Rodolia cardinalis

Identification

Rodolia cardinalis is a rather small ladybird, about 2.5-4 mm long, which is covered with dense, short hairs. The elytra are reddish brown with a total of five black spots, two on each elytron and one on the suture, extending down the suture to the posterior edge (see first picture below). These spots are often merged together to form an irregular black patch (see second picture below). The head, most of the prothorax and the scutellum of Rodolia cardinalis are black, while the legs and antennae are mainly reddish.

First images above copyright Maurice under a Creative Commons Attribution-Share Alike 2.0 Generic License.
Second image above copyright Katja Schulz under a Creative Commons Attribution-Share Alike 2.0 Generic License.
Third image above copyright Hectonichus under a Creative Commons Attribution-Share Alike 3.0 Unported License.

The fourth instar larva of Rodolia cardinalis (see third picture above) is about 5 mm long. The body is orange-red to reddish purple The dorsal and dorso-lateral tubercles are black, but the ventro-lateral tubercles are reddish. All tubercles bear short bristles. The prothorax and head are red.

Biological control & Distribution

Rodolia cardinalis generally has a very narrow host-range, being restricted to just a few species of scale insects in the Coccidae (soft scales) and Margarodidae (cottony cushion scales). However, if its usual prey are scarce, it may take other scale insects, aphids, mites, etcetera. The Vedalia beetle is native to Australia, but now has a world wide distribution due to its widespread use in classical biological control operations against (primarily) the cottony cushion scale (Icerya purchasi). As such it has proved invaluable in classical biological control operations outside its natural range, the first such operation being its introduction to California in the late 19th century for control of cottony cushion scale on citrus (see Caltagirone & Doutt (2004)). It is mostly found in warmer climates, but has been found in cooler climes (see for example Salisbury & Booth (2004) who found it feeding on Icerya purchasi in London gardens).

Image above of Rodolia cardinalis feeding on Icerya purchasi, copyright M. Heber under a Creative Commons Attribution-Share Alike 3.0 Unported License.

Acknowledgements For coccinellid identification we have used Hackston for the key characteristics, together with the latest Wikipediaaccount for each species. For aphids we have made provisional identifications from photos of living specimens, along with host plant identity using 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 Caltagirone, L.E. & Doutt, R.L. (1989). The history of the vedalia beetle importation to California and its impact on the development of biological control. Annual Review of Entomology 34, 1-16. Abstract Salisbury, A. & Booth, R.G. (2004). Rodolia cardinalis (Mulsant), the Vedalia ladybird (Coleoptera: Coccinellidae) feeding on Icerya purchasi Maskell, Cottony cushion scale (Hemiptera: Margarodidae) in London gardens. British Journal of Entomology and Natural History 40(1), 75-83. Full text