If you've spent any time at all photographing insects, you've probably learned the good old fridge trick. Put an insect in your fridge for a few hours, and it will be rendered immobile. The cold temperature of the refrigerator induces a coma-like state in insects, which are ectotherms, and is fully reversible. Just set up your shot, give your subject a few minutes to thaw, and click! You've got your shot.
Biologists at Western University finally figured out what causes this paralysis in chilled crickets - an imbalance of water and sodium. When the temperature drops, "water and sodium move from the insect blood, called hemolymph, into their gut," according to Heath MacMillan, lead investigator on the study. "This is bad for the insect because it concentrates potassium in the blood that remains, which leaves muscles unable to function."
When the crickets needed to move again, they first restored the concentration of potassium in the hemolymph. It took time, however, for the insects to return to their normal physiological state, with water and sodium back in balance. "We measured the metabolic cost of this reboot and found that the process increased a cricket's metabolic rate by as much as 50 per cent for a few hours," reports MacMillan.
Source: Chillcoma, Department of Biology, Western University