Monarch caterpillars go through five instars (the period between molts). He stopped eating early today and lives attached to the underside of the leaf – this is the second time I have observed this behavior and indicates the beginning of the molt. Murray is molting now (no photos since I do not want to disrupt the event – he is most vulnerable during the molt).
I think Murray is entering his fourth instar based on his size and time since he “hatched” from his egg. There are supposed to be distinct white spots on his forelegs during the fourth instar and one of the photos from yesterday shows a small white spot probably indicating the third instar (click on the photo to see a large version – the white spot is visible on the first leg from his head). Also, Murray showed the typical third instar eating behavior – a cutting motion on the leaf edge which you can clearly see in yesterday’s close-up. But what do I know; this is my first monarch midwifery.
During the fourth instar, those white spots should be conspicuous. When he starts eating again, he should be even more hungry – I will measure him then and compare with the “official” stats.