Pyrisitia nise life history
Mimosa Yellow (Pyrisitia nise) Life History

11-14-09, ovipositing

Egg, 11-17-09

Recently emerged caterpillar, 11-19-09





12-31-09, close-up of face

1-1-10, mature caterpillar

Preparing to pupate, 1-02-10

In position to pupate, 1-03-10

Fresh chrysalis, 1-4-10

Nearly ready to emerge, 1-23-10

Fresh Mimosa Yellow, 1-25-2010

One October morning several Little Yellows were visiting the Crucita blooms in my garden, and I was (vainly) trying to get a good photograph of a Little Yellow in flight. I began to track a little yellow butterfly moving around the yard. When I later looked at pictures I realized it was not another Little Yellow but a Mimosa Yellow. It's never wise to assume you know the species of a butterfly without checking carefully! It turned out that this female was ovipositing on shoots of Blackbrush Acacia, Acacia rigidula. The Acacia usually grows as a bush, but the plants this butterfly visited were all coming up in an area of that is regularly mown. The eggs I found were all on the tender leaves of new growth.

I watched a couple of the eggs I found and I collected the caterpillar of this study as soon as it eclosed. Because of the season and weather, I soon was unable to locate fresh Acacia leaves for the caterpillar to eat. I offered Bundleflower (Desmanthus virgatus), because it was more abundant and I had previously raised a Mimosa Yellow on that plant. Sometimes caterpillars resist changes in diet, but in this case the caterpillar accepted the new food.

As I often do, I kept the caterpillar in an unheated room, where it experienced similar temperatures to the outdoors, but was protected from freezing. The weather was cool, and the caterpillar grew very slowly. It took 46 days to pupate. It emerged 21 days later, 67 days after the caterpillar eclosed from the egg.  In comparison, the Mimosa Yellow I raised in warmer weather took only 13 days to pupate and emerged 6 days later, only 19 days after the caterpillar eclosed from the egg. (Both eggs eclosed on the fifth day after being laid.)

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