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Identification & Distribution:

Adult apterae of Thelaxes suberi vary in colour from pale green to dark brown (see first picture 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 the abdominal tergites are long and conspicuous; those on tergite 5 are mostly more than 25µm long, and very thick and dagger-like (cf Thelaxes dryophila which only has short dorsal hairs and those on tergite 5 are spine-like). Thelaxes suberi siphunculi are very short and the knob of the cauda is at least as long as broad. The body length of Thelaxes suberi adult apterae is 0.9-1.5 mm.

The Thelaxes suberi alate (see second picture above) has a black head and thorax with the antennae, legs and areas around the siphunculi dusky. The abdomen has conspicuous dark marginal plates. The wings of Thelaxes suberi are folded horizontally, rather than tent-like, over the abdomen. Immatures are greenish-yellow sometimes with pinky-brown patches. The micrographs below show (first) a dorso-lateral view of a Thelaxes suberi aptera, and (second) a close-up of the dagger-like hairs between the siphunculi.

Thelaxes suberi live on the young shoots, leaves and developing acorns of many Quercus species, especially Turkey oak (Quercus cerris) and holm oak (Quercus ilex). Immature sexual forms 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.

 

Biology & Ecology:

We have only found this species in one location, on holm oak growing in a churchyard on the South Coast of England.

Mifsud et al. (2009) reported that Thelaxes suberi was frequent on Quercus ilex in the Maltese Islands, and often occurred concurrently with Hoplocallis picta and Myzocallis schreiberi. We have also found both these latter species on holm oak in southern England, although not with Thelaxes suberi.

Much like the related Thelaxes dryophila, Thelaxes suberi is often attended by ants.

 

The only predator we have found so far attacking Thelaxes suberi colonies is the two-spot ladybird (Adalia bipunctata).

 

Other aphids on same host:

Thelaxes suberi has been recorded from 20 Quercus species.

 

Damage and control

Species of Thelaxes have been reported to cause economic damage to ornamental oaks (Alford, 2012).

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

References

  • Alford, D.V. (2012). Pests of ornamental trees, shrubs and flowers: a colour handbook. Second Edition. Academic Press.

  • Mifsud, D. et al. (2009). Present status of aphid studies in Malta (Central Mediterranean) with special reference to tree dwelling species. Redia 92, 93-96. Full text