Ants in tropical irrigated rice : distribution and abundance, especially of Solenopsis geminata (Hymenoptera: Formicidae)
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At least 62 species of ants were caught at baits in Philippine rice fields, notably in the bunds (levees) of irrigated rice. Many were relatively uncommon or localized. Apart from the ubiquitous Tapinoma sp. nr indicum Forel the most widespread was the aggressive Solenopsis geminata (Fabricius) which was often very abundant in fields with bunds that were disturbed by regular repair. This ant was scarce or absent in relatively undisturbed well-vegetated bunds where Pheidole spp. were sometimes common and where up to 14 different species were recorded in bunds of a single field. Colonies were spaced out along the bunds where foraging territories sometimes overlapped, except for those of the competing dominants S. geminata and Pheidole spp. In general, S. geminata retained its overall foraging areas from year to year but those of non-dominant ant species could vary considerably. Bunds of low-lying fields that are deeply flooded in the wet season were recolonized by S. geminata in the wet season. This ant occurred as separate colonies with workers from nests that differed in degree of mutual aggression. Such aggression was not observed in foraging areas. Solenopsis geminata and other species foraged into, and nested within, dry fallowed fields after the crop was harvested. In the crop season, they foraged across mud during periods of up to one week when farmers allow irrigated rice fields to drain before flooding. Solenopsis geminata workers also foraged across the closed crop canopy. At such times they were commonly observed preying on hemipteran and lepidopteran pests and on eggs and young golden snails (Pomacea canaliculata Lamarck) which are serious rice pests in the Philippines.
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