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Genus Clethrobius

Hairy birch aphids

On this page: Genus Clethrobius  Clethrobius comes 

Genus Clethrobius [Calaphidini]

Large hairy elongate brown aphids. All adult viviparae and males are winged; the ovipara is wingless. The antennae are shorter than the body. The abdominal dorsum has pigmentation confined to marginal sclerites plus a few bands. There are also bands of light wax pulverulence on the abdomen. The siphunculi are short and truncate, and the cauda is knobbed.

This genus comprises three or four Palaearctic species living on twigs and young branches of Alder (Alnus) and Birch (Betula) species. They have a sexual stage in their life cycle, but do not host alternate. They may be attended by ants

 

Clethrobius comes (Brown hairy birch aphid)

All adult viviparous female Clethrobius comes are winged. Freshly moulted viviparae (see first picture below) are light brown, but matured adult alatae (see second picture below) are dark brown or greenish black. The antennae, legs and cauda are black, apart from the bases of the femors which are pale. The antennae are much shorter than the body, with a terminal process that is 0.67-0.75 times the length of the base of the last antennal segment. The rostrum is very short, hardly or just reaching the middle coxae. Their siphunculi are dark sclerotic, shortly conical, in length about 0.6 times their basal width. The cauda is knobbed and distinctly constricted. The body length of winged Clethrobius comes viviparae is 4.1-4.4 mm.

 

The hairy birch aphid forms clusters on branches and twigs of Birch (Betula spp.), often where the new growth is dying back, or on twigs of Alder (Alnus spp.) overhanging streams. The populations on alder are regarded by some as a separate species, Clethrobius giganteus, and attempts to transfer aphids from birch to alder have not succeeded. However, no consistent morphological differences have been found. Sexual forms develop in October-November. Clethrobius comes occurs throughout Europe and across Asia to China, Korea and Japan.

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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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References

  •  Dixon, A.F.G. & Thieme, T. (2007). Aphids on deciduous trees. Naturalist's Handbooks 29. Richmond

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