In most individual adult butterflies, diapause begins with its southern migration, but unlike other insects in this state, it remains active.[19][2][5][24][25][26] When diapause is initiated the butterflies accumulate and store lipids, proteins and carbohydrates.[21] Monarchs migrating to Mexico accumulate more lipids than those migrating to California.[27] Fats and lipids reduce water to provide energy reserves and prevent desiccation.[28] These substances are used to maintain the insect throughout diapause and to provide fuel for development following diapause termination.