Arctiidae, Arctiinae Length (Last Instar) : 40mm.

After 4 weeks, the growing larvae had reached their final instar, and was approaching pupation when individuals began acting rather strange. Although looking healthy, they would suddenly stop feeding and stayed hunched in one place, slowly shrinking in length, before finally dieing. There was no obvious reason for their plight, and what-ever happened eradicated the whole culture within two weeks. The only possibility, was that the foodplant collected from wild ground by the road-side nearby had been contaminated by a farmer spraying weed-killer or insecticide in the adjacent fields.

I have had a similar instance on a new culture of a large species of Phasmid collected in Fiji many years ago which suffered the same fate, with almost the same situation of reaching final instar and then suddenly all dieing. The problem of living in an agricultural environment. :(