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Thelaxes dryophila

Common oak thelaxid

Identification & Distribution 

Identification & Distribution:

The wingless viviparae of Thelaxes dryophila are oval, rather flattened, dark brownish-red to purplish grey with a paler spinal stripe. Their antennae, legs, siphunculi amd cauda are brownish. The antennae are 5-segmented and are slightly less than half as long as the body. Their 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 Thelaxes dryophila 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 of Thelaxes dryophila 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. Thelaxes dryophila occurs in Europe, the Mediterranean region and south-west Asia.

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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