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Mating pair
© Paul Labus | After mating the female Karner blue lays eggs directly on lupine plants. The eggs are about one millimeter in diameter. A freshly-hatched caterpillar is equally as small. During a period of 10 to 14 days after hatching, while feeding exclusively on lupine leaves, a caterpillar grows to about 20 millimeters in length.
The next stage in development is pupation. The process begins with the caterpillar shedding its outer shell and attaching itself to an appropriate substrate. Over the following seven to 10 days it will complete the metamorphosis into an adult butterfly. During that time, the development of external features such as wings, antennae, legs and eyes clearly is visible.
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Progression from caterpillar to pupa
© Paul Labus | The process culminates with the emergence of an adult butterfly. The outer protective shell splits near the head and the butterfly uses it legs to crawl out. The wings begin to expand immediately as the butterfly searches for a protective spot. It hangs motionless for about 45 minutes as its wings dry.
Karner blues most commonly are seen fluttering low to the ground in large sunny open areas searching for mates and feeding on nectar from a variety of wildflowers. After mating, females spend most of their time moving among lupine patches were they lay their eggs. On average, the adult lives for about a week in the wild.
There are two broods of Karner blues per year, one in late spring and another in mid summer.
- In early May, caterpillars begin hatching from eggs that were laid the proceeding summer. Adult butterflies usually emerge at the end of May into the first week of June.
- Eggs from the first brood begin hatching in mid June. The peak adult second brood flight is mid July. During the second brood females once again lay eggs directly on the lupine. As the plants die back for the year the eggs remain on the dead vegetation where they over-winter.
The following spring the cycle will begin once again.
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