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Aphis phaceliaePhacelia aphidOn this page: Identification & Distribution Other aphids on the same hostIdentification & DistributionThe fundatrix of Aphis phaceliae (see pictures below) has the posterior dorsum pale yellowish-green shading anteriorly to pale green or apple-green mottled with darker bluish-green, and a pale yellowish cauda. Apterous viviparae are rusty yellow on the head, with rest of the dorsum yellowish green or canary-yellow mottled with green anteriorly. The dorsum has no dark transverse intersegmental sclerites (cf. Myzus ornatus, which has conspicuous dark transverse intersegmental sclerites). The antennae are shorter than body length (cf. Illinoia phacelia which has antennae much longer than body length). They have weakly developed antennal tubercles, and secondary rhinaria are occasionally present on antennal segment III. The apical rostral segment (RIV+V) is 0.15 mm in length, 1.5-1.6 times the length of the second hind tarsal segment (HTII); it is longer than the cauda and bears 4-5 hairs. The prothorax and abdominal tergites I & VII have marginal tubercles. The siphunculi are dark (or sometimes pale with dark tips, given these pictures), and are cylindrical or somewhat tapering distally (cf. Myzus ascalonicus and Myzus persicae, which have slightly or moderately swollen siphunculi). The cauda is elongate, parallel-sided, with a light constriction or neck near the base, and bears 3 hairs on each side.
Images above copyright Andrew Jensen under a cc by-nc-sa licence. The Aphis phaceliae alate vivipara has 7-12 secondary rhinaria on antennal segment III, and 1-4 on segment IV. The head and thorax are black. The abdomen is pale apple-green with dorsal dark dashes, a darker green median line, and dusky patches near the siphunculi. The antennae, siphunculi, tarsi, and tips of tibiae are dark. The cauda is yellowish and the anal and genital plates are dusky. The fore wings have the media vein twice branched. The hind wings have two cross veins. Aphis phaceliae feeds on the leaves and stems of scorpionweed (Phacelia spp.). It is monoecious holocyclic, and is thought to have an abbreviated life cycle (see Jensen in aphidtrek). It is considered to be somewhat rare (Gillette & Palmer, 1929), although Jensen (ibid) noted that it could consistently be found on Phacelia in the spring growing on dry, disturbed soil such as south-facing road-cuts. The species has been found in the American northwest (Oregon, Washington, Idaho) south to Colorado. Other aphids on the same hostAphis phaceliae has been recorded on 2 scorpionweed species (Phacelia heterophylla, Phacelia nemoralis).
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