Browsing by Subject "Ants -- Ecology"
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Item Fire ant dispersal along Texas highways(Texas Tech University, 1998-05) Russell, Scott A.All organisms require specific resources for growth and reproduction. Favorable environments lead to positive population growth and, eventually, to depletion of limited resources. This depletion creates the need for dispersal to relieve crowding and to provide access to new resources. Dispersal can, therefore, be for the purpose of locating necessary resources; e.g., food, mates, shelter, or oviposition sites. Price (1984) described populations as not just increasing or decreasing in numbers, but also moving from place to place and expanding and contracting. Dispersal is adaptive, permitting individuals to escape crowding and colonize new habitats. Organisms must be capable of dispersal to new habitats, and active dispersal requires energy to walk, swim, or fly to a new habitat Passive dispersal does not require energy but does require favorable environmental conditions (wind, water, host). Available habitats require that organisms have access to the habitats, and space or other resources must be available to the immigrant organism. However, the overall geographic range of an organism is seldom one continuum of habitat. Organisms tend to avoid unfavorable habitats; therefore, populations of some organisms may be found in clumps of favorable habitat but may be absent from the vast majority of its habitable range. Haas (1995) found that robins and tlirasbes, for example, traveled along wooded draws connecting planted windbrealcs as if the draws were stepping stones b>etween the windbreaks. The likelihood was greater that birds would disperse between habitats when habitats were connected by a wooded draw.Item Humidity preference and temperature tolerances of four species of fire ants (Hymenoptera: Formicidae: Solenopsis)(Texas Tech University, 1982-08) Potts, Lindsey RandalDistributional data of fire ants in Texas indicated differences in temperature and moisture requirements, A study was begun to more fully understand the effects of these two factors and to determine if laboratory responses would correlate with distributional differences. Four fire ant species found in Texas, Solenopsis aurea, S, geminata, S.invicta, and S. xyloni were used in tests of humidity preference, supercooling temperatures, and temperature tolerances. Attempts to acclimatize the ants failed. Humidity preferences were determined with a linear gradient chamber. The four species showed a marked preference for saturated atmosphere {near 100* RH). Supercooling points were determined with a hypodermic needle microprobe and tel-etherraometer- The mean supercooling points for the ants were -6.7° C for S. aurea, -8.6• C for S. geminata, -8.3• C for S. invicta, and -7.0° C for S. xyloni: Solenopsis aurea and S- xyloni ware not significantly different from each other, and S, invicta and S, geminata were not significantly different from each other; the two groups were significantly different. Three caste sizes were tested in the supercooling experiments. There were no differences between the castes of S. aurea and S. xyloni.- Solenopsis invicta major workers supercooled at a significantly lower temperature than did the medium and minor workers, Solenopsis geminate minor workers supercooled at a significantly lower temperature than did the other castes. Temperature tolerances were determined from one hour exposures. Temperature became a significant cause of mortality at approximately 40» C, and at 450 C all ants perished- Regression analysis showed high variability within replications and significance of the independent effects of temperature, species, humidity, and interactions of these effects. The significance of the independent effects was partly due to the confounding of these effects by the variability within replications. All LD50 values were between 41° C and 44°C.Item The temperature regime in the Solenopsis invicta mound and its effect on behavior(Texas Tech University, 1980-05) Pinson, Carla KayeThe fire ant mound provides a unique environment for its inhabitants. This mound habitat allows for greater changes in temperature than would be available if nests were constructed below the surface. There is a significant difference in temperature regimes in mound soil and undisturbed soil adjacent to the mound. Significant temperature differences exist within the mound on a vertical plane. Surprisingly, a much less significant horizontal mound temperature change was noted. The temperature characteristics have an important impact on ant behavior and data suggest that they migrate in response to mound temperature changes. The S. invicta workers showed the greatest degree of migration, followed by the pupae and larvae. Reproductives and eggs showed less definite patterns of movement.