After a little research, I think phleps is from Greek and refers to blood veins (a phlebotomist is someone who draws blood), and hetero- means different or irregular, so different or irregular veins? Maybe some reference to the venation of the wings. I didn't find anything that referenced this in the one detailed description I found of the genus.
Since I'm thinking about names - the "Three-spotted" part of the common name makes sense, and so does the "tri-" beginning of the species name, and "-guttaria" is close to "gutta" which can refer to spots in latin.
