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Nature Notebook – Insect Diapause

Has the number of house-visiting insects finally dropped? Look outside and it will be nearly impossible to find any moving insects. Where have they gone?

They are spending the winter in diapause.  All life activities and development stop during this period.  When the temperature and, more importantly, the light-to-dark ratios of sunlight are just right they will resume their development.  In order to minimize the effects of winter, the insects will first migrate vertically.  They will move from higher places to lower, more protected places such as under leaf litter. Or, they migrate to warmer spots such as inside houses. Then they settle in for a long winter’s nap.

Outdoors many species will enter a different life stage before starting diapause (i.e. adults lay eggs, larvae form pupae).  A keen-eyed observer may spy the hardened egg case of a mantid on a bush or the messy clump of cattail fluff in which the larva of the cattail moth is resting.  Looking for these signs of life can turn a winter walk into a treasure hunt.