>>Actually, crossing two subspecies will produce an intergrade, not a hybrid....

Intergradation concerns populations and intergrades are individuals that actually attest to the phenomenon. What you get when you cross subspecies in captivity, completely separated from the context of intergradation as a natural phenomenon, is hybrids, both in the general sense and the formal. It would be an intraspecific hybrid.
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2.2 Thamnophis elegans vagrans
0.1 Thamnophis sirtalis tetrataenia
1.1 Natrix maura