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Mouse-ear gall aphidOn this page: Identification & Distribution Other aphids on the same host
Identification & Distribution
The aphid Brachycolus cerastii induces pseudogalls on the shoots of mouse ear (Cerastium), especially Cerastium arvense. Leaf margins are thickened and curved inwards to form small, rose-like, yellowish green, oviform or oblong pseudogalls (see picture below) in the shoot tips. The aphids live and feed within these galls.
First image above copyright Mark Wilson under a public domain licence.
Adult apterae of Brachycolus cerastii (see picture above - a few apterae are just visible around the periphery of the gall) are dirty green in colour, and are dusted with white wax powder. The head, antennae, and legs are brown, and the siphunculi are light brown. The antennae are 0.3-0.4 times as long as the body, with a terminal process 2.2-2.7 times as long as the base of antennal segment VI. The apical rostral segment (RIV+V) is about the same length as the second hind tarsal segment (HTII) (cf. Brachycolus stellariae which has RIV+V only 0.55-0.72 times HTII). Abdominal tergite VIII has a small supracaudal process (cf. Brachycolus stellariae. which does not have a supracaudal process). The siphunculi are very short, only 0.01 times body length, and 0.15-0.19 times the cauda (cf. Brachycolus cucubali, which has siphunculi about 0.5 times cauda). The cauda is oblong, triangular, with 5 hairs. The body length of adult Brachycolus cerastii apterae is 1.3-1.7 mm.
Micrographs of clarified mounts by permission of Roger Blackman, copyright AWP all rights reserved.
The alate Brachycolus cerastii (see second picture above) is pale green, with faint marginal sclerites and crossbands on tergites VII & VIII. The antennae are 0.7 times body length, with a terminal process about 3.3 times the base of antennal segment VI. Antennal segment III has about 3-6 secondary rhinaria along one side. The longest hair on segment III is about 0.7 times the basal diameter of that segment.
Brachycolus cerastii is monoecious holocyclic on Cerastium species. Feeding by the aphids causes shoots to be stunted and deformed into gall-like structures. The species is found over most of Europe.
Other aphids on the same host
Brachycolus cerastii has been recorded on 6 species in the Cerastium genus (Cerastium arvense, Cerastium davuricum, Cerastium fontanum, Cerastium glomeratum, Cerastium tianschanicum, Cerastium tomentosum).