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Eastern dusky-winged oak aphidOn this page: Identification & Distribution Other aphids on the same host
Identification & Distribution
Adult alatae of Myzocallis discolor (see first two pictures below) are largely yellow-green with highly variable amounts of black and red on the head, prothorax and abdomen (the red is lost and the black shows brown in prepared specimens - see fourth picture below). The forewings vary from being almost clear to heavily pigmented. The antennal tubercles are poorly developed. The antennae have darker rings at the apices of the segments. The antennal terminal process is 2.0-2.5 times length of base of segment VI. Segment III bears 4-12 secondary rhinaria distributed over most of its length (cf. Myzocallis pseudodiscolor, which has 3-6 secondary rhinaria distributed over most of the length of segment III). The hairs on the antennae are pointed, and are shorter than half the basal diameter of antennal segment II. On the abdomen there are four rows of irregular dark spots, often with smaller dots between them; the two middle rows becoming confluent just above the siphunculi. Dorsal abdominal hairs, whilst sometimes pointed, are normally minutely capitate. Myzocallis discolor has dark pigmented siphunculi (cf. Myzocallis punctata, which has pale colourless siphunculi), and the siphunculi are without an apical flange. The cauda is knobbed and the anal plate is deeply bilobate.
Note: The species Myzocallis asclepiadis, Myzocallis discolor, Myzocallis punctata and Myzocallis tuberculata are all in same subgenus, Neomyzocallis, the latter three feeding on oak. The species Myzocallis alhambra Davidson & Myzocallis mimicus Richards have both been synonomized to Myzocallis punctata.
First picture above copyright Jesse Rorabaugh under a public domain licence (CC0)
Immature Myzocallis discolor (see newborn in second picture above, and IV-instar first below) are pale yellowish green, often with reddish blotches, and bear long capitate hairs. The second picture below shows a clarified mount of a Myzocallis discolor - note especially the dark siphunculi, which is the easiest character with which to discriminate this species from Myzocallis punctata.
First picture above, copyright James Bailey under a creative commons licence;
Myzocallis discolor feeds on several oak species including white oak (Quercus alba), live oak (Quercus virginiana) and chestnut oak (Quercus prinus) - and perhaps rarely on bur oak (Quercus macrocarpa), which hosts Myzocallis pseudodiscolor. Palmer (1952) found Myzocallis discolor apparently rare in Colorado Springs, Colorado, USA, although Davis (1910) found it common in Illinois. The eastern dusky-winged oak aphid is widely distributed in North America (the 'eastern' in the English name of this aphid is a misnomer) and is also found in Cuba and Costa Rica.
Other aphids on the same host
Myzocallis discolor has been recorded from 13 oak species (Quercus alba, Quercus bicolor, Quercus coccinea, Quercus gambelii, Quercus macrocarpa, Quercus michauxii, Quercus muehlenbergii, Quercus oleoides, Quercus palustris, Quercus prinus, Quercus sapotifolia, Quercus texana, Quercus virginiana).