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Pentalonia [Macrosiphini]Pentalonia are rather small, oval to reddish-brown to blackish aphids. The head is spiculose with rather small conical scabrous antennal tubercles, and no median frontal tubercle. Antennae are 6-segmented, about as long as the body, with a very long terminal process. The apterae have no secondary rhinaria, but alates have a few scattered secondary rhinaria on antennal segments III-V. Antennal hairs are short; those on the body are short and broadly fan-shaped. First tarsal segments have 3-3-2 hairs (fore-mid-hind). The dorsal cuticle is wrinkled with some reticulation. Alatae have distinctive wings, with the forewing veins thickly brown-bordered; the radial sector is strongly curved, and fused with the media vein for part of its length, forming a closed cell. The hind wing is reduced, and has only one oblique vein. The siphunculi are rather thick, symmetrically clavate (=club shaped), black on the distal part, and with a large flange. The cauda is tongue-shaped with 4 hairs. Immatures have spinulose hind tibiae, as in Myzus. There are 4 species of Pentalonia known worldwide. Three species feed on either banana (Musaceae), ginger (Zingiberaceae) or Araceae, whilst the fourth has been found inside unfurling grass blades. One species in India is known to be holocyclic, with apterous oviparae and alate males, whilst the other two are mainly anholocyclic. Two species are restricted to South Asia, but the other two have a fairly cosmopolitan distribution in warmer countries, and in hothouses in temperate climates. Note: Baker (1920) comments that the abnormal venation of the forewing is unique, albeit it is only a little further development of the condition met with in Idiopterus. Pentalonia nigronervosa (Banana aphid) Cosmopolitan, glasshouses in temperate climatesAdult apterae of Pentalonia nigronervosa (see first picture below) are reddish-brown to blackish, with the antennal bases and apices, apical parts of femora and siphunculi dark and cauda dusky. The antennal tubercles are small and pointed. The antennae are about as long as the body with a long terminal process which is 6.2-7.5 times as long as of the base of segment VI. The rostrum reaches to behind the hind coxae, and the apical rostral segment (RIV+V) is 1.6-2.1 times as long as the second hind tarsal segment. RIV+V is nearly always more than 0.137 mm long (cf. Pentalonia caladii on Zingiberaceae and Araceae, which has RIV+V less than 0.137 mm). The siphunculi are 2.8-4.1 times the caudal length, with their distal 0.25 more-or-less swollen symmetrically. The siphunculi and femora are covered with irregular, transverse rows of spicules. The cauda is constricted near its base, divided into a basal, globoid part and an apical finger-shaped part, and bears 4 hairs. The body length of adult Pentalonia nigronervosa apterae is 1.2-1.8 mm. Immature Pentalonia nigronervosa are similar to adult apterae, but are generally a paler brown in colour.
Images above copyright Scot Nelson, public domain. Alatae of Pentalonia nigronervosa (see second picture above) have antennae about 1.2 times the body length, with a long terminal process, and 2-12 secondary rhinaria on segment III, 0-10 on segment IV and 0-6 on segment V. The wing veins are broadly shadowed with brown, with brown spots at their apices. The middle part of the radial sector of the forewing is fused with the media vein. Pentalonia nigronervosa feeds almost entirely on plants in the family Musaceae, with a few records from Heliconiaceae and Zingiberaceae. It is often found living under the old leaf bases, and is usually ant-attended (see third picture above). Alate males have been recorded, but in most places populations are thought to be entirely anholocyclic. It is an important vector of banana bunchy top virus which has severely affected banana production in some parts of the world (e.g. Samoa & Tonga). Pentalonia nigronervosa is widespread through all tropical and subtropical parts of the world, and in glasshouses in Europe, Australia and North America.
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