Soft scale insects closely associated with ants have been included in the subfamily Myzolecaniinae. This group has a worldwide distribution and contains the most derived insects in the Coccidae. Morphological features have evolved in such a way that these scale insects can no longer survive without attendance by their ant symbionts. These scale insects are well represented in the New World where the following genera occur: Akermes, Aztecalecanium, Cryptostigma, Cyclolecanium, Megasaissetia, Neolecanium, Octolecanium, Pseudophilippia and Toumeyella. The Myzolecaniinae are thought to be composed of several non-related genera which share common characters such as: the reduction in size of legs, antennae and anal tube; the increase in size of spiracles; lack of eyespots; and other shared characters that could be a result of parallel evolution in the adult female morphology. Several scale insects treated in the present study are known to cause losses to agriculture. For example, Cryptostigma silveirai is a serious pest of grape vines in Brazil, and Toumeyella erythrinae is a pest of erythrina trees in Mexico. In the USA, T. parvicornis often causes serious damage to pine trees. The present study presents our understanding of New World ant- and bee-coccid relationships, their ecology and biogeography.