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Identification & Distribution

Adult apterae of Aphis leontodontis (see first picture below) are greenish black with a brown head and no dark sclerotization on the dorsum (cf. Aphis picridicola, which has a marked dorsal abdominal sclerotic pattern). Assuming our pictures do indeed represent Aphis leontodontis (see note below), then there is a faint reddish-brown suffusion of the dorsum around the siphunculi, most noticeable in fourth instar immatures. The antennal terminal process is 2.1-2.6 times the length of base of antennal segment VI. Most hairs on antennal segment III are about 0.6 times the basal diameter of segment III, but a few hairs are frequently up to a little more than 1.0 times the basal diameter (cf. Aphis crepidis, Aphis hypochoeridis and Aphis taraxacicola, which have no long hairs on segment III). The abdomen has conspicuous, well-developed marginal tubercles on abdominal tergites II-IV (sometimes on V), as well as on tergites I and VII. The diameter of the marginal tubercle on tergite VII is 1.6-2.9 times the basal diameter of antennal segment III. The siphunculi are dark and are 1.4-1.8 times the length of the similarly dark cauda. The cauda is finger-shaped (cf. Aphis picridicola and Protaphis terricola, which both have a bluntly triangular cauda). The body length of adult apterae is 1.2-1.7 mm. Immature Aphis leontodontis are similarly coloured to the adult apterae with dark siphunculi.

Note: We cannot confirm our identification in this case as we obtained very few specimens (one adult aptera & a few immatures) for examination under the microscope - albeit the longest hairs on antennal segment III were 0.63 and 0.75 times the basal diameter of that segment. The only likely alternative identities of the aphid we found are Aphis crepidis or Aphis taraxacicola, but these have never previously been reported on Leontodon (albeit neither was Aphis hypochoeridis, see below).

The alatae of Aphis leontodontis (not pictured) have 5-10 secondary rhinaria on antennal segment III, 1-3 on segment IV, and 0-1 on segment V.

The images below show the single adult aptera collected, dorsal and ventral, in alcohol.

Aphis leontodontis is found on hawkweeds (Leontodon spp.) on the undersides of the etiolated basal parts of leaves at soil level and on the surface roots. There is no host alternation, and sexual forms develop in autumn. It is usually attended by ants, often with ant tenting. Aphis leontodontis has been recorded in parts of central and northern Europe (Denmark, Sweden, Germany, Poland, Byelorussia, Czech Republic) - but not previously in Britain.

 

Biology & Ecology

Discovery in Britain

Aphids feeding on the stem base or roots of plants have, not surprisingly, been under-recorded in the past. However, most such species are ant attended, and the presence of 'ant-tenting' over the basal leaves & rosettes is a very good indicator of aphid presence (or past presence) on the roots. A number of such aphid species are found on the stem bases & roots of the various yellow dandelion-like flowers (subfamily Cichorioideae in the Asteraceae) including the lesser hawkbit (Leontodon saxatilis, see picture of the flower below).

The bright yellow flowerheads with, on their undersides, the outer rays greyish-violet - plus the presence of forked hairs on the leaves (see picture below) distinguishes Leontodon taraxacoides from Crepis and Hypochaeris species, as well as from Leontodon autumnalis.

Two ant-attended aphid species are found on the stem base of various hawkweed (Leontodon) species in continental Europe: the striated hawkweed root aphid (Aphis picridicola) and the green hawkweed root aphid (Aphis leontodontis). Aphis picridicola is considered rare in Britain - Stroyan (1984) only recorded it from Glamorgan and Caernarvon. Aphis leontodontis has not previously been recorded in Britain.

From July to September during 2019, and in August 2020 we found Aphis picridicola to be frequent on the roots of lesser hawkbit (Leontodon taraxacoides = Leontodon saxatilis) at Birling Gap on the East Sussex coast. But in May 2020, when investigating ant-tenting on lesser hawkbit, we also found small numbers of what appears to be Aphis leontodontis (see picture below) on the undersides of the basal leaves and on the stem base. Their host plants were growing on a well-drained heavily-trampled chalk grass verge beside the South Downs Way.

 

Other aphids on the same host

Aphis leontodontis has been previously recorded on 3 species of Leontodon (Leontodon crispus, Leontodon hispidus, Leontodon incanus), 1 species of Scorzoneroides (Scorzoneroides autumnalis = Leontodon autumnalis) and, if we are correct in our identification, now also on Leontodon taraxacoides (=Leontodon saxatilis).

A new species for Leontodon roots

At Birling Gap in 2016 we found what we thought might be a yellow form of Aphis leontodontis, but the cauda is longer and more pointed and the siphunculus/cauda ratio is too low for Aphis leontodontis. We concluded these were Aphis hypochoeridis which has not previously been recorded on the basal stem/roots of Leontodon spp., but is common on the roots of cat's ear (Hypochaeris radicata).

In 2019 we again found Aphis hypochoeridis on Leontodon taraxacoides, this time on the coast at Barton-on-Sea in Hampshire, UK.

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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