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Oak and chestnut aphidsOn this page: Genus Myzocallis Myzocallis boerneri Myzocallis carpini Myzocallis castanicola Myzocallis coryli Myzocallis myricae Myzocallis schreiberi
Myzocallis are small, delicate, usually yellowish aphids. In most species the adult viviparae are all winged. The forewings are variably pigmented, but there is generally at least a dark spot at the base of the pterostigma. The siphunculi are stump shaped and are not flared at the apex. The cauda is knobbed and the anal plate is bilobed. Immatures usually have long, capitate dorsal hairs.
The Myzocallis genus comprises about 40 species living on oaks and chestnuts (Fagaceae). They have a sexual stage in the life cycle, but do not host alternate and are not attended by ants.
Myzocallis boerneri (Turkey oak aphid)
Immature Myzocallis boerneri (see first picture below) are pale yellow with paired, dusky, rather indistinct spinal and marginal spots. Winged adults of Myzocallis boerneri (see both pictures) are yellowish, with the head and thorax sometimes partly dusky. Their dorsal abdomen has small paired spinal and marginal specks of brown pigment. The antennae are pale but ringed with brown-black. The length of the last segment of the rostrum (RIV+V) is 0.84-1.25 times the length of the second segment of the hind tarsus (HTII) (cf. Myzocallis schreiberi in which the length of RIV+V is 1.2-1.5 times the length of HTII). The body length of Myzocallis boerneri apterae is 1.3-2.2 mm.
The Turkey oak aphid lives on the undersides of leaves of several oak (Quercus) species, especially the Turkey oak (Quercus cerris), but also holm oak (Quercus ilex) and sessile oak (Quercus petraea). Myzocallis boerneri is widely distributed in Europe, the Middle East, and has been introduced to New Zealand, California and Argentina.
Myzocallis carpini (Hornbeam aphid)
Immature Myzocallis carpini (see first picture below) are unmarked, and have the body hairs (and a few basal antennal hairs) capitate, and very much longer than those of the adult. Winged adult Myzocallis carpini viviparae (see second picture below) are pale yellow to yellowish white, with no dorsal abdominal markings. The forewing has a black spot at the base of the pterostigma. Their antennae are ringed with black, and antennal segment VI is 4.4 to 5.3 times as long as the apical rostral segment. The apical rostral segment is at most 1.02 times as long as the second hind tarsal segment. The body length of alate Myzocallis carpini is 1.3-2.2 mm.
The hornbeam aphid is found on the undersides of leaves of hornbeam (Carpinus betulus), especially when used for hedging. Myzocallis carpini is found in Europe, North Africa, the Middle East, and has been introduced into New Zealand and North America.
Myzocallis castanicola (Sweet chestnut aphid)
Immature Myzocallis castanicola (see first picture below) are yellowish or greenish with some brown-black dorsal markings. Winged adults of Myzocallis castanicola (see second picture below) are yellow with the wing venation distinctly outlined in brown and forewing veins ending in brown spots (cf. other oak-feeding Myzocallis whose wings are not distinctly outlined in brown). They are distinctively marked with a dark median strip on the head and thorax, and paired black spinal and marginal patches on the dorsal abdomen. Their antennae are dark beyond the basal half of the third antennal segment. The tips of the tibiae and tarsi are dark, as are the forewing veins which end in fuscous spots. The siphunculi are also dark. The body length of Myzocallis castanicola alates is 1.6-2.3 mm.
The sweet chestnut aphid is found on the undersides of leaves of many chestnut (Castanea) and oak (Quercus) species. Myzocallis castanicola is found in Europe, Middle East, southern Africa, Australia, South America and western North America.
Myzocallis coryli (Hazel aphid)
Immature morphs (see first picture below) have the body hairs, and sometimes a few basal antennal hairs, capitate and very much longer than those of adult viviparae. Winged adult viviparae of Myzocallis coryli (see second picture below) are pale yellow to yellowish white. Their antennae are ringed with black, with a terminal process that is 2.05-2.55 times the length of the basal part of antennal segment 6. The forewing has a black spot at the base of the pterostigma. The body length of Myzocallis coryli alates is 1.3-2.2 mm.
Myzocallis coryli oviparae are orange-yellow in colour, but when examined in alcohol they appear quite pale. Like the immatures, the oviparae have long capitate hairs.
The hazel aphid lives on the undersides of leaves of hazel (Corylus species). Like Myzocallis carpini, it may become abundant when its host is used for hedging. Myzocallis coryli is found in Europe, south-west Asia, north Africa, Japan, New Zealand, western North America, and South America.
Myzocallis myricae (Bog myrtle aphid)
Immature bog myrtle aphids are bright yellow with longitudinal rows of pale centred dark spots. Adult Myzocallis myricae alates are yellow or orange, with additional black longitudinal markings on the head and thorax. The antennae of bog myrtle aphids are shorter than their body, and the terminal process of their sixth antennal segment is less than twice the length of its basal part. The abdominal tergites 1 to 7 have paired dusky spinal and marginal sclerites. Myzocallis myricae siphunculi are short truncated cones. The tibiae have similar pigmentation to distal parts of the femora. Their body length is less than 3.5 mm.
Myzocallis myricae does not host alternate but feeds only on bog myrtle (Myrica gale). It is largely restricted to northern and western Europe. Sexual forms occur in autumn.
Myzocallis schreiberi (Holm oak aphid)
Immature Myzocallis schreiberi (see first picture below) are whitish to pale straw yellow with four longitudinal rows of dark spots and long body hairs. Winged adult viviparae of Myzocallis schreiberi (see second picture below) are pale yellow, with the head and the thorax slightly darker. The prothorax often has short lateral streaks of dark pigment. The dorsal abdomen has small transversely oval, dark spinal spots and paler marginal sclerites. The length of the last segment of the rostrum (RIV+V) is 1.2-1.5 times the length of the second segment of the hind tarsus (HTII) (cf. Myzocallis boerneri in which the length of RIV+V is 0.84-1.25 times the length of HTII). The legs are mainly pale and the siphunculi are usually dark. The body length of Myzocallis schreiberi apterae is 1.3-2.2 mm.
The holm oak aphid lives on the undersides of leaves of holm oak (Quercus ilex) and only rarely on other oaks. Sexual morphs are unknown, and viviparous forms can be found throughout the year. Myzocallis schreiberi is distributed through western and southern Europe.