Pollen feeding and survival of the boll weevil (Coleoptera: Curculionidae) on selected plant species in northeastern Mexico

Alternate feeding hosts of adult boll weevils, Anthonomus grandis Boheman, were studied in Tamaulipas, Mexico, by (1) isolating and identifying pollen grains from the alimentary tract of weevils caught in pheromone traps in Tamaulipas, Mexico, during 1985, 1986, and 1987: and (2) evaluating the potential importance of alternate host plants in the biology of the boll weevil by recording the survival rates, fat body accumulation and reproductive development of boll weevil adults when fed flowers and buds of selected plant species. In total, 3,348 pollen grains of all kinds were isolated from 1,204 boll weevils captured in pheromone traps in central Tamaulipas. Of 406 individual weevils collected from October through May, 34.7% were found with some type of ingested pollen grains. Boll weevils with ingested pollen were found in every habitat in which traps were placed, although the percentage of weevils with ingested pollen varied between habitats and with distance from cultivated cotton. The mean number of pollen grains of all species per weevil was 12.9 +/- 3.8 (mean +/- SE) (n = 406), and several weevils were found with > 200 ingested pollen grains. The ingested pollen grains were from fourteen identified plant families. The most commonly represented families were Compositae (29.9%), Leguminosae (14.6%), Malvaceae (5.3%), Gramineae (0.6%), and Fagaceae (0.6%). Adult boll weevils readily fed on the various noncotton plants (Compositae, Malvaceae, and Cactaceae) offered in field cages. Mean survival times of boll weevils were significantly greater when fed either pure pollen mixtures, Gossypium hirsutum L. buds (cotton), Opuntia lindheimeri Engelm. (Cactaceae) flowers, or Abutilon hypolecum Gray (Malvaceae) than controls (water only). Fat body development of boll weevils fed these food sources was also significantly greater than controls. Polyphagous pollen feeding behavior may be an important survival strategy of the boll weevil in the absence of reproductive hosts, especially in tropical habitats where adult boll weevils may be active throughout the year.