Maybe you frooze them in that state so they could not die...ha ha. Did they come back to life after thawing them out? I even asked the guy at the bait shop and he said he wished he new also.....I buy a hundred and maybe use 1/2 before the rest turn to cocoons.
Funny Story.... last trip of the year once I left my spikes in my pocket in there container. Pulled my ice fishing gear out the next year and I realized I left my tin of spikes in my pocket from last year. Opened it up and had a bunch of what looked like dead house flies in the container.