Diapause

A winter population of butterflies is really hard to upkeep, especially after 2 nights of hard freeze! This morning in the Flight Encounter I spotted 4 butterflies. Two monarchs, two polydamas swallowtails and a bonus Oleander moth. Luckily, my tank full of monarch caterpillars has mostly gone to chrysalis and should bolster the chilly population in 10-14 days. I will celebrate their hatching.

Surviving over winter is tough for butterflies since they are poikilotherms (of varying temperature) and are very much subject to outdoor temperatures. Butterflies and moths have some small ways they can help control their temperature like shivering their flight muscles to provide some warmth, but they are still very much subject to cold temperatures which make them sluggish or torpid.

Some butterflies will migrate to warmer areas in the winter, like the well described migration of monarchs to forests of Mexico. Others like the tortoiseshells and anglewings may overwinter as adults using man-made or natural crevice type structures in which to hibernate and shelter.

Some butterflies in various stages of development utilize diapause to overwinter. Diapause is a state of dormancy in which all development is suspended. Unlike hibernation where development and metabolism still occur at a slower rate, during diapause all cellular growth stops causing complete dormancy.

Triggered by a number of factors including length of daylight hours, temperature and possibly even the angle of sunlight which may indicate the approach of unfavorable conditions a butterfly may enter into the state of diapause.

A pupa entering diapause will cease development and the metamorphosis of the insect inside will halt until conditions become more favorable to the survival of the insect. The only energy used upkeeps the integrity of cells from breaking down, but does not cause cells to change, reproduce, or grow. A caterpillar in diapause will cease eating, growing, shedding or burning food-fuel that has been stored. They basically just stop.

Diapause is a true suspended animation.

Check out more on diapause:

Diapasure research foundation

and Longest Diapause among insects from IFAS