Image of a Cactus Moth hanging off of a plant
- Mature larvae are 25-30 mm long
- Wing span of adults ranges from 22 to 35 mm
- Forewings are grayish-brown, but whiter toward coastal margin
- Distinct antemedial and subterminal lines
- Hindwings white with some gray terminally
- Phycitine adults are often very similar, but can be identified by genitalia
- Larvae are bright orange/red with large dark spots forming transverse bands
The discovery of the Cactus Moth, Cactoblastis cactorum, in the Florida Keys in October, 1989 raised the number of phycitine moth species associated with prickly pear cacti (Opuntia spp.) in Florida by at least five times. The moth's range has continued to expand along both the Atlantic and Gulf coasts. It is now found as far north as Charleston, SC and as far west as Piney Island and the St. Mark's Wildlife Refuge south of Tallahassee, FL.
The female lays its eggs in the form of a chain, the first egg is attached to the end of a spine or spicule and succeeding eggs (140 or more, average is 75) stacked coin-like to form an egg-stick. On eclosion, the larvae crawl from the egg-stick onto the cladode or pad and burrow into it, usually within a few centimeters of the oviposition site. The larvae feed gregariously moving from cladode to cladode as the food supply is exhausted. During feeding the grass is pushed out of the pad and forms a noticeable heap on the ground. Fully developed larvae usually leave the plant and spin white cocoons in the leaf litter, in crevices in the bark of nearby trees, or in similar protected niches. Pupation occasionally occurs in the cladode. The moth emerges and the cycle is repeated. The length of the life cycle in Florida is unknown but probably shorter than in Queensland, Australia, where there are two generations per year.
Portions of this article courtesy of: Cactus Moth