Cactoblastis cactorum

Cactoblastis cactorum, the cactus moth, South American cactus moth or nopal moth, is native to Argentina, Paraguay, Uruguay and southern Brazil. It is one of five species in the genus Cactoblastis that inhabit South America, where many parasitoids and pathogens control the expansion of the moths' population. This species has been introduced into many areas outside its natural range, including Australia, the Caribbean, and South Africa. In some locations, it has spread uncontrollably and was consequently classified an invasive species. However, in other places such as Australia, it has gained favor for its role in the biological control of cacti from the genus Opuntia, such as prickly pear. In South America, Cactoblastis cactorum has many natural predators, including ants and New World monkeys. Ants, the moths' main predators, consume its larvae. New World monkeys dig the larvae and pupae out from the flattened leaf-like stems, or 'cladodes', of the cacti. The relationship between Cactoblastis cactorum and Opuntia cactus species is parasitic: the moth feeds on the host cactus. Recent work in South America has identified four genetically-structured ecotypes of C. cactorum that infest different hosts and possess different larval morphology. The mechanism driving this isolation and pattern of host-association in the field remains unexplored. Adults of Cactoblastis cactorum are nondescript brownish-gray moths with long legs and long antennae. The moth can be identified only by a microscopic examination of dissected male genitalia. They generally appear as typical Pyralidae, with the pronounced labial palps of the female, thus the name 'snout moths'. The forewings show a characteristic banding pattern similar to other related moths. The hindwings are whitish and semitransparent, and the wingspan of adult moths varies by age and sex. The average wingspan is 27–40 mm for females, and 23–32 mm for males. The larvae of C. cactorum are caterpillars that start out with a pink-cream color and gradually become orange, with distinctive black spots or bands. Cactoblastis cactorum mating occurs before sunrise. Mates are found by scent rather than sight. Once a female finds a mate, she begins to release sex pheromones that signal to males her readiness. When the male responds, the mating process is initiated. The initial process of mating begins when the female and male attach themselves at their abdomens. The male passes a sac, known as the 'spermatophore', and the female stores the sac in her abdomen's reproductive center. After an incubation period, the female deposits an 'egg stick' that contains 30–50 eggs. The eggs are laid on either the tip of the cactus spine, the cactus leaf, the cladode, or the cactus fruit. Egg sticks that resemble cactus spines develop and hatch in 25–30 days. The gregarious larvae bore into the cactus pad through a single entry hole by chewing through the tough outer cuticle of the cladode. The external damage that results is characterized by yellowed plant tissue with plant fluid ooze and insect frass. The larvae feed inside the cactus and eventually hollow out the cactus pad, consuming everything but the vascular tissues.