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Genus Tuberculatus [Panaphidini]

Adult Tuberculatus viviparae are always winged and are characterized by having one or more tubercular abdominal spinal processes. Their antennae are as long as the body or longer. Their siphunculi are short, truncate and smooth - and the cauda is knobbed.

There are about 60 species of oak- and chestnut-feeding aphids in the Tuberculatus genus. The genus includes some well-defined subgenera of limited distribution; those detailed below represent Tuberculoides found in the western palaearctic.

 

Tuberculatus annulatus (Common oak aphid)

Immature Tuberculatus annulatus are yellowish or green (see first picture below) with pale antennae apart from black bands at the tips of the segments. The adult winged viviparae (see second picture below) are very variable in colour ranging from yellowish, greyish-green or pink to purple in summer. 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 (=protrusions). (cf. Tuberculatus borealis  which has a pair of spinal processes on each of tergites 1-4).
Warning:
Since they are under the folded wings, these processes can be difficult to see on live specimens!

The spinal processes on tergite 3 are particularly large (cf. Tuberculatus neglectus  which has spinal projections on abdominal segment 1-3 of similar size), and may be dusky pigmented. The tarsi are black. The siphunculi of adult alates are dark on the distal one third to two thirds.. The body length of Tuberculatus annulatus 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. Tuberculatus annulatus is distributed throughout Europe to Siberia and north-west China, and has been introduced to Australia, New Zealand, North and South America.

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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.

 

Tuberculatus neglectus (Sessile oak aphid)

Adult apterae of Tuberculatus neglectus are yellowish with a darker yellow mesothorax. The eyes are whitish yellow, and the pale antennae are banded with black. The antennal terminal process is 1.14-1.53 times longer than the base of the sixth antennal segment (cf. Tuberculatus annulatus  in which the antennal terminal process is 0.87-1.14 times as long as the base of the sixth antennal segment). The three pairs of spinal tubercles on abdominal segments 1-3 are of similar size (see first picture below) (cf. Tuberculatus annulatus which has the most anterior tubercle much larger than the other two) . The siphunculi (see second picture below) are dark except at the base, and are longer than the knob on the cauda. The body length of the adult alate Tuberculatus neglectus is 1.4-2.2 mm.

Tuberculatus neglectus lives on the undersides of leaves of sessile oak (Quercus petraea). It occurs more rarely on English oak (Quercus robur) and on hybrids between the two oak species. Sexual forms can be found in November. It is found in northern and north-west Europe.

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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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