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Microparsus [Macrosiphini]Microparsus are mostly brightly-coloured aphids, with several characteristics indicating a close relationship of this genus with Macrosiphum. The antennal tubercles are distinct. The antennae are six-segmented, with subcircular secondary rhinaria on antennal segment III. They are differentiated from Macrosiphum and any other named genus by the wing characters. The radial sector is short and strongly curved. The media vein is typically two branched. The cubital veins are heavily shadowed. The hind wing is minute, the tip extending only to about the Cu1b of the fore wing, and is correspondingly narrow. The costal hooks of the hind wing are very near the tip of the wing. Typically the hind wing has only the radius, without oblique veins. Apterae have marginal tubercles on abdominal tergites II-IV. The siphunculi are cylindrical in subgenus Microparsus, but clavate (=swollen) in subgenus Picturaphis. The anal plate is hemispherical, and the cauda is long and tapering. There are about 11 species of Microparsus apparently monoecious on Leguminosae. In North America, populations are usually holocyclic, but Central & South American populations are likey to be partly anholocyclic. Microparsus variabilis (Desmodium aphid) Eastern USA, CanadaMicroparsus variabilis tightly curls the leaves of tick trefoil and lives in the leaf crumples (see first picture below). Adult apterae (see second picture below) are predominantly green to yellow-green, with the head, cauda and small areas around the siphunculi yellow to dark orange. Their antennal tubercles are well developed. The antennae are dark except for the basal 0.60-0.67 of segment III which is pale (cf. Microparsus desmodiorum, which has antennal segment III almost wholly dark). Antennal segment III bears 1 or 2 secondary rhinaria. The legs are pale except for the distal ends of the femora, the proximal and distal tips of the tibiae and all of tarsi, which are dusky to black (cf. Microparsus desmodiorum, whose tibiae are wholly dark). There are small light brown antesiphuncular sclerites encircling the anterior of the siphunculi (cf. Microparsus olivei, which has large black presiphuncular and postsiphuncular sclerites, forming rings around the bases of the siphunculi). The siphunculi are black, the base often appearing slightly lighter than the distal half. The cauda and anal plate are pale yellow to orange. The cauda is swollen at the base, and then tapers to a point; it bears 4 to 5 pairs of lateral hairs plus 0-4 dorsal or dorsolateral hairs. The body length of adult Microparsus variabilis apterae is 1.6-2.0 mm. Immatures are yellowish to pale green.
Images above by permission, copyright Claude Pilon, all rights reserved. The alate Microparsus variabilis vivipara (see third picture above) is similar in colour to the apterous vivipara. Antennal segment III bears 2-6 secondary rhinaria. The forewing of the alata has dark cubital veins and the media vein is often 1-branched. Their hind wings lack oblique veins. Microparsus variabilis lives on two genera of the Fabaceae, namely tick trefoils (Desmodium) and hogpeanuts (Amphicarpaea). On tick trefoil it tightly curls the leaves and lives in the leaf crumples. On hogpeanuts it lives on the stems and undersides of the leaves (Hottes & Frison, 1931). Oviparae and alate males have been found in mid-August. The desmodium aphid is found in eastern USA and Canada.
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