Caterpillars from separate egg masses laid close together are likely to join to become one big nest (see photo below). This nest was formed from 3 egg masses. It is common to find egg masses/nests on previously infested host trees (you can tell by the caterpillar frass (poo) and shed exoskeleton surrounding/underneath the current nest).
We have also found a few cases of ground nesting caterpillar egg masses laid in the tree fork which is uncommon since they usually lay on the tree trunk (see photos below). This egg mass has successfully developed into a nest above ground!