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Sycamore periphyllus aphidOn this page: Identification & Distribution Biology & Ecology Life cycle Defensive behaviour Ant attendance Natural enemies Damage & Control Other aphids on the same host
Identification & Distribution:
Adult Periphyllus acericola apterae are pale green or yellowish green, with darker green flecks and sometimes with dorsal brownish markings (see first picture below). The tips of the antennal segments are dark and the terminal process is 2.3 - 3.0 times longer than the base of the last antennal segment. The longer of the two hairs on the base of antennal segment VI is more than half as long as the base of antennal segment VI (cf. Periphyllus testudinaceus and Periphyllus californiensis which have the longer of the two hairs on the base of antennal segment VI less than half as long as the base of antennal segment VI) . The head and pronotum are pale as are the legs and the siphunculi. The siphunculi are stump shaped, their lengths a little less than their basal diameters. The width of the base of the cauda is more than twice the length of the cauda. The adult Periphyllus acericola aptera body length is 2.4-3.5 mm. Note: it is easier to confirm identification of the alates (see below) than the apterae.
Periphyllus acericola alates (see second picture above) have broad dark dorsal abdominal cross-bars scarcely separated between segments. The pterostigmata of the wings are very black and darker than the marginal sclerites (cf. Periphyllus testudinaceus which has the pterostigma of the wing paler than the marginal sclerites). The adult alate body length is 3.0-3.5 mm. The Periphyllus acericola fundatrix is greenish-brown and strongly hairy with numerous black tubercles. It is unusually large, with a body length of up to 4.5 mm.
The sycamore periphyllus aphid is found on the undersides of leaves, petioles and young shoots of sycamore (Acer pseudoplatanus). It is sometimes attended by ants. Periphyllus acericola is found through most of Europe.
Biology & Ecology
The overwintering eggs hatch in spring. Periphyllus acericola nymphs feed on the one year shoots of sycamore, maturing to large fundatrices by mid-April (see picture below).
Note the fundatrices are markedly larger than any of the other morphs. Their offspring, when young nymphs (see first picture below), move to the buds of sycamore where they feed on the very young leaves.
Those that survive the predators and parasitoids mature to apterae and alates. This picture shows a group of developing nymphs with wing buds and a few that have matured to adult alates. The very pale alate has only just moulted to become a winged adult. Then in late May the Periphyllus acericola adults start producing rather different first instar nymphs known as dimorphs which are yellowish white with long, pointed hairs (see pictures below). These do not develop immediately, but aestivate through the summer. They aggregate in dense groups appearing like whitish spots on undersides of leaves.
In late summer the aestivating nymphs of Periphyllus acericola resume development as shown in the picture below. Note the adult apterae have some dorsal brownish markings.
Premature yellowing of the leaf often occurs where large colonies havbe been feeding (see picture below).
Shearer (1976) has demonstrated that aphids reared on such areas are heavier than ones reared on other parts of leaf. This suggests that the aphid aggregations act as sinks diverting nutrients towards aphid colonies.
The sexuales develop in October. Several oviparae are shown in the first picture above. Alate males (see second picture above) also occur at this time and these mate with the oviparae. The oviparae then lay the overwintering eggs on the twigs and branches of the sycamore.
We describe the aestivating nymphs of Periphyllus acericola above. It might be thought that aggregating in dense pale-coloured groups would make the nymphs especially vulnerable to predators like the chiffchaff, a well known aphid predator which searches the undersides of leaves for insects.
However, sycamore leaves often have numerous cream or white erinea induced by the gall mite Aceria pseudoplatani. The erinea are hairy and likely to be very unpalatable to predators. They are similar in appearance at any distance to the diapausing aphid colonies. It seems probable these aphids have evolved to mimic the appearance of the erinea (see cryptic coloration in aphids) and thus not attract the interest of predators.
The remaining apterous adults also appear to enter a state of diapause (or maybe just immobility), but they use a different form of the 'crypsis' strategy to avoid predation. They adopt 'colour matching' to the normal leaf colour pattern i.e. pale green with a network of darker green veins (see picture below showing four apterae with alate and diapausing nymphs).
Some (but not all) colonies of Periphyllus acericola are attended by ants, in this case by Formica rufa (Southern Wood Ant). One of the ants in the first image is making a threat display to defend the aphid (against us) by opening his mandibles (jaws). The second image suggests that they are sometimes unsuccessful in defending the aphids against parasitoids given that there is an aphid mummy on the stem. Particular species of attending ants may only protect against certain types of predators and parasitoids, and some parasitoids have evolved behaviour patterns which resemble those of ants and may thus protect them.
The picture above shows a female braconid inserting an egg in the aphid's body.
Large clusters of aphids may be parasitized as shown in the first picture above. Predators also take their toll - the second picture above shows a coccinellid, an adult 14-spot Ladybird (Propylea quattuordecimpunctata), consuming a sycamore periphyllus aphid.
The picture above shows a syrphid larva predating Periphyllus acericola aphids.
Other aphids on same host:
Periphyllus acericola has been recorded from 3 Acer species (Acer campestre, Acer granatense, Acer pseudoplatanus).
Damage and control
There appear to have been no studies on the effect of Periphyllus acericola on their host plant. Since aphids can be very numerous, the amount of sap removed will be considerable, which would reduce the growth rate of the host plant. If the population is ant-attended, the adverse effects would be counteracted to an unknown degree by predation of leaf feeders by the ants.