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Marsh marigold aphidOn this page: Identification & Distribution Biology & Ecology Other aphids on the same host
Identification & Distribution:
Apterae of Rhopalosiphoninus calthae are shining brownish black. The antennae are dark except for the basal part of segment III, and the legs are yellowish. The dorsum has an almost complete black sclerotic shield. The black siphunculi have a narrow, almost cylindrical stem, which widens abruptly to the swollen half which is about 3 times thicker than the narrower part of the stem. The siphunculi are 3.5-4.6 times the length of the cauda.
Alatae have a large black dorsal abdominal patch and strongly swollen siphunculi like the apterae. Immatures have wax deposits, especially over their anterior part.
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. The male is small, black and apterous, and the ovipara lacks the sclerotic tergum and has slightly swollen hind tibiae. Rhopalosiphoninus calthae is found over most of Europe.
Biology & Ecology:
Large Rhopalosiphoninus calthae colonies may develop, with aphids covering most of the leaves.
Many of the immatures in this colony were alatoid - in other words they were destined to develop into alates, and then migrate to other host plants.
We have recorded syrphid larvae predating Rhopalosiphoninus calthae on marsh marigold (see picture above). Ali et al. (2009) found that the syrphid Ischidon scutellaris was an especially efficient predator of aphids on water plants.
Other aphids on same host:
Rhopalosiphoninus calthae has been recorded from 1 Caltha species (Caltha palustris), but also from Aconitum leucostomum.