Sweetpotato weevil, Cyclas formicarius elegantulus (Summers)(Coleoptera: Curculionidae). Photo by J. V. Robinson.
Common Name: Sweetpotato weevil
Scientific Name: Cyclas formicarius elegantulus (Summers)
Order: Coleoptera
Description: The adult is about 1/4 inch long, shiny and slender bodied for a weevil, appearing almost ant-like. The middle of the body (prothorax) and the legs are red and the rest of the body is blue-black. Larvae are elongate but slightly C-shaped in appearance, legless and dirty white to gray in color with a distinct head capsule that is yellow-brown in color. Few other weevils would be confused with sweetpotato weevil.
Life Cycle:The life cycle can continue throughout the year in stored sweet potatoes. All stages may be found almost anytime. Eggs are deposited singly in a small cavity that the female eats in stems or sweet potatoes or in cracks or crevices. Larvae hatch in about a week and take 2 to 3 weeks to develop through several stages (instars) in good conditions. A generation takes about one month to 6 weeks. Adults can fly well with reports of over a mile and they may live up to 8 months.
Habitat and Food Source(s): Mouthparts are for chewing. Found on sweet potatoes in the field and in storage. Larvae tunnel into tubers and stems. They probably also feed on related plants like morning glory.
Pest Status: A pest of sweet potatoes because the larvae tunnel into tubers, attacking living plants in the field and continuing to develop in stored sweet potatoes; damaged tubers develop a bitter taste and a bad odor; primarily found in east Texas and quarantine laws limit the distribution of sweet potatoes; medically harmless.
For additional information, contact your local Texas A&M AgriLife Extension Service agent or search for other state Extension offices.
Literature: Metcalf et al. 1962; Peterson 1951.