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Genus Colopha

Cockscomb gall aphids, elm-sedge aphids

On this page: Genus Colopha  Colopha compressa 

Colopha [Eriosomatini]

Colopha is a small aphid genus, related to the genus Kaltenbachiella.  Apterae on the secondary host differ from Kaltenbachiella apterae in having the fore-tarsi parallel-sided, with a ventral hair arising from a distal protrusion. Alatae have a once-branched media in the fore wing and one oblique vein in the hind wing.

There are 6 Colopha species worldwide, all in the northern hemisphere. Three of these have a sexual stage, and host alternate from elm, where they live in cockscomb-like galls, to grasses or sedges, where they live on the roots or aerial parts. Three species have lost their primary host and their sexual stages and live parthenogenetically year-round on grasses and sedges.

 

Colopha compressa (Elm cockscomb gall aphid)

The fundatrices of Colopha compressa induce laterally compressed cockscomb-shaped galls along the midrib on the upper surface of elm leaves (see first picture below). These galls are yellowish, often tinged with red. Fundatrices (not shown) are yellow or yellowish green and are lightly covered with waxy powder. Their antennae are about 0.12 times as long as the body. The body is oval or elongate, with wax plates on each of the thoracic and abdominal segments, and small siphuncular pores - which may be present or absent. The yellowish offspring of the fundatrices (see second picture below) develop to green alatae which leave the gall. These produce dark yellow apterae on the secondary host which have a body length of 0.9-1.5 mm, and secrete flocculent wax.

Both images copyright Maria Fremlin,  all rights reserved.

Alatae emerge from their galls on elm (Ulmus) in July, from an opening on the underside of the leaf, and colonise the roots of sedges (Carex) and cottongrass (Eriophorum). Alate sexuparae return to elm in September-October, although some populations may persist on the roots of sedges throughout the winter months. Colopha compressa is found throughout Europe, east to Turkey, Ukraine and Kazakhstan, and has been introduced to Siberia.

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Acknowledgements

We especially thank Maria Fremlin for the images of Colopha compressa shown above.

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 sp 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

  • Blackman, R.L. & Eastop, V.F. (2006). Aphids on the world's herbaceous plants and shrubs. Vols 1 and 2. John Wiley & Sons.