InfluentialPoints.com
Biology, images, analysis, design...
Aphids Find them How to ID AphidBlog
"It has long been an axiom of mine that the little things are infinitely the most important" (Sherlock Holmes)

Search this site

Aphididae : Aphidinae : Macrosiphini : Sitobion
 

 

Genus Sitobion

On this page: Sitobion avenae berkemiae fragariae

Genus Sitobion [Macrosiphini]

Sitobion are medium-sized green to dull brownish-green or reddish-brown aphids, with blackish antennae. Their adult viviparae may be winged or wingless. They typically have an intersegmental sclerotic pattern, but some species may have a more or less completely brownish sclerotic dorsal surface. The siphunculi are rather long, blackish and sclerotic, with the apical part reticulated and a small, but distinct flange. The cauda is pale, elongate and finger-shaped from half to nine-tenths as long as siphunculi.

Sitobion is a large genus of over 80 species worldwide. A few species alternate between Rosaceae and grasses, but the majority of species remain on grasses (Poaceae) all year. On grasses they may or may not have a sexual stage. Even within one species, clones may produce males and egg laying females in the autumn - or only produce parthenogenetic females. Sitobion aphids are not attended by ants. At least one species (Sitobion avenae) is a serious pest of cereals.

 

Sitobion avenae (English grain aphid) Europe, North Africa, Middle East, Asia

The adult aptera of Sitobion avenae (see first picture below) is medium-sized and spindle-shaped. It shows colour polymorphism with green and brown forms predominating (immatures are green or red.) The antennae are black and somewhat shorter than the body. The legs are yellow but with the tips of femora, tarsi and tibiae dark. The siphunculi are cylindrical and black and somewhat longer (1.1-1.5 ×) than the pale pointed cauda (cf. Sitobion fragariae which also occurs on grasses, but has its siphunculi 1.7-2.7 × the length of the more rounded cauda). The body length of the aptera is 1.3-3.3 mm. long.

The alate (see second picture above) is 1.6-2.9 mm. long and also occurs in two colour forms - green and brown. It has distinct dark intersegmental markings on the upper surface of the abdomen.

There is no host alternation and the species spends its entire year on cereals and grasses. It occurs on all cereals including rice and maize and can develop on most grasses (Poaceae), as well as on some rushes (Juncaceae) and sedges (Cyperaceae). The majority of the population is anholocyclic (produces only asexual morphs) and overwinters as nymphs or apterae on grasses or winter cereals, but a small proportion of the population is holocyclic (alternates parthenogenetic with sexual reproduction) and overwinters as eggs which hatch in March. Sitobion avenae is widespread throughout the world, with a preference for temperate climates. It occurs widely in Europe, North Africa, the Middle East and Asia.

Read more...

 

Sitobion berkemiae (Bear willow aphid) South-east Asia

Adult apterae of Sitobion berkemiae have a deep green abdomen, a brown head and prothorax and black sclerotic siphunculi. Their antennae are black, six segmented, with a terminal process about 6.6 times as long as the base of antennal segment VI. The apical rostral segment has 4-6 accessory hairs. The dorsum is largely membranous apart from darkened postsiphuncular sclerites. The femora are greenish basally and black distally; the tibiae and tarsi are jet black. The tapering siphunculi are about 1.6 times the length of the cauda. They have a small but distinct flange, and reticulation on the distal 0.32-0.44 of their length (cf. Sitobion berchemiae in China, which have reticulation on the distal 0.25-0.33 of their siphunculi). The cauda is pale yellow-green. The body length of adult Sitobion berkemiae apterae is 1.3-1.8 mm.

Image above by permission, copyright Akihide Koguchi, all rights reserved.

We can find no description of the alate vivipara of Sitobion berkemiae, but it is likely to be similarly coloured to the aptera apart from increased sclerotization on the head and thorax, and possibly black abdominal markings. Immatures (see picture above) are coloured as the adult aptera, except that immature alatae (and probably immature apterae of instars 1-III) have only the distal part of their siphunculi dark.

The only known host of Sitobion berkemiae is bear willow (Berchemia racemosa) in the buckthorn family (Rhamnaceae). They feed along the leaf veins (see picture above). The life cycle of the aphid is unknown. Sitobion berkemiae is only known from Japan.

Read more...

 

Sitobion fragariae (Blackberry-grass aphid) Europe, Asia, South Africa, North & South America

The Sitobion fragariae aptera is dirty yellowish green (see first picture below), with small brown intersegmental sclerites on the abdominal dorsum. The 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 have paler bases on the primary host. They are 1.8-2.7 times longer than the pale pointed cauda (on blackberry cf. Macrosiphum funestum, which has the siphunculi 2.5-3.5 times the length of the cauda; on grass cf. Sitobion avenae, which has the siphunculi 1.1-1.5 times the length of the cauda). The body length of Sitobion fragariae apterae is 1.6-3.0 mm long.

The alates (see second picture above) have a pattern of dorsal dark intersegmental markings that is usually more extensive than in Sitobion avenae.

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. Sitobion fragariae is native to Europe and Asia, but has been introduced to South Africa, North and South America and (probably) Australia and New Zealand.

Read more...

Acknowledgements

Whilst we make every effort to ensure that identifications are correct, we cannot absolutely warranty their accuracy. We have mostly made identifications from high resolution photos of living specimens, along with host plant identity. In the great majority of cases, identifications have been confirmed by microscopic examination of preserved specimens. We have used the keys and species accounts of Blackman & Eastop (1994) and Blackman & Eastop (2006) supplemented with Blackman (1974), Stroyan (1977), Stroyan (1984), Blackman & Eastop (1984), Heie (1980-1995), Dixon & Thieme (2007) and Blackman (2010). We fully acknowledge these authors as the source for the (summarized) taxonomic information we have presented. Any errors in identification or 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

  •  Blackman, R.L. & Eastop, V.F. (2006). Aphids on the world's herbaceous plants and shrubs. Vols 1 and 2. John Wiley & Sons.

  •  Heie, O.E. (1980-1995). The Aphidoidea, Hemiptera, of Fennoscandia and Denmark. (Fauna Entomologica Scandinavica) E.J. Brill, London

  •  Stroyan, H. L. G. (1952). The identification of aphids of economic importance. Plant Pathology 1, 9-14, 42-48, 92-99, 123-129.

 

Identification requests

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!

Bob, InfluentialPoints:

  • 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.