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Genus Pemphigus [Macrosiphini]

Small to medium-sized yellowish-green or greyish-green aphids which cause galls on the leaves, petioles or branches of the primary host. The fundatrices have spinal, pleural and marginal wax glands on most body segments. The winged viviparous females that develop in the galls have a black head and thorax and have the abdomen dusted in wax.

The primary host of Pemphigus species is Populus (poplar) where they are not attended by ants. Secondary hosts include Asteraceae and Apiaceae, whilst some species remain on one host all year.

 

Pemphigus bursarius (Poplar-lettuce gall aphid)

In spring, aphids form yellowish or reddish pouch-shaped galls (see picture below) on the petioles of the leaves of poplar. There may be more than one gall per petiole and the leaf lamina may curl and yellow.

The developing fundatrix in the gall is green with brown head and legs, wax covered and has no siphunculi. The 4-segmented antennae are about 0.12-0.15 times the length of the body.

 

The winged viviparae that emerge from these galls (shown live, and in alcohol, above) are greyish-green or greyish-brown with small siphuncular pores and are lightly covered with wax powder. Their antennae are 0.33-0.4 times the length of the body and have a distinct terminal process. There is brown shadowing around the wing veins.

This species host alternates between poplar and members of the daisy family Asteraceae, especially lettuce. In summer they live on the roots of the secondary host. The picture below shows a developing alate living on the roots of lettuce.

It can be a serious pest of lettuce. Its distribution is almost cosmopolitan being found in Europe, western and central Asia, the Americas, northern and southern Africa and (possibly) Australia and New Zealand.

 

Pemphigus gairi (Poplar pouch gall aphid)

In spring aphids form yellowish or reddish pouch-shaped galls (see picture below) on or near the midrib of the leaves of poplar, mainly black poplar (Populus nigra).

The developing fundatrix in the gall is covered with wax (first picture below). We removed the wax from the one in the second picture below to show distinguishing features. The fundatrix is green or greyish green and has no siphunculi. The 4-segmented antennae are about 0.12-0.15 times the length of the body.

 

The winged viviparae (see below) emerge from these galls in summer through an opening on the underside of the leaf. They have a black head and pterothorax, small siphunculi and a rather elongate greenish wax-dusted abdomen. The fused terminal segments of the rostrum are 0.07-0.10 mm long, usually less than 0.55 the second hind tarsal segment. The third antennal segment is shorter than the combined length of fourth and fifth antennal segments.

Apterae on secondary hosts are yellow-green with white wax wool.

This species host alternates between poplar and fool's parsley (Aethusa cynapium). In summer they live above ground on the secondary host, often in the inflorescences. Distributed throughout Europe and into Asia and north Africa.

 

Pemphigus protospirae (Poplar polyspiral gall aphid)

In spring, aphids form green or green mottled with red smooth galls formed by thickening, flattening and spiral twisting of the leaf petiole of Populus nigra on the petioles of the leaves of poplar. The fundatrices have antennae about 0.2 × the length of the body and lack siphunculi.

All the second generation aphids are winged and leave during late spring to early summer. The winged migrants are greyish-green and lightly covered with waxy powder. The antennae are 0.33 - 0.40 times the length of the body. The most proximal rhinarium on third antennal segment is distal to the tooth. The number of secondary rhinaria on the third antennal segment is 10-14, on the fourth 2-5, on the fifth 2-4, and on the base of the sixth 2-8.

The winged migrants move to aquatic umbellifers (Apiaceae) as secondary hosts.

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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