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Brome grass aphidOn this page: Identification & Distribution Other aphids on the same host
Identification & Distribution
Adult apterae of Diuraphis mexicana (see first picture below) are pale yellow-brown to pale green with a pale brown head and appendages, and are wax-powdered. Their antennae are shorter than the body, with the terminal process 0.9-1.25 times the base of antennal segment VI (cf. Diuraphis meuhlei, which has the terminal process 1.2-1.65 times the base, or down to 1.0 in summer dwarfs). The length of hairs on antennal segment III is approximately 0.5 times the diameter of its base (cf. Diuraphis calamagrostis in Europe, which has these hairs only slightly less than the diameter of the base). The rostrum extends to the middle coxae with the apical rostral segment shorter than the second hind tarsal segment (HTII). Abdominal tergites III-V (sometimes also II and VI) have small marginal tubercles (cf. Diuraphis frequens, which has marginal tubercles absent). Abdominal tergite VIII has a short, broadly triangular supracaudal process (cf. Diuraphis noxia & Diuraphis meuhlei, which both have a longer finger-like process on tergite VIII). The siphunculi are short, without an apical flange (cf. Diuraphis mexicana Diuraphis noxia, which has an apical flange on the siphunculi). The cauda is elongate, triangular with a pointed apex, and usually with 4 lateral hairs. The body length of adult Diuraphis mexicana apterae is 1.4-2.0 mm.
Images copyright Frank Peairs, Colorado State University, Bugwood.org under a creative commons licence.
The alate Diuraphis mexicana has antennae shorter than the body, with 4-7 secondary rhinaria distributed in a straight row on antennal segment III, 0-2 on segment IV, and none on segment V. The wings have the veins fuscous bordered. The abdominal dorsum has no scleritized patches or bands.
Colonies of Diuraphis mexicana feed on open or rolled leaves of brome grass (Bromus) species, especially mountain brome (Bromus marginatus), cheat grass (Bromus tectorum) and California brome (Bromus carinatus), as well as on orchard grass (Dactylis glomerata). Aphid colonies may occur on open leaves or within rolled leaves, with feeding damage expressed as yellow streaking on light green leaves. In Mexico and California the species is mainly anholocyclic, but it is thought to be monoecious holocyclic further north (see picture of egg above). Diuraphis mexicana is found in Mexico, Western USA and British Columbia, Canada.
Other aphids on the same host
Diuraphis mexicana has been recorded on 6 Bromus species (Bromus carinatus, Bromus catharticus, Bromus marginatus, Bromus polyanthus, Bromus proximus var genuinus, Bromus tectorum).
Diuraphis mexicana has been recorded on 1 species of Dactylis (Dactylis glomerata)