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Giant reed aphidOn this page: Identification & Distribution Biology & Ecology Ant attendance Natural enemies Other aphids on the same host
Identification & Distribution
Adult apterae of Melanaphis donacis are pear shaped. The dorsum is dark purplish-brown, but this colour is largely obscured by thick white wax in a characteristic pattern (see first picture below). Their antennae are 6-segmented with segments I to the basal parts of IV pale, and the remainder brown. The antennal terminal process is 1.1-1.9 times as long as the base of antennal segment VI (cf. Melanaphis elizabethae in more northern climes, which has the terminal process 2.5-3.1 times the base of that segment). The longest hairs on antennal segment III are 0.6-1.1 times the basal diameter of that segment (cf. Melanaphis elizabethae, which has the hairs on that segment 1.1.-1.5 times its basal diameter). The apical rostral segment (RIV+V) is 0.5-0.7 times length of the second hind tarsal segment (HT II) (cf. Melanaphis sacchari, which has RIV+V more than 0.8 times the length of HTII). The dorsal body hairs are short and inconspicuous (cf. Sipha maydis, which has long spine-like dorsal hairs). The siphunculi are dark, stump-shaped and broadest at the base. The dusky cauda has 12-22 hairs. The body length of adult Melanaphis donacis apterae is 1.5-2.2 mm.
Images above copyright Katja Schulz under a Creative Commons Attribution License.
Alatae of Melanaphis donacis (one in colony pictured below) have much less wax than the apterae, with secondary rhinaria distributed 3-13 on antennal segment III, 0-3 on segment IV and none on segment V. Immatures and recently moulted individuals also have much less wax and are correspondingly more vulnerable to predators (see below).
Image above copyright Faluke under a Creative Commons Attribution License.
Melanaphis donacis is found on giant reed (Arundo donax) and common reed (Phragmites australis). Sexual forms have been found in southern France, with apterous males, but many populations worldwide are anholocyclic. The giant reed aphid is native to southern Europe, the Mediterranean region, north Africa, the Middle East, and Central Asia, eastward to India and Pakistan (Amin, 2019; Bodlah et al., 2017). It has been introduced to Argentina and Chile (Ortego et al. 2004,) and apparently also to California (see bugguide).
Biology & Ecology
Ant attendance of Melanaphis donacis appears to be facultative rather than obligatory, given that some authors do not mention their presence. However, in Pakistan Bodlah et al. (2017) observed ants of the genus Crematogaster attending colonies of Melanaphis donacis. Ant attendance has also been reported in Portugal (see picture below).
Images above copyright tiagorc under a Creative Commons Attribution License.
The picture below shows a colony of Melanaphis donacis being attended by Tapinoma ants in Morocco.
Image above copyright J. Philippe under a Creative Commons Attribution License.
Despite their protective wax, predators still take a toll on Melanaphis donacis especially on the very young nymphs which have little or no wax. The picture below shows a syrphid larva predating an immature in Spain.
Image above copyright Katja Schulz under a Creative Commons Attribution License.
Other aphids on the same host
Melanaphis donacis occurs on 2 species of Arundo (Arundo donax, Arundo plinii).
Blackman & Eastop list 14 species of aphid as feeding on giant reed (Arundo donax) worldwide, and provide formal identification keys (Show World list). Of those aphid species, Baker (2015) lists 10 as occurring in Britain (Show British list).
Melanaphis donacis occurs on 2 species of Phragmites (Phragmites australis, Phragmites karka).
Blackman & Eastop list 20 species of aphid as feeding on reed (Phragmites ) worldwide, and provide formal identification keys (Show World list). Of those aphid species, Baker (2015) lists 12 as occurring in Britain (Show British list).