Observed a new behaviour today. One of the large Monarch caterpillars (probably 4th or 5th instar) was really pi**ed off and spitting green fluid for all he was worth! Internet research gave 3 possible causes:
1. Poisoning. Don't think it is as other 25 or so on plant all ok.
2. Disturbance. Possibly.
3. Overcrowding. Probably. At least 25 caterpillars have been through their instars on this plant over the last fortnight, food is rapidly diminishing. The caterpillars have eaten the ends of the stalks and the seed pods as well as most of the leaves. I think there are just enough edible bits for them to finish growing and go off to do their next bit. I've moved the new crop of tiny caterpillars to a reserve plant that I keep under a net.
little and large
