Cactoblastis cactorum (Berg, 1885)
Prickly Pear Moth
(previously known as Zophodia cactorum)
PHYCITINI ,   PHYCITINAE ,   PYRALIDAE ,   PYRALOIDEA
 
Don Herbison-Evans
(donherbisonevans@outlook.com)
and
Pat and Mike Coupar
and
Stella Crossley

Cactoblastis cactorum
young caterpillar, magnified
(Photo: Don Herbison-Evans, Bundaberg, Queensland)

The Caterpillars of this moth feed on the pads (cladodes) of the several pest species of Opuntia that were unfortunately introduced into Australia, especially including:

  • Prickly Pear ( Opuntia stricta CACTACEAE ).

    Cactoblastis cactorum
    older caterpillars
    (Photo: Don Herbison-Evans, Bundaberg, Queensland)

    The Caterpillars live and feed communally inside the tough leathery (and prickly) skin of the host plant, reducing the plant material inside to a gooey green mess. The Caterpillars are initially pinkish-cream coloured, with dark red dots on the back of each segment. Later instars become orange, and the dots expand and then fuse to become a dark band across each segment. The Caterpillars grow to length of about 1.5 cms.

    Cactoblastis cactorum
    (Photo: Don Herbison-Evans, Bundaberg, Queensland)

    They normally pupate in white cocoons amongst the ground debris. In captivity, some pupated at the top of their jar, and some at the bottom.


    (Photo: Don Herbison-Evans, Bundaberg, Queensland)

    The adult is fawn with faint dark dots and lines on the wings, and has a long nose. The moth normally rests with its wings wrapped around its body. The moth has a wingspan of about 2 cms.

    Cactoblastis cactorum
    (Specimen: courtesy of the Macleay Museum, University of Sydney)

    The species was originally found in Argentina, but was introduced to Australia in 1926 by the release of 2,000,000 eggs near the town of Chinchilla, in order to control the Prickly Pear which was overtaking much of Queenland. For the same reason, the species has been introduced into other countries, including:

  • Caribbean Islands,
  • Hawaii, and
  • South Africa.


    mating pair of adult moths
    (Photo: Don Herbison-Evans, Bundaberg, Queensland)

    The species is now common over

  • Queensland,
  • New South Wales, and
  • South Australia,
    and the Prickly Pear has been reduced to isolated plants of little economic significance.

    Unfortunately, the moth has also spread to the mainland of north America, and has become a pest there on the local cacti.


    egg pile on a cactus spine
    (Photo: Don Herbison-Evans, Bundaberg, Queensland)

    The eggs are laid on top of each other like a stack of coins, the first one being anchored to a cactus spine. The stack can contain over 100 eggs, and curves over to make a kind of bent stick with a length of up to 2 cms. When they hatch, the young caterpillars walk down the stick and start burrowing into the cactus.

    Cactoblastis cactorum
    Ascension Island, 1998


    Further reading :

    Cárlos Berg,
    Quindecim Lepidoptera nova faunae Reipublicae Argentinae et Uruguayensis,
    Annales Societe Ciencias Argentina,
    Volume 6, Part 19 (1885), p. 276.

    Ian F.B. Common,
    Moths of Australia,
    Melbourne University Press, 1990, fig. 32.3, pl. 25.14, pp. 58, 72, 349.

    Paul Zborowski and Ted Edwards,
    A Guide to Australian Moths,
    CSIRO Publishing, 2007, pp. 28, 128.


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    (updated 19 October 2010)