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Protaphis are small to medium sized aphids that are adapted to feeding at the stem base and roots of plants where they are tended by ants. They have short appendages and other morphological features adapted to their mode of life.
There are about 50 Protaphis species, mostly in Europe and Central Asia, with a few in Africa and North America. They mostly feed at the stem bases or roots of the Asteraceae. They have a sexual stage in the life cycle, but do not host alternate. Protaphis are usually attended by ants.
Protaphis carlinae (thistle rosette aphid)
Adult apterae of Protaphis carlinae are dark blue-green, usually with reddish areas around the siphuncular bases. They have dark bars on the thoracic tergites and abdominal tergites VI to VIII, and dark patches on most of the other abdominal tergites. Both adults and immatures are wax-powdered. The antennal terminal process is 1.04-1.36 times as long as the base of antennal segment VI (cf. Protaphis terricola, which has the antennal process 0.80-0.95 times the base of that segment). Antennal segments III and IV are usually without rhinaria, and bear very short hairs, less than 0.3 times the basal diameter of antennal segment III (cf. Protaphis terricola, which usually has rhinaria on segments III & IV, and has somewhat longer hairs: 0.4-0.7 times the basal diameter of antennal segment III). Their siphunculi and cauda are very short. The cauda is pale or dusky, bluntly triangular, shorter than its basal width, and bears 10 or more hairs. The body length of adult apterae is 1.5-2.1 mm. Immature Protaphis carlinae are blue-green, with reddish areas around the siphuncular bases (cf. Protaphis terricola, which has light green immatures).
The alate Protaphis carlinae has fully sclerotized thoracic tergites, but is otherwise very similar to the aptera.
Protaphis carlinae has only been recorded feeding on the stem base and roots of carline thistles (Carlina spp.), especially the carline thistle (Carlina vulgaris) and the dwarf carline thistle (Carlina acaulis). Sexual forms develop in autumn, and the species overwinters as eggs. Protaphis carlinae are attended by ants. The species is present in south and eastern Europe, and is now known (from this report) to also be present in western Europe (southern England).
Protaphis middletonii (corn root aphid)
Adult apterae of Protaphis middletonii are pale green, bluish green, grey-green or olive-green, and more (see first picture below) or less (see second picture below) dusted with greyish wax. The apterae have 0-12 secondary rhinaria on antennal segment III. The antennal terminal process is 1.4-2.1 times as long as the base of antennal segment VI. The abdomen has dark marginal spots and also commonly some transverse black bands, but not an extensive solid black patch. Their legs are more or less dusky. The siphunculi are black, short, slightly thicker at base, and less than one tenth the body length. The cauda is also black and bluntly triangular. The body length of adult apterae is 1.5-2.5 mm.
Alatae have less apparent dark dorsal cross bands than the apterae. They have secondary rhinaria distributed 4-22 on segment III, 0-9 on segment IV, and 0-6 on segment V. Immature Protaphis middletonii are a somewhat paler green than the adults.
Protaphis middletoni occur on the roots of plants in numerous families including the Asteraceae, Brassicaceae, Poaceae, Lamiaceae and Apiaceae. Oestlund (1887) found it very plentiful on the roots of horseweed (Erigeron canadensis), and more rarely on giant ragweed (Ambrosia trifida). Jensen noted that Aphis middletonii is highly variable in habits and appearance, feeding both underground and low down on the stem above ground. Colonies are usually ant-attended. Sexual forms may develop in autumn, but anholocyclic overwintering is probably also common. Protaphis middletoni is found throughout western and central North America. Aphids of this group are also recorded from Asteraceae in Brazil, and from prickly pear (Opuntia) roots in Australia and South Africa.
Protaphis terricola sp. grp. (thistle rosette aphid)
Adult apterae of members of the Protaphis terricola species group are dark green with a powdery wax covering (see first picture below). In life they have a reddish suffusion around and between the siphunculi, that can be seen most clearly on the pale green immatures (see second picture below). Adult apterae have sclerotized patches on the dorsum on the thoracic segments, and on tergites VI and VII (see micrographs below). The length of the fused last two segments of the rostrum (RIV+V) is 1.2 to 1.4 times as long as the second segment of the hind tarsus (HTII) (cf. Protaphis anuraphoides where RIV+V is 1.45 - 1.65 times the length of HTII). The siphunculi have a weak flange and are 0.67 - 0.92 times the length of the cauda (cf. Protaphis anuraphoides which has siphunculi with a distinct flange and are 0.9 - 1.2 times the caudal length). The adult body length of Protaphis terricola sp. grp. is 1.3-2.0 mm.
Protaphis terricola sp. grp. concentrate on the shoot apical meristem of young plants in the ground rosette stage. Later in the year Protaphis terricola sp. grp. have been found feeding on the stem and inflorescences. There is no host alternation. The Protaphis terricola species group has previously been reported from southern, central and eastern Europe, the Middle East, and parts of Asia, and it has been introduced to South America.