Palm Weevil

Curculionidae, Curculioninae,

Rhynchophorus palmarum. Spanish:

Mayate prieto (Mexico). Portuguese-.

Aramandaia (Brazil).

One of the world's largest weevils (BL 3-4.9 cm) (fig. 9.16b), the palm weevil frequently draws attention when seen crawling on the trunks of its palm hosts. It is completely shiny black and has a snout about as long as the body is wide and strongly grooved wing covers that are slightly shorter than the abdomen. It is a powerful insect and difficult to dislodge from objects it grasps.

The species is well known throughout Latin America as a depredator of coconut palms, by direct feeding and as a vector of the injurious red-ring nematode (Rhadina-pelenchus cocophilus) in many parts of its range (Griffith 1987). Females place their eggs, one at a time, in an incision made with the beak at the base of the leaf rachis and in stems. The larvae (fig. 9.16c) bore in via the opening and eventually become large (BL 45—60 mm), fat, white, curved grubs with a short fusiform tail and large mahogany brown head. The back plate of the first thoracic segment is small. They develop while mining in the trunk usually of sick or dead trees but also in young, healthy trees, often killing them. The species is considered the most destructive pest of coconut palms in the West Indies and Central America (Wilson 1963). It is also linked with red-ring viral disease and nematode pests. Pupation occurs on the exterior of stems and leaves in a cocoon made of interlacing fibers cut from the interior of the stem; the larva draws these tightly around itself before pupating. A fair amount is known about its biology because of its economic importance (González and Camino 1974, Hagley 1965). Stages overlap in development time, and it »s possible to find all in one tree or any at all times of the year. The total life cycle varies greatly, requiring from 30 to 100 days.

This weevil uses many other palms as hosts, such as palmetto palms (Sabal), Acrocomia, Attalea, Mauritia, and oil palm (Elaeis guineensis), on which it is considered a pest. It also feeds on other plants with fibrous stems such as papaya, large grasses (iGynerium), and sugarcane. It usually develops within young plants, from which it has traditionally been harvested as a food item by natives. These food larvae, called suri in the Peruvian Amazon and grou-grou (or gru-gru) elsewhere, may be eaten raw but are more usually fried in a pan with oil and salt (Cowan 1865: 69, DeFoliart 1990, orig. obs.).

A related and similar species, Rhynchophorus cruentatus is also a plant pest in Latin America (Wattanapongsiru 1966). This and the palm weevil have been reared in the laboratory (Giblin-Davis et al. 1989).

References

Cowan, F. 1865. Curious facts in the history of insects. Lippincott, Philadelphia. DeFoliart, G. 1990. Hypothesizing about palm weevil and palm rhinoceros beetle larvae as traditional cuisine, tropical waste recycling, and pest and disease control on coconut and other palms. Food Ins. Newsl. 3: 1,3,4,6. Giblin-Davis, R. M., K. Gerber, and R. Griffith. 1989. Laboratory rearing of Rhynchophorus cruentatus and R. palmarum (Coleoptera: Curculionnidae). Fía. Entomol. 72: 480-488. González, A., and M. Camino. 1974. Biología y hábitos del mayate prieto de la palma de coco, Rhynchophorus palmarum (L.), en la Chontalpa, Tab. Fol. Entomol. Mexicana 28: 13-19. Griffith, R. 1987. Red ring disease of coconut palm. Plant Dis. 71: 193-196. Hagley, E. A. C. 1965. On the life history and habits of the palm weevil, Rhychophorus pal-manum. Entomol. Soc. Amer. Ann. 58: 22-28. Wattanapongsiru, A. 1966. A revision of the genera Rhynchophorus and Dynamis (Coleoptera: Curculionidae). Dept. Agrie. Sci. Bull. (Bangkok) 1: 1-328. Wilson, M. E. 1963. Investigations into the development of the palm weevil Rhynchophorus palmarum (L.). Trop. Agrie. 310: 185-196.

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