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Uroleucon formosanumOriental lettuce aphidOn this page: Identification & Distribution Other aphids on the same hostIdentification & DistributionAdult apterae of Uroleucon formosanum (see first and third pictures below) are red, with a broad black or blackish red 'saddle' across the metathorax and abdominal tergites I-II. The eyes, antennae and siphunculi are also black, but the cauda is yellow, much paler than the siphunculi (cf. Uroleucon compositae, which has the cauda almost as dark as the siphunculi). The antennal tubercles are well developed, diverging and smooth; the median frontal tubercle is undeveloped. The antennae are longer than the body, and segment III bears 96-135 strongly protuberant circular secondary rhinaria scattered over the whole length (cf. Uroleucon sonchellum in North America, which has 49-93 secondary rhinaria on that segment, which do not protrude strongly). The terminal process is 4.8-6.3 times the base of antennal segment VI. The rostrum reaches beyond the middle legs. The legs are pale brown with the apical halves of the femora, apices of the tibiae, and the tarsi black. The siphunculi are cylindrical, but slightly expanded towards the base, about 1.5 times as long as the cauda, and reticulated on the distal third. The cauda is large, sword-shaped, and provided with about 8 pairs of long lateral bristles. The body length of adult Uroleucon formosanum apterae is 2.3-3.4 mm. Immatures are normally red, with short black siphunculi, but may occasionally be blackish red (see first picture below).
First image above copyright Onidira, second image copyright Licheng Shih, Alatae of Uroleucon formosanum (see second picture above) are dark red with the head and thorax blackish red, the antennae and siphunculi black and the abdomen dark red, except the basal part of the dorsum and the underside which are black. The cauda is yellow. The rostrum reaches the second pair of coxae. The wings are hyaline, the pterostigma pale yellow, and the veins yellowish brown. The legs are pale brown, with the apical halves of the femora, apices of the tibiae, and the tarsi black. The siphunculi are reticulated on the distal 0.4 of their length. In other respects the alate vivipara is similar to the apterous vivipara.
Image above copyright ahan88 under a Creative Commons License. Uroleucon formosanum feed on various Lactuca and Sonchus species. The feeding site is the stems, and along the midrib on the undersides of leaves. In more temperate climates, such as Korea and Japan, it is monoecious holocyclic, but in tropical areas populations are anholocyclic. Thus Takahashi (1921) notes that near Tokyo in Japan, the sexual forms make their appearance in November, but in Taiwan sexual forms do not occur. The species is one of the most common aphids in Japan, with winged forms also being common. The species is found in Japan, Korea, China, Taiwan, the Mariana Islands and east Siberia, and questionably in India. Other aphids on the same hostUroleucon formosanum has been recorded on 4 Sonchus species (Sonchus arvensis, Sonchus asper, Sonchus lactucoides, Sonchus oleraceus).
Uroleucon formosanum has been recorded on 7 Lactuca species (Lactuca dracoglossa, Lactuca indica, Lactuca raddeana, Lactuca sativa, Lactuca serriola, Lactuca sibirica, Lactuca triangulata).
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