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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 instars have a role in defending the inhabitants of the galls.

 

Hamamelistes betulinus (Birch blister aphid)

Wingless females are greenish or dark brown to black and are normally covered in white wax as shown in the first picture below. The second picture shows specimens in alcohol without the wax. 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 apterae is about 1.5 mm. Winged females have 5-segmented antennae and pigmented siphuncular pores. The body length of alates is 1.3-2.0 mm.

 

In Europe and northern Asia, the birch blister aphid does not produce sexual forms and does not host alternate. It feeds on the undersides of birch leaves, mainly silver birch (Betula pendula), causing pale yellowish blisters to develop on the upper surfaces. It overwinters as first instar larvae on the twigs. In Japan, there is host alternation between the primary host forms develop on the leaves of Hamamelis 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 migrate to birch.

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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