The Taylor’s Checkerspot larvae have nearly all entered their warm stage of diapause. From this year’s eggs laid, over 490 larvae hatched at the Greater Vancouver Zoo in Aldergrove, BC. This is the first year to have the Taylor’s Checkerspot Butterfly breeding program at the Greater Vancouver Zoo. The larvae will be kept over winter at the zoo and some will be kept to continue the captive breeding population, while the rest will be released back at Denman Island prior to pupation and butterfly eclosure.
The first larvae to hatch are now in Instar V and have fully entered ‘warm diapause’. The shedding of the exoskeleton is the method in which larvae grow. They create new skins in stages known as instar and because this process is so energetically demanding it is a process where only healthy larvae will survive. Taylor’s Checkerspot larvae experience five different stages of instar prior to entering diapause and over wintering. Food consumption and activity levels will vary amongst the pre-diapause larvae depending on their current stages. When diapause is beginning larvae will begin to slow down activity and reduce the amount of consumption, they will start to cluster and web up together in a group hiding under rocks or logs in the wild, or in between layers of paper towel for our captive group!
Diapause is a stage of dormancy when development is delayed. Animals enter this stage during periods of changed environmental conditions, such as temperature extremes or reduced food availability. For the TCB larvae there are two separate stages of diapause one during the summer known as ‘warm diapause’ and a dormancy that takes place over the course of winter, or ‘cold diapause’. Once the caterpillars have completed the shedding of their exoskeleton and stopped eating they will begin to web up and enter the dormant state until temperatures begin to drop again. The primary reason for this behavior is to protect themselves from running out of food and by being less susceptible to temperature extremes. Right now the primary food source is getting more scarce to be found, as most vegetation is dried out and weathered.
Caterpillars webbed up in ‘warm’ diapause
During this time period we are checking the caterpillars daily and ensuring that humidity is remaining high. Once the caterpillars are fully dormant and no frass is created and no food eaten we will stop placing food supply in the cups until they begin to become active again.
Taylor’s Checkerspot Butterflies are actually unique to other butterflies due to their ability to enter these stages of diapause multiple times throughout the year.