Yellow jackets (Vespula species) are social wasps known for aggressively defending their colony and their presence at outdoor gatherings. These insects are active during the day, leading people to wonder about their state of rest during the dark hours. The concept of “sleep” in these wasps is much different from the sleep experienced by humans, involving a distinct biological state to achieve necessary rest.
Defining Rest in Insects
Yellow jackets and other insects do not experience “sleep” like mammals, as they lack the complex brain structures necessary for rapid eye movement (REM) cycles. Instead, insects enter quiescence, which serves a similar restorative function. This state is characterized by prolonged immobility and a noticeable decrease in responsiveness to external stimuli.
During quiescence, a yellow jacket’s metabolism slows down, and its body temperature may decrease, reflecting a reduction in physiological activity. This state is distinguishable from simple inactivity because the insect exhibits an increased arousal threshold, though it is easily reversible upon stimulation. This necessary downtime allows for biological maintenance, even without the deep unconsciousness associated with human sleep.
Where Yellow Jackets Go at Night
Yellow jackets are strictly diurnal, meaning foraging and construction only happen during daylight hours. As dusk approaches and ambient temperatures drop, worker wasps cease outdoor activity and return to the communal nest structure. This behavior is partly due to their poor night vision, making them ineffective at navigating or hunting in the dark.
The entire colony congregates inside the protected paper nest, typically located in an underground burrow, a tree cavity, or a structural void. Inside the nest, the workers settle into quiescence, often clinging to the paper comb or resting on the inner walls. Because the colony is present and less active at night, this window is when they are most vulnerable to outside threats.
Seasonal Colony Shutdown
The daily cycle of activity is separate from the long-term cessation of activity that occurs with the change of seasons. In temperate climates, yellow jacket colonies are annual and do not survive the winter as a unit. As temperatures drop in late fall, the majority of the colony, including workers and the old queen, perish.
Only newly fertilized queens, produced late in the season, survive to start the next year’s colony. These new queens seek a sheltered location, such as under tree bark, in a hollow log, or within a wall void, to enter a true state of hibernation called diapause. Diapause is a pre-programmed developmental arrest, distinct from daily quiescence, where the queen’s metabolism drastically slows down to conserve energy until spring returns.