One of the significant potential problems of rearing butterflies in the lab is sickness. Both viruses and bacteria can infect and kill butterfly larvae and pupae. Some basic steps to avoid sickness include a regular regimen of the following:

1. Replace host plant
2. Remove caterpillar frass
3. Disinfect rearing containers

How frequently you need to perform these housekeeping functions depends upon these criteria:

1. Butterfly taxon
2. Host plants used
3. Caterpillar setups
4. Caterpillar Numbers

Depending upon your experience with rearing caterpillars, I would always take a serious look at the number of caterpillars you are raising.  Mass rearing of butterfly caterpillars doesn't normally pose any threat to the resource involved or to the environment because of the reproductive capabilities of butterflies--especially if you obtain hundreds of eggs out of a single female butterfly.    However, with some species of butterflies, the more you rear, the higher the odds of sickness.  Always take that under consideration when someone offers you 50+ eggs of Papilio indra.