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Downy birch aphidIdentification & Distribution Biology & Ecology Other aphids on the same host
Identification & Distribution:Adult winged forms of Euceraphis punctipennis have a pale green abdomen and are covered with bluish-white wax. Their head and thorax are dark brown. Dorsal black patches when present are usually confined to abdominal tergites 4 and 5. Dark cross bands are never present in spring (distinguishes specimens from Euceraphis betulae, at least in spring!). The base of antennal segment VI is usually 1.33-1.75 times longer than the second hind tarsal segment (cf. Euceraphis betulae which has the base of antennal segment VI usually 0.8-1.32 times longer than the second hind tarsal segment). The body length of Euceraphis punctipennis adult alates is 3.0-4.8 mm.
The identity of the adult fundatrigeniae (see two pictures above) which are present mid-May-June, can also be determined by examining the pigmentation of the legs and antennae. Euceraphis punctipennis has the basal part of the fore tibia pigmented and scabrous for never more than quarter of total length (cf. Euceraphis betulae which has the basal part of the fore tibia pigmented & scabrous for at least one third of its length. Euceraphis punctipennis has the basal parts of antennal segments III and IV pale (cf. Euceraphis betulae which has the basal parts of antennal segments III and IV pigmented.). Immature Euceraphis betulae are green with conspicuous short black-tipped siphunculi.
The images below show Euceraphis punctipennis alates in alcohol, dorsal, and newly-moulted, lateral.
The downy birch aphid lives on the undersides of leaves of downy birch (Betula pubescens). Sexual forms occur in October and November. Euceraphis punctipennis occurs throughout Europe.
Biology & Ecology:
CytologyFemales of Euceraphis punctipennis have one pair of very long autosomes, two pairs of X-chromosomes and two B-chromosomes - that is 8 chromosomes in the normal diploid set (cf. Euceraphis betulae which has two pairs of autosomes, two pairs of X-chromosomes and two B-chromosomes - that is 10 chromosomes in the normal diploid set) (Blackman, 1977 ).
Host plantReviewing the literature on biology and ecology of Euceraphis punctipennis is problematical, due to the confusion in the literature pre-1977 of the silver-birch-feeding Euceraphis betulae with the downy-birch-feeding Euceraphis punctipennis. Although adult (winged) Euceraphis punctipennis may occur on either silver birch or downy birch (and many other trees and shrubs as accidentals), wingless forms (oviparae and immatures) are only known from downy birch (Betula pubescens) (Blackman, 1977 ). This leads to the conclusion that Euceraphis betulae feeds predominantly (only?) on silver birch, whilst Euceraphis punctipennis feeds predominantly (only?) on downy birch. Hence Mahdi & Whittaker (1993) found that, in two sites, 97% and 100% of Euceraphis feeding on Betula pendula were Euceraphis betulae. As far as we know, there has been no comparison of biology/ecology of these two species apart from establishing their different host plants.
Other aphids on same host:Blackman & Eastop list 15 species of aphid as feeding on downy birch (Betula pubescens) worldwide, and provide formal identification keys. Of those aphid species, Baker (2015) lists 14 as occurring in Britain: Betulaphis quadrituberculata, Calaphis betulicola, Calaphis flava, Callipterinella calliptera, Callipterinella minutissima, Callipterinella tuberculata, Clethrobius comes, Euceraphis punctipennis, Glyphina betulae, Glyphina pseudoschrankiana, Hamamelistes betulinus, Monaphis antennata, Stomaphis quercus and Symydobius oblongus.