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)