Bearded Weevil

Curculionidae, Rhynchophorinae, Sipalini, Rhinostomus ( = Rhina) barbirostris. Portuguese: Broca do tronco do coqueiro (Brazil, larva).

Uniquely, this weevil's snout possesses a dense vestiture of erect, reddish-brown hairs, somewhat resembling a bottle brush. Males use this pubescent proboscis apparently to gain sexual favors from females, whom they stroke assiduously with it.

This black species is fairly large (BL 3.5— 5 cm), with a cylindrical body, ridged wing covers, and extra long forelegs, the tibiae of which are heavily spined on the underside (fig. 9.16d). It is usually encountered walking on tree trunks, which males patrol in search of females that are in the act of oviposition. Females drill holes in the bark of newly fallen palm trees, place eggs in these, and then seal them with a gluelike secretion. If multiple males find a female thus engaged, they will spar with their beaks, trying to dislodge each other. The winner of these battles mates with the female (Eberhard 1980).

The species is widespread and moderately common in moist forests throughout Central and South America. Its larval hosts are various palms, including the coconut, which it often damages severely by ovipositing in the stipes that the developing larvae later destroy. Larvae also mine the trunks of mature trees (Bondar 1922).

The larva is moderately large (BL 20— 50 mm), cylindrical (not tapered like that of the palm weevil), and curved strongly just behind the thorax. Its head is yellow, and on the back of the first thoracic segment is a large yellowish plate with small incisions on its rear margin. The terminal segments are greatly restricted and retractable within the rest of the body.

References

Bondar, G. 1922. Broca do tronco do coqueiro.

In G. Bondar, Insectos nocivos e molestias do coqueiro (Cocos nucifer) no Brasil. Imp. Off. Est. Bahia, Bahia. Pp. 18-31. Eberhard, W. G. 1980. Horned beetles. Sci Amer. 242(3): 166-182.

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