Aspects of ecology of weaver ants (Oecophylla longinoda Latreille) (hymenoptera: Formicidae) in Tanzania

PhD Thesis

Studies were undertaken between 2012 and 2015 in Mtwara region, Tanzania to establish an understanding of the factors affecting population dynamics in Oecophylla longinoda. Experiments included assessment on; how viable offsprings are produced, when nuptial flights occur and environmental cues that trigger flights. Oecophylla longinoda queens were collected at four steps: before flight, immediately after leaving the nest, up to 12 h after leaving the nest and after settling naturally following the nuptial flights. Only eggs produced by queens (n=65) collected after settling naturally hatched into larvae. None of the 527 winged queens that were collected before flights and immediately after leaving the nests produced viable eggs. Observations on 56 flights recorded from 25 colonies revealed that, flights took place in the evenings. Days with flights were associated with higher relative humidity (p=0.018), less sun shine (p=0.045) and lower wind speed (p=0.034) when compared to days without flights. This knowledge offers a tool to improve forecasts of O. longinoda flights, facilitating collection of mated queens to stock ant nurseries that would supply ant colonies for IPM-programs. Furthermore, feeds that can be used as food supplements to the ants during food scarcity namely anchovy, earthworm, fish intestines and chicken intestines were tested on 20 colonies. O. longinoda preferred anchovy to the rest of the provided feeds. More ants’ activity was observed on fresh-ground anchovy compared to the dry form. Large sized particles were easily removed than smaller particles. Analytical Hierarchy Process showed that, earthworm and fish intestines were the most available feeds. Thus, during reduced food availability, farmers in the study area can use such materials as feed supplement for O. longinoda colonies. Fresh or dry anchovy of large particle sizes can be used wherever available. On factors affecting temporal abundance of weaver ants, the percentage of shoots with weaver ants was significantly (p=0.0003) associated with cashew growth phases. More weaver ants were recorded during cashew vegetative and reproductive phases than dormancy. Rainfall and temperature negatively affected number of nests, while relative humidity was negatively related to the number of shoots with weaver ants. Thus, weaver ant augmentations strategies should consider the phenology of cashew crop and weather parameters.

Danish International Development Agency (DANIDA)