InfluentialPoints.com
Biology, images, analysis, design...
Aphids Find them How to ID AphidBlog
"It has long been an axiom of mine that the little things are infinitely the most important" (Sherlock Holmes)

 

 

Genus Pemphigus [Pemphigini]

Pemphigus are small to medium-sized yellowish-green or greyish-green aphids which cause galls on the leaves, petioles or branches of their 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. Their secondary hosts include Asteraceae and Apiaceae, whilst some Pemphigus species remain on one host all year.

 

Pemphigus bursarius (Poplar-lettuce gall aphid)

In spring, Pemphigus bursarius form yellowish or reddish pouch-shaped galls (see first picture below) on the petioles of the leaves of their primary host, poplar (mainly Populus nigra). There may be more than one gall per petiole and the leaf lamina may curl and yellow. Inside the gall the developing Pemphigus bursarius fundatrix is green with brown head and legs, wax covered and has no siphunculi. The 4-segmented antennae of the mature fundatrix are about 0.12-0.15 times the length of the body. The fundatrix then produces large numbers of alate offspring (see second picture below) which leave the gall in late May.

The winged viviparae (see micrographs below) that emerge from these galls are greyish-green or greyish-brown with small siphuncular pores and are lightly covered with wax powder. There is brown shadowing around the wing veins. Their antennae are 0.33-0.4 times the length of the body and have a distinct terminal process. When the antennae are 6-segmented, the third antennal segment is 2.09-2.65 times longer than the fourth antennal segment (cf. Pemphigus gairi where the the third antennal segment is 1.53-2.00 times longer than the fourth antennal segment).

Pemphigus bursarius host alternates between poplar and members of the daisy family (Asteraceae), especially lettuce. In summer they live on the roots of the secondary host where they 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.

Read more...

 

Pemphigus phenax & Pemphigus gairi (Poplar pouch gall aphids)

In spring Pemphigus phenax and Pemphigus gairiform yellowish or reddish elongate pouch-shaped galls on black poplar (Populus nigra) (see first picture below). The galls are usually more or less in the middle of a leaf, and are on or near the midrib. The slit-like opening on the underside extends over the entire length of the gall. (cf. Pemphigus populinigrae which induce broader pouch-shaped galls with the opening extending over part of the gall).

  • Galls of Pemphigus gairi are rather thin walled, slightly shining, green-yellow in colour and only rarely slightly reddish. The swelling is nowhere more than four times the normal thickness.
  • Galls of Pemphigus phenax have a slightly wrinkled surface, more or less red in colour and often with yellow sides. The swelling is over five times the normal thickness .

Given the features above (colour and thickness) the gall below would appear to be Pemphigus phenax. Note however, that some authorities (e.g. Blackman) believe that the galls of these two species are too similar to differentiate. Inside the gall the developing Pemphigus fundatrix is dull green or greyish green, and is covered with wax. The 4-segmented antennae are about 0.12-0.15 times the body length.

The offspring of the fundatrix develop into winged viviparae (see second picture above) that 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.

  • For Pemphigus gairi the axial length (= distance between two most distant points) of the primary rhinarium is less than 35 µm. The third antennal segment has 7-12 secondary rhinaria, the fourth has 3-6, the fifth has 1-4 and the sixth has 1-7.
  • For Pemphigus phenax the primary rhinarium on the fifth antennal segment is usually much enlarged, its axial length 35 µm or more with small islands. The third antennal segment has 6-12 secondary rhinaria, the fourth has 2-3, the fifth has 0-3 and the sixth has 2-5.

Pemphigus gairi host alternates between poplar and fool's parsley (Aethusa cynapium). In summer they live on the roots of the secondary host. Pemphigus gairi has been found in England, Czech Republic and Ukraine, but it probably occurs widely in Europe.

Pemphigus phenax host alternates between poplar and the roots of wild and cultivated carrots (Daucus carota). Apterae on carrot roots are pale lemon-yellow to yellowish white with white wax. Colonies may also persist parthenogenetically on carrots that remain in the ground through the winter. Pemphigus phenax is found in northern Europe (England, Denmark, France, Germany, Netherlands, Sweden), and is also recorded from Turkey and west Siberia.

Read more...

 

Pemphigus populi (Poplar cudweed pouch gall aphid)

In spring Pemphigus populi form green or greenish-yellow globular outgrowths of the mid-rib of the leaves of black poplar (Populus nigra) which are close to the base of the leaf (see first picture below) (cf. Pemphigus gairi & Pemphigus phenax which form yellowish or reddish elongate pouch-shaped galls which are more or less in the middle of a leaf). The outgrowths become club-shaped with the basal part narrower than the apex when mature.

The mature alatae (see first picture above) are greyish green with abundant wax. They have small but distinct marginal wax gland plates. The terminal process of the antenna (see second picture above) is 0.25-0.4 times as long as the basal part of the sixth antennal segment. They have 3-9 secondary rhinaria on the third antennal segment, 1-3 rhinaria on the fourth segment and 0-2 on the fifth segment. The sixth antennal segment is always without secondary rhinaria (cf. Pemphigus populinigrae, and Pemphigus gairi & Pemphigus phenax which all have some secondary rhinaria on the sixth antennal segment.) The apical segment of the rostrum is about 0.5-0.7 times as long as the second segment of the hind tarsus. Siphuncular pores are absent (cf. Pemphigus populinigrae, Pemphigus bursarius, Pemphigus gairi & Pemphigus phenax which all have siphuncular pores). The body is 1.5-2.4 mm long.

