Brachyunguis bonnevillensis

Identification & Distribution

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.

Note: Blackman in Aphids on World Plants says that the records of Brachyunguis bonnevillensis on Atriplex canescens from Remaudiere & Halbert (1969) may in fact be Brachyunguis tetrapteralis. Jensen comments that the species level taxonomy for Brachyunguis in America is 'not fully developed'.

Image copyright CBG Photography Group under a cc by-nc-sa licence.

The main host of Brachyunguis bonnevillensis is black greasewood (Sarcobatus vermiculatus) where it lives in small colonies on leaves, flower stems and new shoots. It has also been found (questionably, see note above) on chamiso (Atriplex canescens). The aphid is assumed to be monoecious holocyclic, and has a dwarf form in summer. Knowlton (1928) notes that the aphid is common in many parts of Utah, attacking the leaves, flower spikes and new tip-growth of its host. 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.

Other aphids on the same host

Brachyunguis bonnevillensis has been recorded on 1 species of Sarcobatus (Sarcobatus vermiculatus).

Blackman & Eastop list 3 species of aphid as feeding on black greasewood (Sarcobatus vermiculatus) worldwide, and provide formal identification keys (Show World list). Of those aphid species, Baker (2015) lists none as occurring in Britain (Show British list).

Brachyunguis bonnevillensis has been recorded on 1 species of Atriplex (Atriplex canescens) (but see note above).

Blackman & Eastop list 3 species of aphid as feeding on chamiso (Atriplex-canescens) worldwide, and provide formal identification keys (Show World list). Of those aphid species, Baker (2015) lists 1 as occurring in Britain (Show British list).

Acknowledgements We are grateful to Andrew Jensen and CBG Photography Group for making their images of Brachyunguis bonnevillensis available for use under creative commons licences. Identification was made by Andrew Jensen by microscopic examination of preserved specimens. We have used the keys and species accounts of Knowlton (1928) and Gillette and Palmer (1932) (as Aphis bonnevillensis), together with information from Roger Blackman & Victor Eastop in Aphids on Worlds Plants. We fully acknowledge these authors and those listed in the reference sections as the source for the (summarized) taxonomic information we have presented. Any errors in information are ours alone, and we would be very grateful for any corrections. For assistance on the terms used for aphid morphology we suggest the figure provided by Blackman & Eastop (2006).

Useful weblinks

References Gillette & M.A. Palmer (1932). The Aphidae of Colorado. Part II. Annals of the Entomological Society of America 25(2), p384 Abstract Knowlton, G. F. (1928). A few western aphids with descriptions of three new species. Annals of the Entomological Society of America 21, 259-268 (p. 262). Abstract Remaudiere, G. & Halbert, S.E. (1996). American species of the genus Brachyunguis Das (Homoptera: Aphididae) Proc. Entomol. Soc. Wash. 98(2), 249-255. Full text