Post Hibernation Strategies
The key to successfully implementing post hibernation strategies is to keep butterfly immatures alive from predation, dessication, and mold during the winter as was discussed in our Overwintering Techniques section.
Like other rearing philosophies, post hibernation strategies naturally align themselves with three of the four stages of the life cycle of a butterfly--egg, caterpillar, and chrysalis. I am also including a separate section on admirals and viceorys--since post-hibernation strategies for that group is somewhat niche.
Since the point of post hibernation strategies is get eggs, caterpillars, and pupae to break diapause or hibernation, some of the strategies and techniques to accomplish this include the following:
Eggs (1)Butterfly eggs should not be brought out of their cold weather hibernation cycle until fresh food plant is naturally available. Once you do bring them out of the cold, expose ova to long day photoperiod and intermittant humidity (spritzing or mist spraying with water).
Please see the hatching eggs section for more information on handling butterfly ova.
Butterfly caterpillars that overwinter generally at all stages including:
- Unfed first instar caterpillars
- Half-grown caterpillars (third or fourth instar caterpillars)
- Mature Last Instar Caterpillars (Caterpillars that will pupate in the spring)
Pupae (3)Butterflies that overwinter as pupae can be brought out of the cold roughly 90-150 days after the initiation of the cold weather treatment--depending upon the species and habitat. For butterfly species that have pupae that diapause, they do NOT necessarily need a long summer and then a long winter before emerging. These butterflies tend to not monitor time during the summer. In other words, if someone wanted to shorten the time period between pupation and emerged adults, they could easily expose diapausing pupae to 1 month of summer, and then place the pupae in the refrigerator for approximately 4 months; and then bring them out for emergence.
Another consideration is if you are overwintering pupae with the intent of releasing butterflies back into the wild at the right time, I would first identify when the first generation of your butterfly typically flies in the spring or summer. (Keep in mind that flights can be early or late depending upon precipitation, the timing of spring, and/or the prolonging of winter, etc.) Then, I would keep pupae in their cold cycle until roughly two weeks before the mid-flight of that generation so that you will release adults right when your local populations are in mid flight.
Checkerspot butterfly caterpillars conforming to the genera Euphydryas, Chlosyne, Poladryas, and Thessalia overwinter as half-grown larvae and are gregarious before diapausing. (They usually disperse in nature to nearby plants before diapausing to insure that they will obtain sufficient isolation when resuming feeding the next spring.)
However, after these larvae overwinter and break diapause in the spring, these same larvae will feed for an instar and then re-diapause if placed either in too close of proximity to sibling caterpillars, on too little of host plant, or some combination of two.
In nature, rediapausing checkerspot larvae usually is not a problem for some California populations of Euphydryas chalcedona where the larvae feed on hearty bushes. However, there are other checkerspots that feed on smaller plants, such as Penstemon and Castilleja spp. These plants generally can only support a limited number of post-diapause larvae. Therefore, in nature, if too many post-diapause larvae are feeding on the same limited plant at the same time, some larvae will re-diapause to insure survival.
Therefore, in the lab, it makes sense both to separate post-diapause checkerspot larvae and provide plenty of host plant in order to coax them to NOT rediapause; producing adult butterflies sooner rather than later. Using the twin cup method of rearing for one checkerspot larva, is one way of addressing this problem. To see a video demonstrating the twin cup method for Thessalia leanira wrighti, click here. (Also, see slide show below.)
Because admirals and viceorys overwinter in a rolled-leaf hibernaculum, you have some options on how you want to properly overwinter these hibernacula and bring them out of a cold, humid environment into a warm, humid environment to get half-grown larvae to crawl out of their hibernacula and resume feeding.
This photo gallery shows you through one successful method of accomplishing this. For more general information on rearing Limenitis species, click here.