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Genus Hamamelistes

Species Overview: Genus Hamamelistes  Hamamelistes betulinus 

Genus Hamamelistes [Macrosiphini]

Alates are distinguished by having two oblique veins in the hind wing.

There are five species in the genus host-alternating from galls (or "pseudogalls") on witch hazel (Hamamelis spp.) to galls on birch (Betula spp.), or remaining on one or other host all year. In some species the first instar nymphs have a role in defending the inhabitants of the galls.

 

Hamamelistes betulinus (Birch blister aphid)

Hamamelistes betulinus wingless females are greenish or dark brown to black (see first picture below after wax removal). They are normally covered in white wax and live in yellowish blister-like pseudogalls on birch (see second picture below). They have short, 3- or 4-segmented antennae. In European populations, they lack siphuncular pores, although siphunculi are present in some generations in Japan. The body length of Hamamelistes betulinus apterae is about 1.5 mm.

 

Winged females have 5-segmented antennae and pigmented siphuncular pores. The body length of Hamamelistes betulinus alates is 1.3-2.0 mm.

In Japan, there is host alternation. The primary host is Hamamelis japonica, where sexual forms develop and eggs are laid on twigs and trunks. These hatch the following year and the developing fundatrices induce coral-like galls to develop from flower buds. Winged forms then migrate to birch. In Europe and northern Asia, the sexual stage on the primary host is lost, the aphid stays all year on birch. It feeds on the undersides of birch leaves, mainly silver birch (Betula pendula), causing pale yellowish blisters to develop on the upper surfaces. Hamamelistes betulinus overwinters as first instar larvae on the twigs.

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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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