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Myzocallis meridionalisHamburger oak aphidOn this page: Identification & Distribution Other aphids on the same hostIdentification & DistributionUnusually for a Myzocallis species, adult viviparae of Myzocallis meridionalis may be apterous or alate. Adult apterae (not shown; but first picture below shows fourth instar, which has similar markings to the adult aptera) are yellow, with black antennae. Most noticeably there are dorsal pairs of black abdominal spots on segments IV-VI, which in fourth instar nymphs are fused medially appearing as three bars (cf. Myzocallis frisoni, which has 5 or 6 pairs of black abdominal spots in fourth instar alatoid nymphs). In adult apterae of Myzocallis meridionalis the spots are usually fused with each other forming a 6-lobed patch without intersegmental clear areas. The apterae normally bear secondary rhinaria on antennal segment III. Their femora are pale. The tibiae are dark at the base and become lighter at the tip, this difference is more pronounced on their hind tibiae. There are numerous intermediates between apterae and alatae in this species, with poorly developed wing pads or one or both wings lacking on one side. The body length of adult Myzocallis meridionalis apterae is 1.7-2.1 mm. Note: Myzocallis meridionalis belongs to a large subgenus, Lineomyzocallis, whose 17 species include Myzocallis granovskyi and Myzocallis walshii.
Both images above copyright Jon Hart under a creative commons licence. Alatae of Myzocallis meridionalis (see second picture above and pictures below) are bright yellow with a darker yellow head and thorax. Their antennae are black, except for segments I and II, and antennal segments IV and V are uniformly dark (cf. Myzocallis pepperi, which has segments IV & V lighter basally than apically). The antennae bear 3-4 secondary rhinaria on the basal half of antennal segment III (cf. Myzocallis frisoni, which has rhinaria distributed over more than the basal half). The terminal process of antennal segment VI is 2.3-3.5 times as long as its base. The antennal hairs are inconspicuous, being less than half as long as the basal diameter of antennal segment III. The prothorax has a black stripe on each side and the forewing has a black strip along the costal margin. Coxae, trochanters and most of the femora are yellow. The tips of the femora shade to dark, and the tibiae and tarsi are black, although the tips of the tibiae are slightly less pigmented. The cauda is knobbed and the anal plate is bilobate.
Both images above copyright Jon Hart under a creative commons licence. The first image above shows some younger immatures (instars I-III) of Myzocallis meridionalis alongside an alate. Note that the dorsal pairs of abdominal spots are still separate at this stage. The second image above shows an alate vivivipara giving birth. Myzocallis meridionalis lives on the undersides of leaves of oaks (Quercus) mainly water oak (Quercus nigra) and spotted oak (Quercus shumardii). Oviparae, with a black central dorsal patch like that of apterous viviparae, occur in December. However in the southernmost states parthenogenetic populations persist through winter on trees which keep their leaves. The hamburger oak aphid is found in south-eastern USA and Panama. Other aphids on the same hostMyzocallis meridionalis is recorded on 3 species of oak (Quercus lyrata, Quercus nigra, Quercus shumardii).
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