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Nasonovia williamsiLeafcurl cinquefoil aphidOn this page: Identification & Distribution Other aphids on the same hostIdentification & DistributionAdult apterae of Nasonovia williamsi (see picture below) are shining green to yellowish-green to amber yellow. Their antennae are mainly dusky, apart from segment VI which is dark. The antennae are 1.0-1.2 times the body length, with a terminal process that is 5.4-7.7 times the base of antennal segment VI. Secondary rhinaria are protruding and tuberculate, with 23-56 on antennal segment III, irregularly scattered along the whole the segment, 0-22 on segment IV, and 0-1 on V (cf. Acyrthosiphon vandenboschi on Potentilla in California, USA, which has no rhinaria on the antennal segment III). The longest hair on antennal segment III is 1.0-2.0 times the basal diameter of segment III. The apical rostral segment is slender, with almost parallel margins. It is 1.6-1.9 times the length of the second hind tarsal segment, and has 10-19 accessory hairs. There are rather large, pale, smooth, rounded or pear-shaped marginal tubercles present on the prothorax and abdominal segments II-V. The siphunculi are pale, sometimes with a dark apical part; they are almost cylindrical, thicker towards the base, almost smooth, sometimes with one or a few fine hairs, and 1.0-1.8 times the caudal length (cf. Chaetosiphon hottesi on Potentilla in North America, which has longer siphunculi, more than twice as long as the cauda). The cauda is pale, tongue-shaped, rather short and blunt, sometimes constricted, with 5(-6) hairs. The body length of adult Nasonovia williamsi apterae is 1.5-2.3 mm.
Image above copyright Andrew Jensen, under a creative common licence. The alate vivipara of Nasonovia williamsi may be pale, or it may have dusky or dark, indistinctly limited marginal sclerites and intersegmental pleural sclerites. Secondary rhinaria are tuberculate, with 46-70 on antennal segment III, 23-39 on IV and 3-11 on V. Siphunculi are dusky, pale, or pale with dusky apices. Nasonovia williamsi is monoecious on two species of cinquefoil (Potentilla) in western North America. These aphids occur on the under side of the leaves, causing them to curl up. Palmer (1952) reports finding apterous summer viviparae from May to August, and alate viviparae from July to August, but they were not common. Sexuales were unknown until Jensen (see Aphidtrek) found oviparae, alate males and eggs on curled basal leaves in Idaho in alate summer and early fall. Nasonovia williamsi is found in western USA (California, Idaho, Utah, Oregon, Nebraska) and Canada (Nebraska, Manitoba). Other aphids on the same hostNasonovia williamsi has been recorded on 2 Potentilla species (Potentilla arguta, Potentilla glandulosa).
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