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Marsh marigold aphidOn this page: Identification & Distribution Biology & Ecology
Identification & Distribution:
Rhopalosiphoninus calthae (Marsh marigold aphid)Apterae of Rhopalosiphoninus calthae are shining brownish black. The siphunculi are black and strongly swollen, and 3.5-4.6 times the length of the cauda. Immatures have wax deposits especially over the anterior part of the aphid.
The clarified slide mounts below are of adult viviparous female Rhopalosiphoninus calthae : wingless, and winged.
The marsh marigold aphid does not host alternate. It feeds on the underside of leaves of marsh marigold (Caltha palustris), especially those growing in the shade. Sexual forms occur in autumn.
Biology & Ecology:
Large colonies may develop with aphids covering most of the leaves.
We have recorded syrphid larvae predating Rhopalosiphoninus calthae on marsh marigold (see picture below). Ali et al. (2009) found that the syrphid Ischidon scutellaris was an especially efficient predator of aphids on water plants.
The function of the enormous swelling of the siphunculi, a feature this species shares with the polyphagous Rhopalosiphoninus latysiphon and a few other species, is still unknown (Heie, 2009 ).