Effect of termite soldiers on the foraging behavior of Coptotermes formosanus (Isoptera: Rhinotermitidae) in the presence of predatory ants (original) (raw)
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Sociobiology
The specialized defensive traits of tennite soldiers are thought to have evolved largely in response to attacks by ants. Having a greater proportion of soldiers protecting groups of foraging workers could enable termites to expand their foraging areas and enhance their ability to fmd new food sources. This study examined the effect of Pheidole megacephala (F.) (Hymenoptera: Formicidae) on Coptotennes jonnosanus Shiraki foraging behavior, and whether the presence of higher numbers of tennite soldiers enabled foraging workers to better withstand ant attacks and maintain access to food sourses. We also examined how differences in soldier proportions affected the construc tion of new galleries by foraging workers in the absence of ants, and examined whether tennites with higher numbers of soldiers moved into new areas faster than than groups with fewer soldiers. In the fIrst experiment, ants completely occupied the foraging tube and blocked tennite access to their food source after an average ofonly 2d for groups with 5% soldiers compared to an average of 6. 7d for groups with 20% soldiers. However, there was no evidence that tennite groups with 20% soldiers were more likely to explore new areas or construct new foraging galleries faster than groups with only 5% soldiers. Our results indicate that the primary role ofC.jonnosanus soldiers in repelling ant attacks against foraging workers appears to be to guard breaks in the tunnel until workers are able to repair the damage.
The specialized defensive traits of termite soldiers are thought to have evolved largely in response to attacks by ants. Having a greater proportion of soldiers protecting groups of foraging workers could enable termites to expand their foraging areas and enhance their ability to find new food sources. This study examined the effect of Pheidole megacephala (F.) (Hymenoptera: Formicidae) on Coptotermes formosanus Shiraki foraging behavior, and whether the presence of higher numbers of termite soldiers enabled foraging workers to better withstand ant attacks and maintain access to food sources. We also examined how differences in soldier proportions affected the construction of new galleries by foraging workers in the absence of ants, and examined whether termites with higher numbers of soldiers moved into new areas faster than than groups with fewer soldiers. In the first experiment, ants completely occupied the foraging tube and blocked termite access to their food source after an average of only 2d for groups with 5% soldiers compared to an average of 6.7d for groups with 20% soldiers. However, there was no evidence that termite groups with 20% soldiers were more likely to explore new areas or construct new foraging galleries faster than groups with only 5% soldiers. Our results indicate that the primary role of C.formosanus soldiers in repelling ant attacks against foraging workers appears to be to guard breaks in the tunnel until workers are able to repair the damage.
We compared the interaction of Coptotermes formosanus Shiraki with three generalist ant predators, Pheidole megacephala (Fabricius), Ochetellus glaber (Mayr), and Tetramorium simillimum (F. Smith) in a laboratory arena and determined if there were differences in the susceptibility of C. formosanus to attack by these ant species and of the ants to termite defenses. T. simillimum caused significantly greater mortality of termite soldiers in the first experiment and of termite workers in the second experiment. T. simillimum appeared to be more effective at attacking termites in this study because termites did not immediately retreat upon contact with these ants and therefore were more likely to encounter T. simillimum Mortality of P. megacephala was significantly greater than mortality of the other two ant species. P. megacephala appeared to be more aggressive toward termites and more likely to move into vials containing termites. Hence, P. megacephala may have suffered greater mortality because it was more likely to engage in combat with termite soldiers.
We examined the effect of 2 ant species, the bigheaded ant, Pheidole megacephala (F.), and Ochetellus glaber (Mayr), on the Formosan subterranean termite, Coptotermes formosanus Shiraki. We also examined how differences in the proportion of termite soldiers affected the susceptibility of C. formosanus to predation by P. megacephala. In sand-filled containers, C. formosanus was more vulnerable to predation by P. megacephala than by 0. glaber. However, the presence of ants of either species caused substantial mortality of termite soldiers. P. megacephala was much more invasive of termite galleries than 0. glaber. Termites exposed to P. megacephala suffered greater mortality compared with controls, regardless of worker to soldier ratio. However, there was no difference in termite mortality among replicates with different worker to soldier ratios. In the absence of sand, both ant species caused 100% mortality of termites after 1 wk of exposure.
Bioassays were performed to determine the behavioral responses of Coptotermes formosanus Shiraki soldiers to ants or ant extracts. C. formosanus responded differently to semiochemicals of different ant species. A significantly greater proportion of termite soldiers responded aggressively to Pheidole megacephala (F.) than to other ant species. Termite soldiers were significantly less likely to respond aggressively to Monomanum floricola (Jerdon), Tetramorium simillimum (F. Smith), and Ochetellus glaber (Mayr) than to other ant species. Termites avoided contact with 0. glaber in 85.3% of trials, but only avoided contact with other ant species in 18% or less of trials. Termite soldiers were significantly more likely to respond to freshly killed ants than to solvent-treated ants of the same species. Termites also responded similarly to freshly killed ants and dead termites treated with ant extracts, indicating that termite responses were mediated, at least in part, by chemical cues. The ability of C. formosanus to distinguish among different ant species on the basis of semiochemicals could be an adaptive response that allows them to recognize particularly threatening enemies.
Environmental Entomology, 1996
We examined the effect of 2 ant species, the bigheaded ant, Pheidole megacephala (F.), and Ochetellus glaber (Mayr), on the Formosan subterranean termite, Coptotermes formosanus Shiraki. We also examined how differences in the proportion of termite soldiers affected the susceptibilityof C. formosanus to predation by P. megacephala. In sand-filled containers, C. formosanus was more vulnerable to predation by P megacephala than by O. glaber. However,the presence of ants of either species caused substantial mortality of termite soldiers. P megacephala was much more invasiveof termite galleries than O. glaber. Termites exposed to P megacephala suffered greater mortality compared with controls, regardless of worker to soldier ratio. However,there was no difference in termite mortalityamong replicates with different worker to soldier ratios. In the absence of sand, both ant species caused 100% mortality of termites after 1wk of exposure. KEY WORDS ants, Coptotermes formosanus, predation SUBTERRANEANTERMITES ARE major pests of wood products. Efforts to control the Formosan subterranean termite, Coptotermes formosanus Shiraki, in the Hawaiian islands cost at least $60 million each year (Yates and Tamashiro 1990). A mature C. formosanus colony contains 2-4 million termites on average (Su and Scheffrahn 1988). The main and satellite nests of C. formosanus can occur anywhere within a foraging area of >200 m in diameter (Su and Tamashiro 1987). C. formosanus is also capable of establishing aerial colonies with no connection to the ground. Because of these characteristics, C. formosanus is vel)' difficult to control. Prevention of termite infestations of buildings in Hawaii has relied primarily on the use of insecticide applications to the soil (Tamashiro et al. 1990, Grace et aI. 1993a). However, the longevity of most