At the time of the survey, yellow crazy ants occurred at high densities over much of
the island’s surface. The main areas free of Anoplolepis were the tern colony and
areas of human habitation (where they were controlled by occasional insecticide use;
Feare 1998). In addition, yellow crazy ants were not observed in a small area to the
south and east of the airstrip (Figure 1), although small numbers of Anoplolepis
were caught in pitfall traps laid in this area. Pitfall trapping was not carried out in the
settlement, tern colony or airstrip, as all were dominated by open grassland habitat
and invertebrate assemblages would have been affected by insecticide use. Three of
the sample plots had very low densities of yellow crazy ants and were defined as
Anoplolepis-free; two of these plots were in the southeast of the island and one in
the central wooded area.