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Brachyunguis aphids are usually grey or green and, apart from the North American species, are often coated with mealy wax. They are generally without body sclerotization, apart sometimes from darkening of the head, and the presence of small marginal sclerites on the thoracic tergites and separate sclerites on the 7-8th abdominal tergites. The clypeus is often globose, but the extent of its enlargement varies considerably. The antennal terminal process is usually shorter, but is occasionally equal to or slightly longer, than the base of the apical antennal segment. Secondary rhinaria are absent in the apterous viviparous females. In the majority of species the apical rostral segment is shorter than the second segment of hind tarsus; it is rarely equal to or a little longer than it. The first tarsal segments have 3:3:2 hairs. The siphunculi are very short, pale or rarely dark, and subcylindrical or conical. The cauda is conical, triangular, or finger-shaped, and is pale or dark, with 6-12 hairs. The genus has been divided into the subgenera Brachyunguis s. str. and Xerophilaphis, but the justification for this has been challenged (see Blackman in Aphids on World's Plants).
Brachyunguis has about 40 species which feed mostly on plants in the Amaranthaceae (= Chenopodiaceae), but have also been found on various other families including the Apiaceae, Asclepiadaceae, Asteraceae, Brassicaceae, Cuscutaceae, Pistaceae, Polygonaceae, Sapindaceae, Solanaceae and Zygophyllaceae. The species of Brachyunguis are distributed in arid regions of Southern Europe, Northern Africa, Asia, and America. Kadyrbekov (2001) gave a brief diagnosis of the genus in his description of xerobiont taxa from the subtribe Aphidina.
Brachyunguis bonnevillensis (Frosty greasewood aphid) North America
Adult apterae of Brachyunguis bonnevillensis are pale bluish green, with a "frosty appearance" (cf. Brachyunguis bishopi, also on Sarcocarpus vermiculatus in western USA, which is a dark pea green). Antennae, legs and siphunculi are pale. The terminal process of the antenna is 0.7-1.0 times as long as the base of antennal segment VI (cf. Brachyunguis tetrapteralis, also on Atriplex canescens in western USA, which has the terminal process 1.3-1.8 times the length of the base). The longest hairs on antennal segment III are 8-14 µm. The rostrum is obtuse, slender, and reaches the third pair of coxae, and the apical rostral segment (RIV+V) is 0.9-1.2 times the length of the second hind tarsal segment (HTII) (cf. Brachyunguis tetrapteralis which has RIV+V 1.3-1.8 times the length of HTII). Marginal tubercles are present on abdominal tergites I & VII, but absent on abdominal tergites II-V (cf. Brachyunguis bishopi, which has marginal tubercles present on one or more of tergites II-V). The siphunculi are cylindrical or slightly swollen near the distal end, constricted before the flange, and 0.4-0.8 times the caudal length (cf. Brachyunguis bishopi, which has siphunculi 0.7-1.25 times the length of the cauda). The cauda is long-conical with a tendency to constriction near its base, and bears 4 hairs on each side (2-3 hairs in dwarf form). The body length of adult Brachyunguis bonnevillensis apterae is 1.0-2.1 mm.
The alate Brachyunguis bonnevillensis has a shiny black head and thorax, and a blue-green to yellow-green abdomen with pale appendages. There are 4-8 circular secondary rhinaria arranged in a row along most of antennal segment III; they are absent in apterae.
The main host of Brachyunguis bonnevillensis is black greasewood (Sarcobatus vermiculatus) where it lives in small colonies on leaves, flower stems and new shoots. The aphid is assumed to be monoecious holocyclic, and has a dwarf form in summer. The apterae are so much the color of the fleshy leaves that they are often overlooked unless a careful examination is made. They usually lie very quietly against the fleshy leaves of the plant. Ants are seldom found associated with this aphid. It is distributed throughout western USA into Mexico.
Brachyunguis tamaricis (Common tamarisk aphid) Europe, North Africa, Asia
Adult apterae of Brachyunguis tamaricis are light green with a reddish area around the siphuncular bases (see first picture below). They have a rather patchy coverage of light grey wax, which gives them a velvety grey-green appearance and obscures the reddish patches around the siphunculi. Their antennae are 5- or 6-segmented. When 6-segmented, antennal segment III is about as long as antennal segment VI or shorter (cf. Brachyunguis tamaricophilus which, when the antennae are 6-segmented, has antennal segment III much longer than segment VI). The apical rostral segment (R IV+V) is 0.6-0.75 times as long as the second hind tarsal segment (HT II) (cf. Brachyunguis tamaricophilus, for which R IV+V is 0.8-0.9 times the length of HT II). The siphunculi of Brachyunguis tamaricis are rather short, only 0.63-1.0 times as long as the cauda. The cauda is finger-like (cf. Brachyunguis tamaricophilus, which has a triangular cauda). The body length of adult Brachyunguis tamaricis apterae is 0.9-1.7 mm.
Images above copyright Dr László Érsek, all rights reserved.
The alate Brachyunguis tamaricis may be less heavily waxed than the aptera (see second picture above). They have 2-8 secondary rhinaria on antennal segment III, 0-2 on segment IV and 0-1 on segment V.
Brachyunguis tamaricis feed only on tamarisk (Tamarix species). Sexual forms (oviparae and apterous males) have been recorded in Europe (France & Portugal) in autumn. They may be attended by ants. Brachyunguis tamaricis occurs in south, central and eastern Europe (not in Britain), North Africa and south-west and central Asia.