As nouns,
vespertilian bat is a hypernym of
Pipistrellus hesperus; that is, vespertilian bat is a
word with a broader meaning than Pipistrellus hesperus:
Pipistrellus hesperus: a vespertilian bat of western North America
vespertilian bat: a variety of carnivorous bat
Other hypernyms of Pipistrellus hesperus include
vespertilionid.