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Myzocallis schreiberi

Holm oak aphid

On this page: Identification & Distribution  Biology & Ecology 

Identification & Distribution:

Winged adult viviparae of Myzocallis schreiberi (see first picture above) 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 are 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 Myzocallis boerneri ). The body length of Myzocallis schreiberi apterae is 1.3-2.2 mm.

Immature Myzocallis schreiberi (see second picture above) are whitish to pale straw yellow with variable dorsal pigmentation and markedly longer body hairs than the adult. The micrographs below show an adult alate and an immature Myzocallis schreiberi.

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. Myzocallis schreiberi is distributed through western and southern Europe.

 

Biology & Ecology:

Quercus ilex presents a difficult habitat for aphids as the young shoots and lower surface of the leaves are covered with very smooth trichomes.

 

Kennedy (1986)  looked at whether mode of attachment to the host may be the basis for specialization in aphids. He found that although Myzocallis schreiberi could walk freely on both its regular host Quercus ilex and on Quercus robur, the related aphid species Tuberculatus annulatus  could only move freely on Quercus robur. Myzocallis schreiberi achieved attachment to the rough textured leaves of Q. robur by means of pretarsal claws, and to the smooth upper surface of trichomes on the lower surface of Q. ilex using flexible pretarsal empodia. The latter were not possessed by Tuberculatus annulatus.

We have observed a number of predators active against Myzocallis schreiberi. Syrphid larvae such as the one below are not uncommon.

Coccinellids are also sometimes abundant on the tree feeding on the Myzocallis and Hoplocallis aphids. Very few parasitoids have been recorded attacking Myzocallis schreiberi, and we have only found one parasitized mummy of this species (see below).

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).

Useful weblinks 

References

  •  Kennedy, C.E.J. (1986). Attachment may be the basis for specialization in aphids. Ecological Entomology 11(3), 291-300. Abstract