Lampropeltine Colubrids have defined and identifiable sex chromosomes. They use the ZW system like birds, rather than the XY system we mammals use. As such, their sex determination is genetic (frequently called GSD) rather than temperature-dependant like that seen is some geckos and some Chelonians. Hope that helps.

Also, watch that 87F incubation temp. Your eggs are likely to develop very quickly and you may end up with tiny hatchlings as a result. Lower temperature generally equates to more robust hatchlings (within reason).
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-Cole