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)

 

 

Aphids on oak

Blackman & Eastop list about 225 species of aphids  as feeding on oaks worldwide, and provides formal identification keys for aphids on Quercus.

Here we focus on eight European species although some of these such as Tuberculatus annulatus now have a worldwide distribution. Assistance on differentiating the five species of oak that we consider is given below. 

 

Tuberculatus annulatus (Common oak aphid)

The winged viviparae are very variable in colour ranging from yellowish, greyish-green or pink to purple in summer. The antennae are pale apart from black bands at the tips of the segments. The terminal process of the sixth antennal segment of the antennae is 0.87-1.1 times the length of the base of that segment. Abdominal tergites 1-3 each have a pair of spinal processes, with those on tergite 3 particularly large (these processes are difficult to see on live specimens). The tarsi are black. The siphunculi are dark on the distal third or more. The body length of alates is 1.7-2.2 mm.

 

The common oak aphid is found on the undersides of leaves of oak (Quercus spp.), especially English oak (Quercus robur) and, less commonly, sessile oak (Quercus petraea). Winged males and wingless oviparae occur in October. It is distributed throughout Europe to Siberia and north-west China, and has been introduced to Australia, New Zealand, North and South America.

Read more... 

 

Myzocallis castanicola (Sweet chestnut aphid)

Winged adults are yellow. They are distinctively marked with a dark median strip on the head and thorax, and paired black spinal and marginal patches on the dorsal abdomen. The antennae are dark beyond the basal half of the third antennal segment. The tips of the tibiae and tarsi are dark, as are the forewing veins which end in fuscous spots. The siphunculi are also dark. The body length of alates is 1.6-2.3 mm. Immatures are yellowish with brown-black dorsal markings.

The sweet chestnut aphid is found on the undersides of leaves of many chestnut (Castanea) and oak (Quercus) species. It is found in Europe, Middle East, southern Africa, Australia, South America and western North America.

Read more... 

 

Myzocallis schreiberi (Holm oak aphid)

Winged adult viviparae are pale yellow, with the head and the thorax slightly darker. The prothorax often has short lateral streaks of dark pigment. The dorsal abdomen has small transversely oval, dark spinal spots and paler marginal sclerites. The legs are mainly pale and the siphunculi usually dark. The length of the last segment of the rostrum is usually greater than 1.2 times the length of the second segment of the hind tarsus (distinguishes from M. boerneri). The body length of apterae is 1.3-2.2 mm. Immatures are whitish to pale straw yellow with variable dorsal pigmentation.

The holm oak aphid lives on the undersides of leaves of holm oak (Quercus ilex) and only rarely on other oaks. Sexual morphs are unknown and viviparous forms can be found throughout the year. It is distributed through western and southern Europe.

Read more... 

 

Myzocallis boerneri (Turkey oak aphid)

Winged adults are yellowish, with the head and thorax sometimes partly dusky. The dorsal abdomen has small paired spinal and marginal specks of brown pigment. The antennae are pale but ringed with brown-black. The length of the last segment of the rostrum is usually less than 1.2 times the length of the second segment of the hind tarsus (distinguishes from M. schreiberi). The body length of apterae is 1.3-2.2 mm. The immatures are yellow-green with paired, dusky, indistinct spinal and marginal spots (not visible on young immatures below).

 

The Turkey oak aphid lives on the undersides of leaves of several oak (Quercus) species, especially the Turkey oak (Quercus cerris), but also holm oak (Quercus ilex) and sessile oak (Quercus petraea). It is widely distributed in Europe, the Middle East, and introduced to New Zealand, California and Argentina.

Read more... 

 

Thelaxes dryophila (Common oak thelaxid)

The wingless viviparae are oval, rather flattened,dark brownish-red to purplish grey with a paler spinal stripe. The antennae, legs, siphunculi and cauda are brownish. The antennae are 5-segmented and are slightly less than half as long as the body. The terminal process is less than half the length of the base of the last antennal segment. Hairs on abdominal tergite 5 are spine-like. This last character distinguishes the species from the very similar Thelaxes suberi which has those hairs very thick and dagger-like. Thelaxes suberi mainly occurs on oak species in southern Europe and in UK, but usually not on English oak (Quercus robur).

Winged females have a black head and thorax with the antennae, legs, cauda and areas around the siphunculi dark. The abdomen has dorsal cross bands on the rear segments and dark marginal plates. Unlike most aphids the wings are folded horizontally rather than tent like over the abdomen.

 

The common oak thelaxid does not host alternate and is found on many species of oak (Quercus spp.). Colonies at the tips of the shoots spread on to stems, leaf petioles and along mid ribs on the undersides of the leaves. They are also found on the developing acorns. It occurs in Europe, the Mediterranean region and south-west Asia.

