[Taxacom] Subspecies in insect species

[Kenneth Kinman]

Dear All,
        The thread on John's moths of the genus Aenetus got me wondering (as I have in the past) about subspecies of insects.  I'm sure there are some insect species that are divided into subspecies.  However, my impression has always been that most entomologists just lump potential subspecies into synonymy under the species name.   Why is that?
        For instance, why isn't Aenetus tegulatus divided into subspecies.  Isn't there some difference in the Australian populations that would warrant recognizing them as one or more subspecies separate from a subspecies Aenetus tegulatus tegulatus.  Aren't there discernible morphological differences, and if not, I would think there would at least be some differences in their genomes.
                       -----------------Ken