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Gooseberry - willowherb aphidOn this page: Identification & Distribution Biology & Ecology
Identification & Distribution:Aphis grossulariae is a dull green to dark green species which is moderately wax powdered. The abdominal dorsum is entirely membranous or at most has narrow dusky bands across tergites 7 & 8. The siphunculi and legs are pale except for the tibial apices and tarsi which are dusky. The antennae are shorter than the body. The body length of apterae is 1.2-2.1 mm.
Aphis grossulariae has marginal tubercles present (see first micrograph below) on at least some of abdominal tergites 2-6. The longest tibial hairs are greater than the least width of the hind tibia. The hairs on the third antennal segment are at most 1-2 times the least width of that segment.
The species is closely related, and very similar to, another species Aphis schneideri that mainly occurs on blackcurrant. In Aphis grossulariae the hairs on the third antennal segment are straight or curved, and are mostly directed apically at various angles (see second micrograph above). In Aphis schneideri the antennal hairs are fine and wavy and conspicuously erect. In Europe there is evidence of natural hybridisation with Aphis schneideri (Rakauskas 2003 ).
The clarified slide mounts below are of adult viviparous female Aphis grossulariae : wingless, and winged.
The gooseberry - willowherb aphid host alternates between gooseberry (Ribes uva-crispa) where it curls the leaves and willowherb (Epilobium spp.). Sexual forms occur in autumn. It occurs throughout most of Europe to Russia and central Asia.
Biology & Ecology:
The eggs of Aphis grossulariae laid on gooseberry the previous autumn hatch in March and early April the following year.
The developing aphids then feed on the fruit buds and then the tips of young shoots where large colonies may develop.
Colonies of the gooseberry-willowherb aphid are often, but not always attended by ants. Despite the attentions of ants such as Lasius, the aphid may be subject to high rates of parasitism especially by Lysiphlebus confusus (Starý & Havelka, 2008 ).
Lysiphlebus confusus appears to possess specific adaptations, chemical and behavioural, that negate the aggressive responses of various ant species (Völkl & Mackauer, 1993 ). Evidence of ant mimicry by the closely related Lysiphlebus fabarum which parasitizes Aphis fabae was presented by Rasekh et al. (2010) . They showed that the parasitoid used ant-like antennation to reduce Aphis fabae defensive behaviour, and their attacks primed Aphis fabae to be more responsive to subsequent honeydew solicitation from both ants and the parasitoids themselves.
Some colonies of Aphis grossulariae remain on gooseberry all year round but there is also some migration to the secondary hosts. These are the smaller willowherb species such as Epilobium montanum and Epilobium lanceolatum. The picture below shows a colony of Aphis grossulariae on Epilobium montanum.
It lives on the stem and flower heads of willowherb often forming mixed species colonies with Aphis epilobii. We have not yet observed any predators on the secondary host, but Gilbert (2005) notes that Aphis grossulariae is a preferred prey of the larvae of Episyrphus balteatus on willowherb.