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Camponotus foreli (Emery) and Cataglyphis iberica (Emery) are two sympatric, subordinate ant species that have been found to fight in attacks that usually conclude with the death of many workers of both species and with nest abandonment by C. iberica. These harassment episodes have been observed in two different areas and over many years of study. No such attacks of C. foreli were observed in the study areas against any other ant species, nor did any other ants attack C. iberica nests, and laboratory confrontations confirmed this specificity. These attacks neither eliminated C. iberica colonies, nor distanced them from C. foreli nests. Moreover, there was no real competition for food between the species: in an experiment where all C. iberica colonies were eliminated from an area, rates of prey and liquid food collection by C. foreli nests in the exclusion zone were similar to those found in the control zone with C. iberica, and the activity rhythms of C. foreli did not change in the absence of C. iberica. The hypothesis of competition for a nest site is more consistent. Both in the laboratory and the field, the most frequent outcome of these aggressive interactions was the occupation of the C. iberica nest by C. foreli. This behavior may be advantageous for C. foreli, because it is much less skilful at excavating than C. iberica. One of the chief concerns of this study is to show that such interference interactions, typical especially of dominant, very aggressive species, are also found between subordinate, apparently nonaggressive species.

The relationships between flowering plants and their insect visitors were studied in a Mediterranean grassland in north-east Spain. Floral traits (size, shape, symmetry, and colour), floral rewards (pollen and nectar), flowering period, and floral visitors were recorded for the 17 most abundant plants in the community. Flowering was year-round, but most species flowered in spring. The three species that flowered after spring had small flowers, but the distribution of floral features (including rewards offered) did not show a strong seasonality. Ants contributed 58.5% to the flower visits recorded. Other frequent visitors were beetles (12%), flies (9.5%), honey bees (6.4%), wild bees (6.4%), and wasps (5.2%). Honey bees were most abundant in April, wild bees from April to July, beetles from May to July, and ants from May to September. The lack of tight plant-insect associations was the rule, with most plant species visited by a rather diverse array of insects representing two or more orders. The plant species having narrower spectra of visitors either had flower rewards exposed or attracted mostly illegitimate visitors. By means of correspondence analysis four categories of plants were defined according to their main groups of visitors: (1) honey bees and large wild bees; (2) large wild bees; (3) ants and beetles; and (4) beetles and small-sized bees. The Mantel test was used to calculate correlations among four matrices representing similarities in visitors attracted, floral morphological traits, pollen-nectar rewards, and blooming time, respectively. In spite of seasonality shown by the different insect groups, results indicate that the observed patterns of visitor distribution among plants were most affected by pollen-nectar rewards.