Farm Horizons, February 2014

Diapause in creatures

By Christine Schlueter
McLeod CountyMaster Gardener

Where do the creatures go in winter?

The ground is alive with myriads of ants, bugs, beetles, caterpillars, and smaller forms of insect life.

Inevitably there comes a night when the temperature drops much below the freezing point and the vegetation is thickly coated with frost.

On the following day, no insects are seen or heard. Where did they go?

The thing about insects is that they do not have body fat like bears or gophers, to survive freezing temperatures and keep internal fluids from turning to ice. Insects need a way to cope with the ups and downs of temperatures in their environment.

A few species of butterflies and moths migrated sout earlier in autumn: notably the Monarch butterfly – sometimes in vast flocks, sometimes as far as the West Indies – and some of them, tattered and worn, return in spring to lay eggs on young milkweeds.

Adult angle-winged butterflies, such as the Mourning Cloak and Red Admiral, hibernate in outbuildings or hollow trees and become torpid, but on balmy winter days, may emerge and flutter aimlessly about. Others just stay in the pupa stage until spring.

The grasshoppers died. So did all but a few species of butterflies, moths, and the adults of many other kinds of insects whose young, however, pass through winter in the egg stage or hibernate as larvae, pupae, or nymphs.

The ants huddle in their burrows. The honeybees huddle in their hives. The bumblebee queens and the queens of colonies of social wasps have crept into protected places where they hibernate until spring, but the males and workers died. There is warmth in numbers and being close to each other.

Those that hibernate in the ground have to find a place where they can go below the depth of the soil that freezes above.

All of the male mosquitoes died. Fertilized females of the common house mosquito congregated in cellars, catch-basins, hollow trees, and other protected places where they hibernate. The woodland and floodwater mosquitoes winter over as eggs.

Other insects are seeking places to hibernate and manage to creep through cracks and invade our homes: houseflies, the bluebottle and greenbottle blowflies, wasps, lady beetles, and that harmless nuisance the boxelder bug. Usually, when it is cold, they hibernate in clusters to keep warm.

Some kinds of adult insects can endure long periods of extreme cold while hibernating if those periods are continuous – not interrupted by warm thawing days, and some, believe it or not, survive being frozen.

This is a state called diapause which basically means “sleep time,” which is different than hibernation because there is no growth during this time.

There are two kinds of diapause:

Obligatory, which means that an animal or insect must do this at some stage in its development and has no choice in doing so.

Facultative meaning that sleeping is because something bad is going to happen. This is different than other kinds of hibernation that happen after something bad happens. With facultative diapause, the creature goes to sleep before drought or cold winter.

It really is all in the genes of the animal or creature. They instinctively do what their body tells them to do. It is interesting to find out what each type does, and why.

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