Spring Azure & Summer Azure
Spring and Summer Azure butterflies look very similar. Spring Azures have only one brood with a limited flight period (usually April and early May in our area). By contrast, Summer Azures have multiple broods throughout the year, from late March through early October. In our area, it is safe to call any Azure seen in June and later a "Summer Azure". But the situation is much more complicated in spring, because "Summer Azures" also have an early spring brood.
This is a Spring Azure, photographed April 21, 2019 at Twin Creek MetroPark. Notice how the markings are brownish rather than black, and the wings look "dirty". These are indications that this is a true Spring Azure. The habitat is also important. Dogwood is one of the main host plants for Spring Azures, and I found this butterfly at (appropriately) Dogwood Pond.
This is a female Spring Azure. Females have a wider black border on their forewings than the males.
Summer Azure butterfly resting on a Queen Anne's Lace flower.
This is a Summer Azure, photographed July 14, 2017, at Cox Arboretum. Summer Azures are more common and widespread than Spring Azures.
This is a male Spring Azure, basking on a wooded trail with his wings open.
Squills (genus Scilla) are a favorite nectar source for Spring Azures. Squills are non-native flowering bulbs that bloom in early spring. These bulbs have escaped from cultivation and are growing wild in some locations, such as Sugarcreek MetroPark, where this photo was taken.
Summer Azures rarely rest with their wings spread. The only reason we can see the blue upper surface of the wings here is because (sadly) this butterfly has been nabbed by a crab spider.
For contrast, here is an early spring brood Summer Azure, photographed at Grant Park in Centerville on April 3, 2019. Notice how the wings look "cleaner" (whiter) and the markings are black rather than brown. These are strong indications that this is a Summer Azure rather than a Spring Azure, despite the early date.
Here is a date guide for our area:
Early brood Summer Azure - late March through mid-April.
Spring Azure - one brood in April and early May.
Summer Azure - several subsequent broods from mid-May through early October.