we have presented. Any errors in identification or information are ours alone, and we would be very grateful for any corrections. For assistance on the terms used for aphid morphology we suggest the figure provided by Blackman & Eastop (2006).

Useful weblinks

References  Durak, R. & Wojciechowski, W. (2008). Structure and dynamics of aphid communities connected with trees in selected forest associations. Polish Journal of Entomology 77, 79-92. Full text  Holman, J. (1996). Symydobius nanae sp. n. (Sternorrhyncha: Aphidoidea: Aphididae) and other aphids living on Betula nana in the Sumava National Park, Czech Republic. European Journal of Entomology 93, 239-248. Full text