This photo shows a later instar of the caterpillar (that is, it is growing up!). On 6 June I photographed the two in the inset. Today I checked on them and found only one left, but that one has matured into a form more recognizable as a Promethea moth caterpillar. If it survives, it will soon turn into a large green caterpillar, and in time, into a spectacular big moth.