You have passion vine growing and notice eggs on the vine. You live in an area where you will see both Gulf Fritillary and Zebra Longwing butterflies flying about. Which one laid the eggs?
First, as a general rule, Gulf Fritillary butterflies prefer to lay eggs in bright sunlight, on plants growing in full sun. Zebra Longwing butterflies prefer to lay eggs in the shade, on plants growing in the shade. That being said, Zebra Longwing butterflies will lay eggs on plants growing in the sun on cloudy days.
Second, both lay eggs singly, one at a time. Why do we see eggs in clusters at times? Simple!
Zebra Longwing butterflies lay eggs in the tip of new growth, one at a time. They are often in clusters because there are usually only a few ‘perfect spots’ that their instinct allows them to use. They also lay eggs on tendrils near the tip of the plant. It is fairly unusual to see their eggs on leaves unless those leaves are right at the tip of a vine.
Gulf Fritillary butterflies are not so particular. They will lay eggs almost anywhere on or near the plant. They usually don’t lay on the freshest growth.
When they lay eggs off a plant, it wasn’t an accident. They lay eggs off the plant as often as on the plant. A blade of grass, a strand of Spanish moss, a post, even you are fair game if you are near the plant.
Of course, there are always exceptions. Be prepared for those that do not play by the rules.
Side note: freshly laid eggs of both species are yellow. As the caterpillar inside develops, the eggs turn a dark burnt orange color.
Zebra Longwing caterpillars are dark when they first hatch, not totally white as they are once they begin to grow.
Look closely at the image below. Do you see the clear egg shells? A predator, such as a tiny spider or a lacewing larva has drained the egg of its contents.