Using a 60 Watt Bulb

Rearing cages, terrariums, and containers do not necessarily need this intense a light source to keep immatures from hibernating.  This technique is especially appropriate for the genus, Limenitis, which includes viceroys (Limenitis archippus), red spotted purples (Limenitis astyanax), white admirals (Limenitis arthemis), weidemeyer's admirals (Limenitis weidemeyeri), and lorquin's admirals (Limenitis lorquini).

This technique of exposing caterpillars to 24 hours of light is especially helpful on recently molted second instar viceroys, purples and admirals.  These freshly molted second instars immediately measure daylength or photoperiod and either construct rolled-leaf hibernacula at third instar or they feed past third instar, through fourth and fifth instar, pupate, and emerge adult butterflies.  

The hibernate decision is measured at second instar and is executed at third instar.  The threshold daylength of whether a third instar constructs a rolled-leaf hibernaculum and bypasses hibernation is a function of taxon and latitude.  The further south the population of viceroy, red-spotted purple, white admiral, weidemeyer's admiral, or lorquin's admiral, the lower the daylength threshold exists where third instar caterpillars will bypass hibernation and create another generation.  Conversely, the further north the population of Limenits, the higher the daylength threshold for the caterpillar to avoid diapause.

To keep things simple for newer breeders of Limenitis, it is advisable simply to expose freshly molted second instar caterpillars to 24 hours of normal room light until the caterpillar molts to fourth instar where it will be committed to proceed through to adult within 4-6 weeks of having been laid as an egg.

Light on Speyeria Species

When rearing Speyeria species, one technique to break unfed first instars out of diapause is to place them on the leaves of fresh violets or pansies.  When the larvae move around to find a place to hide to diapause, keep moving them over and over while exposing them to high humidity and 24 hours of light a day.  Usually, within 96 to 144 hours, they will start feeding.