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Wild lettuce aphidOn this page: Identification & Distribution Other aphids on the same host
Identification & Distribution
Adult apterae of Uroleucon pseudambrosiae (see first picture below) are red to red-brown or dark brown, with black antennae and siphunculi, and a pale or dusky cauda much paler than the siphunculi (cf. the Asian species Uroleucon compositae & Uroleucon lactucicola which have the cauda almost as dark as the siphunculi). The legs have the coxae and the basal two thirds of the femora pale, the distal part of the femora black, and the tibiae yellowish-brown with dark apices. The antennae have 16-39 secondary rhinaria on segment III (cf. Uroleucon sonchellum, which has 49-93 secondary rhinaria on segment III). The hairs on that segment are 0.025-0.035 mm in length. The rostrum reaches the third pair of coxae. The second hind tarsal segment (HTII) is long and thin, being about the same length (0.9-1.1 times) as the apical rostral segment (RIV+V) (cf. Uroleucon ambrosiae, which has HTII shorter, only 0.75-0.85 times the length of RIV+V). There are no antesiphuncular sclerites present (cf. Uroleucon picridis, which has antesiphuncular sclerites). The siphunculi are rather thick, their apical third is reticulated, and they are 1.1-1.5 times the caudal length (cf. Uroleucon bicolor and Uroleucon murale, which have long, thin siphunculi, 1.5-2.0 times the length of the cauda). The cauda has 20-32 hairs. The body length of adult Uroleucon pseudambrosiae apterae is 2.2-3.4 mm.
Images above copyright David Cappaert, Bugwood
Alate Uroleucon pseudambrosiae (see second picture above) are similarly coloured to the apterous forms, except that late in the season alate forms on dying Lactuca often have a greenish cast. The alate vivipara has 36-53 secondary rhinaria on antennal segment III. The longest hairs on antennal segment III are 0.025-0.03 mm. The rostrum surpasses the second pair of coxae. Marginal tubercles are absent. The siphunculi have the apical third reticulated, and the cauda has 13-27 hairs.
The most common host for Uroleucon pseudambrosiae is wild lettuce (Lactuca spp.), although it has also been recorded from many other genera in the Asteraceae. The species is monoecious holocyclic and produces oviparae and alate males in autumn. The wild lettuce aphid is found in Canada, and eastern USA south to Florida, and has been introduced to Europe (Poland).
Other aphids on the same host
Uroleucon pseudambrosiae has been recorded from 7 lettuce species (Lactuca biennis, Lactuca canadensis, Lactuca hirsuta, Lactuca jamaicensis, Lactuca sativa, Lactuca serriola, Lactuca virosa).
Uroleucon pseudambrosiae has been recorded from 2 ragweed species (Senecio anomymus, Senecio aureus).