Itioka Takao, Inoue Tamiji
Laboratory of Entomology, Faculty of Agriculture, Kyoto University, 606-01, Kyoto, Japan.
Center for Ecological Research, Kyoto University, Shimosakamoto, 520-01, Otsu, Japan.
Oecologia. 1996 Jun;106(4):448-454. doi: 10.1007/BF00329700.
The intensity of attendance by a honeydew-foraging ant, Lasuis niger, on the red wax scale insect, Ceroplastes rubens, was estimated at different manipulated densities in the field. The time that individual ants were present and the total attendance time (seconds x number of ants) of ants on scale-infested twigs significantly increased as the density of C. rubens increased, i.e. ant attendance was density dependent. To determine the effects of density dependence of ant attendance on parasitism of C. rubens by Anicetus beneficus, we measured parasitism rates in the field at different density levels of C. rubens both with ant attendance and with ants excluded. Parasitism rates were higher when ants were excluded, at each density level. Although the parasitism rate significantly deceased as scale density increased, whether or not ants attended, the difference in parasitism rate between density levels was strikingly less without ant attendance. Therefore, the density-dependent decrease of parasitism rate was more pronounced with ant attendance. Mortality not due to parasitism showed density dependence in both conditions and did not change when ants were excluded. These results indicate that attending ants reduce parasitism and that, as a consequence of the density dependence of ant attendance, the efficiency of reduction of parasitism by ants is enhanced at higher densities of C. rubens.
在野外，通过对不同操纵密度下黑毛蚁（Lasuis niger）对红蜡蚧（Ceroplastes rubens）觅食的强度进行了估计。随着红蜡蚧密度的增加，单个蚂蚁出现的时间以及蚂蚁在有蚧虫寄生的嫩枝上的总出勤时间（秒×蚂蚁数量）显著增加，即蚂蚁出勤具有密度依赖性。为了确定蚂蚁出勤的密度依赖性对红蜡蚧被益蚧蚜小蜂（Anicetus beneficus）寄生的影响，我们在野外测量了不同红蜡蚧密度水平下，有蚂蚁出勤和排除蚂蚁两种情况下的寄生率。在每个密度水平下，排除蚂蚁时的寄生率更高。尽管无论有无蚂蚁出勤，寄生率都随着蚧虫密度的增加而显著下降，但在没有蚂蚁出勤的情况下，密度水平之间的寄生率差异明显更小。因此，在有蚂蚁出勤的情况下，寄生率的密度依赖性下降更为明显。在两种情况下，非寄生性死亡率都表现出密度依赖性，并且在排除蚂蚁时没有变化。这些结果表明，出勤的蚂蚁会降低寄生率，并且由于蚂蚁出勤的密度依赖性，在红蜡蚧密度较高时，蚂蚁降低寄生率的效率会提高。
