The adult apterae of Cavariella archangelicae are green or yellowish. Their antennae are 0.35-0.39 times the length of the body and the terminal process is1.5-2.0 times the base of the last antennal segment. Their siphunculi are more than twice as long as the cauda with the distal half somewhat swollen in a nearly symmetrical way (cf. Cavariella konoi which has the distal half swollen asymetrically, being more curved on the inner side than on the outer side). The siphuncular wax is colourless to slightly greenish (cf. Cavariella konoi which has the siphuncular wax distinctly yellow ). The supracaudal process has a broad basal part and is tongue-shaped about 0.7-1.0 times the length of the cauda. The body length of Cavariella archangelicae apterae is 1.5-2.6 mm.
The alate Cavariella archangelicae has an uninterrupted dark cross band on tergite 6, thus continuing the dorsal black patch formed by the partially fused bands on tergites 3-5 (see second micrograph below, cf. Cavariella konoi which has the cross band on tergite 6 broken into two dark spots).
Micrographs of clarified mounts by permission of Roger Blackman, copyright AWP all rights reserved.
The willow - angelica aphid host alternates from willow (Salix spp.) to angelica (Angelica) and sometimes other umbellifers. Sexual forms occur in October. Cavariella archangelicae is found in Europe and western North America.
Our particular thanks to Roger Blackman for images of his clarified slide mounts.
Whilst we make every effort to ensure that identifications are correct, we cannot absolutely warranty their accuracy. We have mostly made 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).
I am contacting you at the suggestion of Alan Outen regarding an aggregation of aphids that I found on Angelica.
The attached photos were taken at Priory Country Park, Bedford (TL076496) on Sunday (24/08/14). The flower head was infested.
I looked up Angelica on your website influentialpoints.com and found a couple of candidate species. Cavariella archangelicae might be the best match, but I wasn't sure about the ID. (There is plenty of willow nearby).
Is it possible to identify the species from these photos please? I have specimens which I can pass on through Alan if a microscopic examination is desired.
Images copyright Keith Balmer, all rights reserved.
Unfortunately we cannot provide a definite identification from the photos you sent us because the only aphids we can see in sufficient detail are 4th-instar nymphs with developing wing buds. Your first image (above) does have 2 bright green adults in its center but, despite our best efforts, we cannot resolve the crucial features.