Pemphigus populi host alternates from various poplar species, mainly black poplar (Populus nigra) and lombardy poplar (Populus nigra 'italica'), to the roots of various species of Fabaceae, especially meadow vetchling (Lathyrus pratensis), black medic (Medicago lupulina) and tall melilot (Melilotus altissimus).

Read more...

 

Pemphigus populinigrae (Poplar cudweed pouch gall aphid)

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. The fundatrices (not pictured) are green or greyish green, and have no siphunculi. They have 4-segmented antennae which are about 0.17 times the length of the body.

The winged migrants (see second picture above) 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 the most basal rhinarium. 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.

Read more...

 

Pemphigus protospirae (Poplar polyspiral gall aphid)

In spring, Pemphigus protospirae forms green, or green mottled with red, smooth galls formed by slight thickening, flattening and spiral twisting of the leaf petiole of Populus nigra (black poplar). The galls of Pemphigus protospirae have more than three, and usually more than five twists (see picture below, cf. the gall of Pemphigus spyrothecae which is thicker and has 2-3 twists). The fundatrix that induces the gall has antennae about 0.2 × the length of the body and lacks siphunculi.

Image courtesy of Dimìtar Nàydenov under a Creative Commons Attribution-Share Alike 3.0 Unported license.

All the Pemphigus protospirae fundatrix offspring are winged. These offspring leave the gall during late spring to early summer (cf. the alate females that bear the Pemphigus spyrothecae sexual generation, which leave the gall from late August to November). Pemphigus protospirae winged migrants are greyish-green and lightly covered with waxy powder. Their antennae are 0.33 - 0.40 times their body length. The primary rhinarium on the fifth antennal segment is larger than that on the sixth, and is not fringed with hairs (cf. Pemphigus spyrothecae which has a small oval or rounded primary rhinarium on the fifth antennal segment, no larger than that on the sixth, and fringed with very fine short hairs). 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. Small siphuncular pores are present.

Winged migrants of Pemphigus protospirae emerge from their galls on poplar in late May to early July and move to aquatic umbellifers (Apiaceae) as secondary hosts. Pemphigus protospirae is less common than Pemphigus spyrothecae, probably because it is restricted by the localized distribution of its secondary hosts. Pemphigus protospirae is widely distributed in Europe, across to west Siberia and central Asia.The winged migrants move to aquatic umbellifers (Apiaceae) as secondary hosts.

 

Pemphigus spyrothecae (Poplar spiral gall aphid)

In spring, Pemphigus spyrothecae form green, reddish or yellowish, smooth galls formed by thickening, flattening and spiral twisting of the leaf petiole of Populus nigra (black poplar) with 2-3 twists (see picture below) (cf. the gall of Pemphigus protospirae which is thinner and usually has more than five spirals). The Pemphigus spyrothecae fundatrix is pale green, giving rise to a second generation of apterae within the gall.

The emigrant winged sexuparae emerge from the gall in late summer or autumn (cf. the emigrant alates of Pemphigus protospirae which emerge from the gall in late spring and early summer). They have a small oval or rounded primary rhinarium on the fifth antennal segment, no larger than that on the sixth, and fringed with very fine short hairs. (cf. Pemphigus protospirae where the primary rhinarium on the fifth antennal segment is larger than that on the sixth, and is not fringed with hairs). The emigrant alate of Pemphigus spyrothecaehas no secondary rhinaria on the fifth and sixth antennal segments (cf. Pemphigus protospirae which has 2-4 secondary rhinaria on the fifth, and 2-8 on the base of the sixth).

Pemphigus spyrothecae does not host alternate, but remains on Populus nigra (black poplar) all year. The fundatrix gives rise to a second generation of apterae within the gall, and the alate sexuparae emerge in August to November when they produce males and oviparae on the bark (cf. the emigrant alatae Pemphigus protospirae which leave the gall during late spring to early summer). The poplar spiral gall aphid is found throughout Europe as well as in North Africa, western Siberia and Pakistan, and has been introduced to Canada.

Read more...

 

Pemphigus trehernei (Sea aster root aphid)

Adult apterae of Pemphigus trehernei on the roots of sea aster, its secondary host, are yellowish white to greenish white (see first picture below). They are covered with greyish white wax which forms tufts on the abdomen, and also coats the roots upon which they feed (see second picture below). Characteristics which separate the 'bursarius' group of species (which includes Pemphigus trehernei) from other Pemphigus species, are: (a) the subgenital plate has a total of 13-16 hairs and (b) the last antennal segment (including the terminal process) is 0.89-1.24 times longer than the second hind tarsal segment. There are no morphological characters that can be used to differentiate apterae of Pemphigus species within the 'bursarius' group such as Pemphigus phenax, Pemphigus gairi, and Pemphigus bursarius. The body length of the adult Pemphigus trehernei aptera is 1.3-2.4 mm.

The emigrant alate of Pemphigus trehernei from poplar (obtained by experimental transfer) has antennal segment III 0.30-0.40 times the length of the hind tibia. Secondary rhinaria are distributed 11-19 on antennal segment III, 4-8 on segment IV, 4-10 on segment V and 6-11 on segment VI.

Pemphigus trehernei has only been found naturally on its secondary host, sea aster (Tripolium pannonicum). Aphid populations are largely confined to the edges of creeks and saltpans. Alate sexuparae are produced in September to December but overwintering of parthenogenetic generations on the roots of Aster tripolium is common. Alate sexuparae of Pemphigus trehernei have been transferred experimentally to lombardy poplar (Populus nigra var. italica), and subsequent generations produced globular green galls with a reddish tinge around the exit hole. Pemphigus trehernei has only been recorded from England, Ireland and France.

Read more...

Acknowledgements

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