Australian’s are well known for seizing an opportunity when in foreign lands, but is that the case for this new arrival in New Zealand?

by Stephen Thorpe (stephen_thorpe@yahoo.co.nz)

Research Associate, University of Auckland

Rodolia koebelei (Coleoptera: Coccinellidae) is a fairly distinctive looking ladybird, about 3 mm in length. The extent of black markings on the elytra varies from none to that shown in the photo. This Australian species was reported as validated new to New Zealand by Biosecurity New Zealand (2006). Nobody knows how it got here. On 19 February 2015, I found a single specimen, on a cultivated Hebe, on the Tamaki Campus. So far, this is the only specimen I have seen on campus, and I have only ever seen two others elsewhere in Auckland, though one of those two was at the adjacent Morrin Reserve. Very little is known about this species in New Zealand. In particular, mystery surrounds what it preys on. According to one overseas study, larvae of R. koebelei could only be reared to adults on Icerya koebelei and when they were offered other species of scale insect (I. purchasii, I. aegyptiaca, or I. seychellarum), they failed to feed and all died (Sands & Van Driesche, 2004). The mystery is that I. koebelei is not known to be present in New Zealand. Perhaps it actually does prey on the closely related cottony cushion scale (I. purchasi), which is present on campus. If so, this is evidence that the results of host range testing experiments need to be treated with caution. At any rate, there is plenty of scope for further research on this ladybird in Auckland. Larvae need to be located, and the likely prey needs to be determined. The species could potentially be useful as a biocontrol agent for cottony cushion scale, in the same way as the cardinal ladybird (Rodolia cardinalis), the latter of which now appears to be very rare in Auckland (I haven’t seen any on campus).

REFERENCES
Biosecurity New Zealand 2006: Biosecurity magazine, (68) http://www.biosecurity.govt.nz/files/publications/biosecurity-magazine/issue-68/biosecurity-68.pdf

Sands, D.P.A.; Van Driesche, R.G. 2004: Using the scientific literature to estimate the host range of a biological control agent. Pp. 15-23 in: Van Driesche, R.G., Murray, T. & Reardon, R. (eds.), Assessing host ranges of parasitoids and predators used for classical biological control: a guide to best practice. Morgantown, W. Va.: Forest Health Technology Enterprise Team, U.S. Dept. of Agriculture, Forest Service. http://www.invasive.org/hostrange/ch3.pdf