Smerinthus ophthalmica Egg Development Photo Sequence (Outdoors)

A photo sequence for the development of Smerinthus ophthalmica eggs in a natural outdoor environment.

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The female ophthalmica from a recent pairing began laying its eggs, and instead of having lay them all in a container like usual, we decided to let it lay a few on our potted willow outdoors (6/24).

The eggs started bright yellow as normal, but a few days later, we noticed that the eggs were developing in a way we were not familiar with. Normally, we have always only observed the egg development in an indoor environment, and the normal sequence of changes are as follows: bright yellow (initial state), brown mottling forms on edges, brown ring forms along edge, yellow fades to white and brown becomes pale reddish or purplish, entire egg becomes translucent.

What we have begun seeing with the outdoor eggs is somewhat different, however. Instead of a brown mottling on the edges that eventually becomes a ring, the entire egg simply became brownish yellow with no ring, as if someone took a paintbrush and blended the brown on the edges into the yellow (6/27-6/28). As development progressed, instead of the brown becoming a pale red or purple, the entire egg took on a bright red color (6/29-7/1). Later, when the larva inside became fully formed, the egg became translucent just like we have always observed.

It became clear to us, then, that the intermediate stages of development of the egg is different depending on the environment. In fact, wild caught eggs have always been fully bright red, consistent with the bright red ones we observed when developing on our potted willow in a natural outdoor environment. The main differences between outdoor and indoor environments is the temperature (outdoor: mid-high 70s day, 60s night; indoor: constant low-mid 70s), humidity (quite variable, but outdoor generally higher), and sun exposure (- three factors that often influence coloration of larvae as they grow, from our experience. It seems they also influence the egg coloration as well. Why the different colors based on the environment? Perhaps thermoregulation is involved here, but we don't know the details.

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6/27:

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Authors
Alan Liang

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