Read more... 

 

Thelaxes suberi (Southern oak thelaxid)

Adult apterae of Thelaxes suberi vary in colour from pale green to dark brown (see pictures below). The terminal process of the sixth antennal segment is 0.26-0.40 times as long as the base of that segment. The hairs on abdominal tergite 5 are mostly more than 25um long, very thick and dagger-like. Thelaxes suberi siphunculi are very short and the knob of the cauda is at least as long as broad. The body length of adult aptera is 0.9-1.5 mm.

 

Thelaxes suberi live on the young shoots, leaves and developing acorns of Quercus spp. especially Quercus cerris and Quercus ilex (but not Quercus robur). Immature sexual forms apparently appear at the beginning of the summer, aestivate through the summer, and then adult oviparae and males occur in autumn. Thelaxes suberi is present in England, southern Europe, Mediterranean region, southwest Asia and South Africa.

Read more... 

 

Lachnus roboris (Variegated oak aphid)

Apterae are shining blackish brown. The dorsum has only a few short hairs. The antennae are quite short - for apterae 0.4-0.5 times the body length. There are two conical tubercles on the front of the mesosternum. The siphuncular cones are large and dark. The body length of apterae is 2.5-5.5 mm. Alates have the forewing membrane pigmented except for four clear patches (hence the name 'variegated').

 

Variegated oak aphids are found on twigs and small branches of oak (Quercus sp.) and sometimes sweet chestnut (Castanea sativa). They are present in Europe, the Mediterranean region and parts of the Middle East.

Read more... 

 

Tuberculatus borealis (Blue-green oak aphid)

Winged viviparae are pale blue-green, yellow mottled with green, or yellow, with blackish-banded antennae The terminal process of the sixth antennal segment of the antennae is 0.9-1.3 times the length of the base of that segment. Abdominal tergites 1- 4 each have a pair of spinal processes, but those on tergite 4 are sometimes very small (these processes are difficult to see on live specimens). The siphunculi are only apically dark (rarely over more than the distal half). The body length of alates is 1.9-2.3 mm.

The blue-green oak aphid is found on English oak (Quercus robur), more rarely on other oaks. It is found across northern Europe into western Russia and east to Iran. It has been introduced to North America.

Read more... 

 

Lachnus longirostris (Scarce variegated oak aphid)

Apterae of Lachnus longirostris are shining dark reddish to blackish brown. The siphuncular cones are rather small. The abdominal dorsum is densely haired with long, fine-pointed hairs. The middle parts of the tibiae are pale and the antennae are 0.4 - 0.5 times the body length. In addition the hind tibia has hairs on the ventral side which are often longer and finer distally, but not with some hairs 2-3 times longer than others. The alatae have a pattern of forewing pigmentation similar to Lachnus roboris, but with a more extensive clear area between Rs and media. Body length is 2.4 - 5.0 mm.

 

The first image shows the shining blackish-brown aptera. Note especially the hairy dorsum and the pale middle parts of the tibiae. These characteristics can be used to distinguish both apterae and alates of Lachnus longirostris from Lachnus roboris  on oak. In addition the wing patterning of alates is slightly different.

Scarce variegated oak aphids are found on twigs and branches of oak (Quercus spp.). A very similar species Lachnus pallipes occurs on beech. The differences between the two species are mostly size-related and they are considered by some authorities to be the same species feeding on different hosts. Lachnus longirostris is widely distributed in Europe.

Read more... 

 

Species of oak

The English oak (Quercus robur) (also called the common or pedunculate oak) grows to a height of 15-25 m.. Its leaves (see first picture below) have large deep lobes, smooth edges, a lobed base and a very short stalk. The acorns are born on long stalks (peduncles).

The sessile oak (Quercus petraea) (also called the durmast oak) grows to a height of 15-30 m. The leaves (see second picture below) have rather shallow, regular lobes. There are stellate hairs along the main veins on the underside of the leaf. The acorns are born on very short stalks .

 

The Turkey oak (Quercus cerris) grows to a height of 15-35 m. The leaves (see first picture below) are variable in shape but are generally longer and narrower than other species. Each rounded lobe ends in a point. There are tiny whiskers around the leaf bud, and on the acorn cup.

The American red oak (Quercus rubra) has large, broad leaves with deeply-cut toothed lobes (see second picture below). Each lobe ends in a small whisker.

 

Unlike other oaks, the holm oak (Quercus ilex) is evergreen. The leaves are shiny dark green with the underside covered in grey felt. Young leaves and leaves on young plants are spiny (see picture below), whereas older leaves and leaves on old plants have smooth edges.

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).

References

  •  Blackman, R.L. & Eastop, V.F. Aphids on the world's plants An online identification and information guide. Full text