CYLAS FORMICARIUS PDF

Top of page Eggs are laid singly in cavities in the root or stems. Following egg deposition the egg hole is covered with a greyish mass which hardens to form a protective cap over the developing egg Reinhard, ; Gonzales, Cockerham et al. Larvae feed inside roots or stems where oviposition occurs for days during which they complete three larval instars Sherman and Tamashiro, Mullen found a larval development period of Gonzales found a larval period of 25 days under Philippines field conditions while Cockerham et al.

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Top of page Eggs are laid singly in cavities in the root or stems. Following egg deposition the egg hole is covered with a greyish mass which hardens to form a protective cap over the developing egg Reinhard, ; Gonzales, Cockerham et al. Larvae feed inside roots or stems where oviposition occurs for days during which they complete three larval instars Sherman and Tamashiro, Mullen found a larval development period of Gonzales found a larval period of 25 days under Philippines field conditions while Cockerham et al.

Pupation takes place within the sweet potato roots or stems where larvae feed. The mature larva excavates a cell 2 to 3 times the size of its body in which pupation occurs. The pupal period lasts days Franssen, ; Sherman and Tamashiro, In a laboratory study, Mullen found pupal period duration from 5 to Soon after emergence from the pupa, the adult stays in the pupal chamber and then cuts its way through the plant tissue.

Adults mate soon after emergence but oviposition does not occur for a minimum of 4. Reinhard , Subramanian and Jayaramaiah reported similar preoviposition periods.

Males have a greater flight ability than females of all ages and are more active in the field. No distinct migratory behaviour of adults has been detected.

Flight activity of males peaked just after the onset of darkness in laboratory studies, and gradually decreased toward the onset of light. Females disperse mainly by walking because of their low flight ability Moriya and Hiroyoshi, Walking activity in both sexes is also greatest in the dark Shimizu and Moriya, b.

Adults feign death as a predator avoidance strategy. Males are attracted to a sex pheromone released by females Coffelt et al. Females in the laboratory can mate repeatedly for 40 days after eclosion, but in the field females rarely remate because secretion of the sex pheromone is inhibited after the first mating Sugimoto et al.

Adult weevils are attracted to sweet potato foliage and tubers by plant odour Nottingham et al. An oviposition stimulant, identified as boehmeryl acetate a pentacyclic triterpenoid , has been identified from the periderm of tubers. This compound, which increased oviposition in root core bioassays, was found in greater quantities in susceptible lines of sweet potato. Fecundity varies greatly. Mullen reported the mean generation duration from egg to egg of Subramanian recorded life cycle duration of days under undefined conditions.

Adult survival varies greatly. Franssen in Indonesia reported females to survive a maximum of days. Gonzales in the Philippines reported that males survived days and females days. Subramanian found males and females surviving for 94 and days, respectively, in India. Natural enemies.

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Cylas Formicarius

Introduction Back to Top Sweetpotato weevil is the most serious pest of sweet potato, not only in the United States, but around the world. It causes damage in the field, in storage, and is of quarantine significance. It is inherently of interest to entomologists due to its strikingly colorful appearance and extremely long rostrum beak. Figure 1. Larvae of sweetpotato weevil, Cylas formicarius Fabricius.

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Cylas formicarius

Overview Origin The origin of Cylas formicarius is not definitely known, but it is thought it may have originated in Africa or India. Life Cycle Adults are ant-like, shiny, blue-black, snout beetles whose "waist" and legs are bright orange-red. They are about 0. Larvae are legless, white to cream colored with a pale brown head. Larvae are about 0. Breeding is continuous throughout the winter, especially in potatoes in storage.

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