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Pemphigus populinigrae

Poplar-cudweed pouch gall aphid

Identification & Distribution  Other aphids on the same host 

Identification & Distribution

In spring, the fundatrices of Pemphigus populinigrae induce yellowish or dull reddish broad pouch-shaped galls (see first picture below), on the midrib of the upperside of leaves of poplar (mainly Populus nigra). Mature galls are rounded and smooth on top and are sometimes partially subdivided. (cf. Pemphigus gairi and Pemphigus phenax  which induce reddish elongate galls often tinged with yellow laterally). The galls of Pemphigus populinigrae are usually located near the middle of the leaf and open on the underside of the leaf (see second picture below). The fundatrices (not pictured) are green or greyish green, with 4-segmented antennae, which are about 0.17 times the length of the body. They have no siphunculi.

The winged migrants (see pictures below) from the primary host are dark green with a slight covering of powdery wax. Along the upper surface of the abdomen there are six rows of more-or-less fused wax-glands.

The six segmented antennae of the emigrant alatae (see pictures below) are about 0.3-0.4 times the length of the body, with a rather indistinct terminal process. Secondary rhinaria extend almost to the base of the third antennal segment, so that the small "tooth" on the inner side is distal to it. The third antenal segment has 12-18 secondary rhinaria, the fourth has 3-7 secondary rhinaria, the fifth has 4-7 secondary rhinaria, and the sixth has 4-7 secondary rhinaria (cf.Pemphigus populi  whose alatae have no secondary rhinaria on antennal segment VI). There is no brown shadowing around the wing veins. Siphunculi are present but small and indistinct.

Alatae of Pemphigus populinigrae emerge from the galls on poplar in June-August and migrate to found colonies above ground on the stems, leaves and flowers of cudweeds (Filago, Gnaphalium). Apterae on the secondary hosts are yellow-green, with white wax-wool. The adult body length is 2.0-2.2 mm. Sexuparae return in September-October to black poplar where the female oviparae lay overwintering eggs. Pemphigus populinigrae is found throughout Europe and across Asia to east Siberia.

 

Other aphids on same host:

Blackman & Eastop list 40 species of aphid  as feeding on Black, or Lombardy poplar (Populus nigra) worldwide, and provide formal identification keys.

Of those aphid species, Baker (2015)  lists 17 as occurring in Britain: Aulacorthum solani,  Chaitophorus leucomelas,  Chaitophorus populeti,  Chaitophorus populialbae,  Pemphigus bursarius,  Pemphigus gairi,  Pemphigus phenax, Pemphigus populi, Pemphigus populinigrae, Pemphigus protospirae,  Phloeomyzus passerinii, Pterocomma populeum,  Pterocomma tremulae,  Stomaphis longirostris, Thecabius affinis,  Thecabius lysimachiae and Tuberolachnus salignus. 

Acknowledgements

We have made provisional 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).

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