ABSTRACT.1. The distribution ofDactylopius opuntiae(Cockerell) colonies onOpuntia ficus‐indica(L.) Miller cladodes collected during a prolonged drought, was recorded for the proximal and distal portions of the cladodes, for the exposed and sheltered surfaces, the edges, and in relation to the proximity of the colonies to areoles at the base of the thorns.2. Most of the colonies were found on the more sheltered parts of the cladodes and a disproportionately large number of the colonies on exposed surfaces had settled below the areoles.3. Individuals in colonies on the exposed surfaces were all protected by a relatively hard, compacted wax cover and were thus less vulnerable to simulated rainfall than those on sheltered surfaces. Thorns provided some protection from simulated rainfall for individuals in colonies on exposed surfaces, but not for individuals on sheltered surfaces.4. Natural rainfall greatly reduced the numbers of colonies, but did not significantly change the distribution of the colonies on the cactus cladodes.5. Rainfall does not explain the observed distribution ofD. opuntiaecolonies on the cladodes, but does explain the poor performance of cochineal insects as biological control agents of prickly pear cacti in high rainfall area