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Genus Thecabius

Poplar gall aphids

Species Overview: Genus Thecabius  Thecabius affinis  

Genus Thecabius [Panaphidini]

Small to medium-sized aphids (alate body length usually 2 - 3 mm) which have short antennae and siphuncular pores. Dorsal wax gland plates are present on all segments producing a dense covering of wax spicules.

About 17 species most of which host alternate and have a sexual stage in the life cycle. The primary host is poplar (Populus: Salicaceae) where it induces a gall on the leaves, petioles or branches. The secondary host is the roots or stems of plants such as buttercups (Ranunculus: Ranunculaceae), Lysimachia (Myrsinaceae) and sallow (Salix). They are not attended by ants.

 

Thecabius affinis (Poplar-buttercup gall aphid)

The fundatrix is green or bluish green. It is covered in wax and lacks siphunculi. The winged viviparous female is greenish, covered with wax spicules and has siphuncular pores. The antennae are short, about half the body length. The terminal process is 0.25 times the length of the base of the last antennal segment. The body length of winged females is 2.2-3.1 mm.

 

The fundatrix inhabits a small gall of its own on poplar (Populus) formed by folding the edge of a leaf. Its offspring leave this gall in May-June and move to other galls formed by feeding on the midrib of a young leaf which induces the leaf lamina to fold along the midrib towards the underside. The outer, upper side of the leaf becomes blistered and yellowish or reddish. Winged viviparous females leave the gall on poplar in late June-July to found waxy colonies at the stem bases and on the runners of buttercups (Ranunculus).

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

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