Identification & Distribution:
The adult aptera of Sitobion fragariae is spindle-shaped and a dirty yellowish green, with small brown intersegmental sclerites on the abdominal dorsum (see first picture below on primary host, second picture below on secondary host). Their antennae are about the same length as the body, with the basal segments paler than the rest. The siphunculi are usually entirely black (although they may be paler on the primary host) and are 1.7-2.7 times longer than the pale cauda. (On blackberry cf. Macrosiphum funestum which has the siphunculi 2.5-3.5 times longer than the cauda. On grasses cf. Sitobion avenae which has the siphunculi 1.1-1.4 times longer than the cauda). The body length of Sitobion fragariae apterae is 1.6-3.0 mm long.
Alatae (see picture below) have a pattern of dorsal dark intersegmental marking more extensive than those on Sitobion avenae.
The first two clarified slide mounts below are of adult viviparous female Sitobion fragariae (on their primary host) : wingless, and winged.
Micrographs of clarified mounts by permission of Roger Blackman, copyright AWP all rights reserved.
The second two clarified slide mounts above are of adult viviparous female Sitobion fragariae (on their secondary host) : wingless, and winged.
The blackberry - grass aphid host alternates from blackberry (Rubus fruticosus agg.) and occasionally other Rosaceae to grasses (Poaceae) especially Holcus spp. and some sedges (Carex spp). Sitobion fragariae eggs hatch in spring and the young nymphs feed on the breaking buds. Colonies build up, and in summer alates migrate to cereals and grasses. A return migration takes place in autumn.
Other aphids on same host:
- Blackman & Eastop list 23 species of aphid as feeding on 'Yorkshire fog' (Holcus lanatus) worldwide, and provide formal identification keys.
Of those aphid species, Baker (2015) lists 22 as occurring in Britain:
- Blackman & Eastop list 11 species of aphid as feeding on 'creeping soft grass' (Holcus mollis) worldwide, and provide formal identification keys.
Of those aphid species, Baker (2015) lists all 11 as occurring in Britain:
David Fenwick, 10 June 14
Have an interesting aphid for you, what appears to be a Sitobion. It
was found on Wall Barley, Hordeum murinum, on a small pier at Newlyn
today. 10.06.14. SW 46490 28497. Juveniles quite orange in colour.
Few adults, mostly juveniles on each inflorescence, grass also looked
like it was going over, becoming dry and purplish.
Hope I have the right genus.
Image(s) copyright www.aphotofauna.com all rights reserved.
Think I have it, Sitobion avenae!
A variable little beastie!
I know it can be rather variable, but I'm not convinced it is Sitobian avenae.
Even allowing for foreshortening due to perspective, the siphunculi are too long relative to the cauda. (S. avenae siphunculi are no more than 1.4 times the length of the cauda.)
Given the host and the dark siphunculi, it is much more likely to be Sitobion fragariae, whose siphunculi are at least twice the length of the cauda.