As the temperatures gradually rise we are seeing the awakening of butterflies. We have been seeing the goatweed leafwings and mourning cloaks occasionally throughout the winter and now they are everywhere. The adults survive the winter by hiding under lose bark, emerging occasionally to collect tree sap. Lately we are seeing a few tiger and zebra swallowtails that have emerged from their cozy winter chrysalis.
|Zebra Swallowtail - Chris Barnhart|
|Early pawpaw flowers|
Checking a number of trees I found a few leaf buds opening and then felt the sudden thrill of discovery. There, on a tiny unfolding leaf, sat a glistening pale green egg of a zebra swallowtail.
A female zebra swallowtail very carefully lays an individual egg on the underside of a leaf. It seems to know that its offspring don't play well together so it lays only one egg per leaf. When the zebra caterpillar emerges, it eats the egg case for energy, and then may eat neighboring eggs if they are available. Since the only likely species on a pawpaw are zebras, it doesn't pay to invest the energy in eggs that will not survive. It is interesting to contemplate how this trait evolved.
Additional thoughts on April 14th:
Tonight as the front has moved through the temperature is forecast to drop to 25 degrees, likely to kill both the pawpaw flowers and the egg we have been following to record its turn to orange in several days. While being the first bud or egg may give the organism a head start, it comes with a price. The zebras are like to continue laying eggs. Whether the pawpaw produces more flower buds is the next question and I am guessing that we won't have pawpaw fruit again this year.