The adult of M. semipunctatum is a wingless, black beetle with a convex, often elongate, dull to shining, glabrous body. Females are 15Ð30 mm long and males 15Ð26 mm long. M. semipunctatum has small pronotal spines, large punctures on the disk of the pronotum, and a lack of pubescent patches on the coxae. There are some geographical variations in morphology, in northern populations, punctuation of the pronotum is denser and the integument is often duller than in southern populations (Linsley and Chemsak, 1984).
Related crop
- Opuntia
Related Farm Practice
- Feeding
- Hosts
- Activity
- Services
Adults feed on the succulent portions of cacti and the larvae feed near the root collar and within the stems. Feeding activity by boring larvae of M. semipunctatum on Opuntia can be recognized above ground by the tar-like excrement of the larvae and the fluids expelled by the plant from the wounds they create (Evans and Hogue, 2006). Adult feeding by Moneilema spp. can often result in severance of the joints in Opuntia, which fall to the ground and frequently take root, aiding dissemination of the plants. Heavy infestations of the beetles can kill the plants (Woodruff, 1966). Although M. semipunctatum is not generally lethal for Opuntia plants, which can propagate vegetatively, the effect of the beetle on Sclerocactus varies with the host species (Woodruff, 2010). Infestation by M. semipunctatum has been reported as a significant but localized source of mortality of all Sclerocactus species on the Colorado Plateau, particularly of larger, mature, reproducing individuals (Utah Ecological Services Field Office, 2010).