Browsing by Subject "Solenopsis invicta -- Control"
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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 Pheromonal control over worker execution of sexual larvae in fire ants (Solenopsis invicta)(Texas Tech University, 2001-05) Klobuchar, Emily AnnI studied the phenomenon of worker execution of sexual larvae in the red imported fire ant, Solenopsis invicta. Both fertilized and unfertilized queens as well as queen corpses were equally effective in inducing executions by 96 h. Colonies receiving acetone (control) or queen extracts in acetone did not differ in execution rates. In sharp contrast, however, colonies receiving an extract of queens in a buffered solution killed significantly more sexual larvae than those colonies receiving only the solution (control). The extract was as effective as live queens, and, as in all tests, were introduced once every 12 h at concentrations of single-queen equivalents. In addition to having full activity, the extract was stable, as the percentage of larvae killed did not differ between jfresh (Id) and old (21 d) extracts maintained in clear vials at room temperature. The poison sac was identified as the likely storage site of the pheromone. This sac also houses the venom alkaloids and queen retinue pheromone, but these chemicals are readily extracted with strong organic solvents, unlike the 'execution' pheromone. There was no correlation between ratios of the two most abundant alkaloids and queen age, but ratios of saturated to unsaturated alkaloids were significantly greater in wingless queens than in winged queens. The queen venoms are less derived than those of workers perhaps because the execution pheromone has constrained their evolution.Item The effect of acute exposure to relative humidity and temperature on the worker caste of four species of fire ants(Texas Tech University, 1982-05) Braulick, Lori SNot available