InfluentialPoints.com
Biology, images, analysis, design...
Aphids Find them How to ID AphidBlog
"It has long been an axiom of mine that the little things are infinitely the most important" (Sherlock Holmes)

 

 

Identification & Distribution:

The adult apterae of Cavariella konoi are green or yellow-green, sometimes with rather faint darker green longitudinal stripe(s). The antennae, legs and siphunculi have brownish apices. The antennae are 0.31-0.50 times the length of the body, and the terminal process is 1.4-2.0 times the base of the last antennal segment (cf. Cavariella aegopodi   which has the terminal process less than 1.3 times longer than the base of the last antennal segment). The siphuncular wax is distinctly yellow (cf. Cavariella archangelicae   which has the siphuncular wax colourless to slightly greenish). Their siphunculi are 2.3-3.1 times the length of the cauda with the distal half swollen asymmetrically, being more curved on the inner side than on the outer side (cf. Cavariella archangelicae which has the distal half swollen in a nearly symmetrical way). The siphunculi are slightly shorter than (0.8-1.01 times) the head width across the eyes, and 5.0-7.3 times the maximum width of their swollen part. The supracaudal process has a broad basal part and is tongue-shaped about 0.5-0.8 times the length of the cauda. The body length of adult Cavariella konoi apterae is 1.6-2.9 mm.

The alate Cavariella konoi (see second picture below) has a dark abdominal patch on tergites III-V, but on tergite VI the dark cross band is broken into two dark spots (cf. Cavariella archangelicae which has tergite 6 with a dark cross band more or less continuous with the dark patch on the other segments.)

The clarified slide mounts below are of adult viviparous female Cavariella konoi : wingless fundatrix, and winged.

Micrographs of clarified mounts  by permission of Roger Blackman, copyright AWP  all rights reserved.

The spotted willow - angelica aphid host alternates from willow (Salix spp.) to angelica (Angelica). Sexual forms occur in October. The distribution of Cavariella konoi extends from Europe into Asia, North America and Mexico.

 

Biology & Ecology

Taxonomy

Heie (1980-1995)  described Cavariella konoi as having a 'darker green median stripe', whilst Blackman (2010) ) describes it as 'often having two rather faint darker green longitudinal stripes'. Most adult apterae in the colonies we have observed showed no sign of darker green markings on the dorsum, but were uniformly pale yellowish-green or pale yellow. The immatures, especially immature winged/brachypterous forms, often had darker green markings on the dorsum (see picture below).

The lack of green markings might suggest these were Cavariella archangelicae   rather than Cavariella konoi, but siphuncular shape, and measurements of siphuncular length and width at broadest point, together with head width, confirmed that most apterae were Cavariella konoi. There were alatae of both species present on the plant.

Several of the leaves of the food plant were extensively spotted with what appeared to be yellow wax (see picture below).

This is presumably the characteristic yellow wax that Cavariella konoi discharges from its siphunculi when alarmed (see picture above). This wax is a useful identification characteristic in the field. The very similar Cavariella archangelicae, which also favours angelica as its secondary host, discharges colourless to slightly greenish siphuncular wax.

 

Natural enemies

The very large colonies of Cavariella species that build up on secondary hosts attract many different natural enemies. Several Aphidius parasitoids have been observed parasitizing Cavariella konoi.

Various polyphagous predators also prey on Cavariella aphids. The hazel mirid Phylus coryli  is mainly found on hazel (Corylus avellana), but we have also found this mirid predating Cavariella konoi on angelica.

Pathogens also take a heavy toll, especially in the latter parts of the year.

 

Other aphids on same host:

Primary hosts

For lists of aphid species on willows (Salix) see our aphids on willow page. 

Secondary host

Blackman & Eastop list 15 species of aphid  as feeding on wild angelica (Angelica sylvestris) worldwide, and provide formal identification keys.

Of those aphid species, Baker (2015)  lists 11 as occurring in Britain: Aphis fabae,  Aphis gossypii,  Aphis spiraecola,  Cavariella aegopodii,  Cavariella konoi,  Cavariella konoi, Cavariella pastinacae,  Cavariella theobaldi,  Dysaphis angelicae,  Hyadaphis foeniculi  and Hyadaphis passerinii. 

Acknowledgements

Our particular thanks to Roger Blackman for images of his clarified slide mounts.

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