Castalius is a butterfly genus in the family Lycaenidae.

In fact, the delimitation of Castalius versus Tarucus is not yet fully resolved, with some species, such as the dark Pierrot (T. ananda), having been moved between the two genera repeatedly.

But as noted above, it may be that Tarucus and the present genus are eventually regarded as synonymous.

In that case, the older name Castalius would again apply to the two dozen species in question.

[1] Media related to Castalius at Wikimedia Commons