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RHINOSTOMUS BARBIROSTRIS
Bottlebrush Weevils

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Classification

Phylum Arthropoda

Class Insecta

Order Coleoptera

Family Curculionidae

Subfamily Dryophthorinae

Genus Rhinostomus

Species R. Barbirostris

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RHINOSTOMUS BARBIROSTRIS
Bearded Weevil

Rhinostomus barbirostris, common name Bottlebrush Weevil or Bearded Weevil, is a species of true weevil family.

Rhinostomus barbirostris can reach a length of 11-40 millimetres, excluding beak. It is probably the third largest weevil in the world. The basic color is black. The pronotum is as long as wide and densely punctate. The elytra bear distinct striae and are deeply punctate. Males have characteristic long reddish gold hairs on the apical portion of the long, straight, and dorsally dentate rostrum. The antennae are long and slender, and strongly elbowed. The front tibiae have two or more large, sharp teeth on the inner face. This species shows an unusual sexual polymorphism, as some males in each population are smaller than other males and resemble females.

This common and widespread species occurs mainly in Central America and South America, while similar species in the genus occur in the United States, Africa, Madagascar, Borneo, and India.

The bearded weevil, attacks coconut trees, oil palms and other species of Arecaceae. Besides direct damage, R. barbirostris may be a vector of diseases in coconut and oil palms, such as stem bleeding & red ring disease. Currently, the only method to control this weevil is by visual observation of damage and removal of infected plants.

Several striking secondary sexual characters of the weevil Rhinostomus barbirostris serve as weapons in intraspecific battles between males for females about to oviposit. Smaller males adopt two alternative behavioral tactics in these battles which seem designed to minimize the loss in reproduction which would otherwise result from their inferior fighting abilities. Although the beetles may thus be polymorphic for fighting behavior, there was no sign of morphological dimorphisms.

The sizes of their weapons (long rostra) were linearly rather than geometrically related to the sizes of other body parts. The males behavior suggests that there is strong sperm precendence in this species.


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