Surviving the Winter

Squash bugs, Anasa tristis

The squash bug, Anasa tristis, only survives on squash plants which in Indiana, are unavailable from Autumn to late Spring. Squash bugs survive this period of inhospitable weather and lack of food by diapause. To prepare to overwinter, adult squash bugs find shelter from the worst elements, typically under leaves or other plant litter.

Diapause is conditioned in squash bug by the declining daylight in Autumn and the lack of food. The diapause is a period of extremely low metabolic activity. The insect enters a low activity state and becomes unresponsive to outside stimuli. Utilization of stored food to produce energy is minimized. Consumption of oxygen, that is used to produce energy, declines to low levels. Energy production yields carbon dioxide and water and the metabolic water production is reduced. The insect is not drinking and must conserve water.

The squash bug is adapted to prevent water loss. The cuticle is an important barrier to water loss. Diapausing insects may produce a thicker wax layer to better reduce water loss. The respiratory system is another source of water loss. The spiracles, that control the opening of the respiratory are held shut. A diapausing insect needs little oxygen and produces little carbon dioxide so there is less need to open the spiracles.

The squash bug is tightly sealed, suspending activity until conditions are more favorable (and your squash plants are growing) before they become active in late Spring.