Citrus Swallowtail eggs should be kept in a closed plastic container to prevent drying out. They begin as a yellow or cream colour, gradually darkening to almost black as the caterpillar develops inside. When the egg turns black, hatching typically occurs within a day or two.

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Important egg-care tips

• Keep eggs in a closed and humid plastic container, but never leave them wet.
  
• Do not add leaves before hatching — fresh leaves release moisture and can cause mould, which easily kills Swallowtail eggs.
  
• Once caterpillars hatch, move them to a new container with fresh host plant leaves and keep the environment lightly ventilated to avoid condensation buildup as this can drown larvae.
  

When the larvae are in L2 or 3 and feeding well, you can transfer them to a mesh cage or a larger plastic container. Swallowtails also thrive on living host plants if you have potted citrus or choisya - even better in a greenhouse - which can greatly improve growth and reduce daily maintenance.