Temporal Variability in Weaver Ant Oecophylla longinoda Latreille (Hymenoptera: Formicidae) Nest Characteristics in Selected Host Plants

Weaver ants (Oecophylla smaragdina and O. longinoda) are famous for their impressive nest constructions where they weave together living leaves on their host plants. Also, they are known to protect tropical tree crops against insect pests and are thus being utilized for biological control. To optimize their use, nest numbers have been used to track weaver ant abundances in plantation, assuming the number of nests reflects ant numbers. In this study we compared nest size, the density of ants and the proportion of workers in nests between three host plants (cashew, citrus and mango) and between two seasons (rainy and dry). Nest size, ant density and worker proportion all differed between host species, whereas only nest size and worker proportion showed seasonal differences and only on mango and citrus, respectively. On hosts with smaller nests (in increasing size order: cashew, citrus mango), ant densities in the nests were higher, and the proportion of workers in the nests seemed to increase during seasons where food production on host trees decreased, or on hosts where more trophobionts were cultured inside nests. These results have implications for the development of methods used to estimate ant numbers and they raise interesting questions about the function of weaver ant nests.