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Aphis picridicola (=Aphis striata =Protaphis funicularis)
Striated hawkbit root aphidOn this page: Identification & Distribution Biology & Ecology Life cycle Colour Ant attendance Other aphids on the same host
Identification & Distribution
Colonies of Aphis picridicola live basally on the rosette and root collar of hawkbit (Leontodon taraxacoides = Leontodon saxatilis), and related members of the Asteraceae, where they are tented with sand or soil particles by attending ants (see first picture below). Adult apterae of Aphis picridicola are bluish-grey, bluish green or pale green with a greyish wax bloom (see second picture below). The antennae normally have 6 segments, although in some smaller individuals segments III and IV are more-or-less fused. The antennal terminal process is 1.5-1.9 times the length of the base of antennal segment VI. The rostrum is rather long with the fused apical rostral segment 1.21-1.36 times the length of the second hind tarsal segment. There is a marked dorsal abdominal sclerotic pattern characterised by a tendency for the dark intersegmental sclerites to enlarge, especially on tergites IV-V where they form large spreading dark patches just in front of the siphuncular bases. Spinal bands and marginal sclerites are also present on most segments. Marginal tubercles on abdominal segments I and VII are rather large. The siphunculi are rather short, only 0.9-1.11 times the length of the short subtriangular cauda. The body length of adult Aphis picridicola apterae is 1.4-2.1 mm.
The alate Aphis picridicola (not pictured) has large marginal sclerites on tergites II-IV but not on V, no postsiphuncular sclerites, short bands on tergites VII-VIII, and two distinct series of dark pleural intersegmental muscle sclerites, the outer series lying very near the marginal sclerites. There may also be small spinal sclerites on tergites I-VI. Immatures (see third picture above) are greenish with or without faint dark intersegmental markings.
The micrographs below show an adult aptera of Aphis picridicola dorsal and ventral, in isopropanol.
Aphis picridicola was formerly assigned to subgenus Protaphis, but has since been moved to genus Aphis, subgenus Pseudoprotaphis - and Protaphis is considered to have full genus status.
The striated hawkbit root aphid does not host alternate, but lives year-round on hawkbits (Leontodon species), catsears (Hypochaeris spp.) and hawkweed oxtongue (Picris hieracioides). Apterous males and oviparae are produced in autumn, and the species overwinters as eggs on the basal leaves. Aphis picridicola is rare in Britain, but is found throughout Europe into west Siberia.
Biology & Ecology
We found Aphis picridicola for the first time in August 2019 on flowering Leontodon taraxacoides plants growing in short downland turf beside a track at Birling Gap, East Sussex.
Host plant identification was confirmed by the yellow florets having toothed tips (see first picture above) with outer florets greyish-violet beneath, the leaves broadest above the middle, untoothed to pinnately lobed (see second picture above), and the presence of forked hairs on the leaves & stem (see third picture above).
So far we have only found adult and immature apterous viviparae. The adult apterae are very distinctive with a marked dorsal abdominal pattern (see pictures of adult aptera above and below).
Colonies of these aphids were still active on Leontodon in mid-September, but so far we have found no sexual forms.
Both immatures and adults have a wax 'bloom', which is more noticeable on the immatures (see pictures below) than on the adults.
In general immatures are a lighter green than the blue-green adult apterae. We think the apterae in the first picture below are fourth instars, although they could be lightly marked adults.
The second picture above appears to show an unmarked fourth instar aptera, or possible a teneral (=recently moulted) adult that has yet to develop its dorsal sclerotic pattern.
Colonies of Aphis picridicola at Birling Gap were invariably tented over by ants with soil and sand particles. The species of ant is as yet unidentified, but it would appear to be a thermophilic species given its habitat at the coast. Its attendance of the aphids was very sensitive to disturbance.
Mifsud et al. (2011) reported finding Aphis picridicola in June on the lower leaves and root collar of Hypochaeris achyrophorus in the Maltese Archipelago. They were attended by the ants Tetramorium semilaeve and Plagiolepis pygmaea.
Other species on the same host
Aphis picridicola has been recorded from three species of Leontodon: lesser hawkbit (Leontodon saxatilis = Leontodon taraxacoides), bristly hawkbit (Leontodon hispidus) and Leontodon crispus. It has also been recorded from one species of Picris: hawkweed oxtongue (Picris hieracioides); and from four species of Hypochaeris: Mediterranean cat's ear (Hypochaeris achyrophorus), smooth cat's ear (Hypochaeris glabra), spotted cat's ear (Hypochaeris maculata) and catsear (Hypochaeris radicata).