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Rhopalosiphoninus calthae

Marsh marigold aphid

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 dorsum has an almost complete black sclerotic shield.

The clarified slide mounts below are of adult viviparous female Rhopalosiphoninus calthae : wingless, and winged.

 

Micrographs of clarified mounts  by permission of Roger Blackman, copyright AWP  all rights reserved.

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 ).

Acknowledgements

Our particular thanks to Roger Blackman for images of his clarified slide mounts.

We have made provisional 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

  •  Ali, A.et al. (2009). On the predation of aphids by Ischiodon scutellaris (Diptera: Syrphidae) under natural environment. Bionotes 11 (3), 95-96.Full text 

  •  Heie, O.E. (2009). Aphid mysteries not yet solved/Hemiptera:Aphidomorpha. Monograph: Aphids and other hemipterous insects 15, 31-48.  Full text