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Myzocallis carpini

Hornbeam aphid

Identification & Distribution  Biology & Ecology 

Identification & Distribution:

Winged adult Myzocallis carpini viviparae (see first picture below) are pale yellow to yellowish white, with no dorsal abdominal markings. The forewing has a black spot at the base of the pterostigma. Their antennae are ringed with black, and antennal segment 6 is 4.4 to 5.3 times as long as the apical rostral segment. The apical rostral segment is at most 1.02 times as long as the second hind tarsal segment. The body length of alate Myzocallis carpini is 1.3-2.2 mm.

 

Immature Myzocallis carpini (see second picture above) and oviparae are similarly unmarked, and have the body hairs (and a few basal antennal hairs) capitate, and very much longer than those of viviparae. Males are winged, with secondary rhinaria along antennal segments III-VI (base) inclusive, and transverse dark bands on the abdominal dorsum.

The hornbeam aphid is found on the undersides of leaves of hornbeam (Carpinus betulus), especially when used for hedging. Myzocallis carpini is found in Europe, North Africa, the Middle East, and has been introduced into New Zealand and North America.

 

Biology & Ecology:

Stroyan (1977)  considered Myzocallis carpini widespread in Britain, but not very common. We have found it in Sussex more or less wherever the host is found, but it seldom reaches the same densities of some other Myzocallis  species such as Myzocallis coryli.

The nymphs are generally not aggregated in colonies, but are scattered over the leaves besides the veins, probably reflecting the original larviposition sites of the adult aphid. Note the prominent capitate hairs on the nymphs pictured above.

Large colonies of Myzocallis carpini on the ends of shoots on the undersides of the leaves of hornbeam have been reported by Budgeon (1979)  in New Zealand, where Myzocallis carpini is regarded as invasive. She also reported the occurrence of apparent intermediates - namely individuals with the wing bud and antennal characteristics of 4th instar nymphs , but containing well developed embryos with pigmented eyes. We suspect these are just normal fourth instar alatiform nymphs, which will moult to give adult alates.

Reports of natural enemies attacking Myzocallis carpini are few and far between. McEwen et al. (2007)  (quoting Szentkiralyi, pers. comm.) believed that larvae of the predatory chrysopids Hemerobius micans and Hemerobius humulinus preyed on this species. Populations of Myzocallis carpini were said to be high in spring (April to May) and autumn (September to November).

Barta (2009)  reported the first incidence of a fungal pathogen Entomophthora planchoniana attacking Myzocallis carpini, as well as other Myzocallis species such as Myzocallis castanicola  and Myzocallis walshii. The parasitoid Trioxys pallidus has been recorded from it by Tomanovic & Kavallieratos (2002) )

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

  •  Budgeon, L.A. (1979). First records of Myzocallis carpini (Koch) (Homoptera: Aphididae) in New Zealand. New Zealand Entomologist 7(1), 19-20. Full text 

  •  Barta, M. (2009). Entomophthoralean fungi associated with aphids in woody plants in the Arboretum Mlynany SAS. Folia Oecologica 36(1), 75-83. Full text 

  •  McEwen, P.K. et al. (2007). Lacewings in the Crop Environment. Cambridge University Press.

  •  Stroyan, H.L.G. (1977). Homoptera: Aphidoidea (Part) - Chaitophoridae and Callaphidae. Handbooks for the identification of British insects 2 (4a). Royal Entomological Society, London. Full text 

  •  Tomanovic, Z. & Kavallieratos, N.G. (2002). Trioxys Haliday (Hymenoptera:Braconidae:Aphidiinae) in Serbia and Montenegro. Acta entomologica serbica 7 (1/2), 67-81. Full text