Unidentified > Insects > Guava galls, New Caledonia

It was said to be a gall induced by an insect, and the mostly like cause was aphids/Hymenoptera/psyllids. The photo shows a very well developed gall, and so the insects may have departed. Look at the younger galls to get a better chance of finding the insect. A physiological condition and Eriophyid mites were also suggested, but thought less likely to be the cause.