The process, known as maternal offloading, is the first documented evidence of this response in honeybees.

Researchers say it may help queens reduce their own chemical burden, but could expose developing offspring to harmful levels of pesticides. The findings were published in Current Biology.

Worker bees normally protect the colony by filtering contaminants from food before they reach the queen and developing larvae.

However, the study found that this protection can become less effective as pesticide exposure continues.

Researchers created small experimental colonies containing one queen and 60 worker bees.

The bees were given food contaminated with methyl parathion, a pesticide carrying a low-level radioactive marker that allowed scientists to track its movement.

On the first day, workers filtered out 95% of the pesticide and deposited it in the honeycomb.

By the 10th day, their filtering rate had dropped to 86%, suggesting that the colony’s protective system can eventually become overwhelmed.

As pesticide contamination accumulated in the queens, some of it was transferred to their eggs.

Researchers say this could become a serious concern if pesticide levels in eggs become high enough to interfere with normal development.

Sascha Nicklisch, the study’s senior author, warned that there could be a tipping point where heavily contaminated eggs fail to develop properly, potentially contributing to a gradual decline in colony health.

The researchers used biological accelerator mass spectrometry to track extremely small amounts of the pesticide.

They noted that the pesticide concentrations used in the experiment were not lethal and were environmentally relevant.

Honeybee queens can lay between 1,500 and 2,000 eggs per day, making their health essential to colony survival.

Honeybees also pollinate about one-third of the world’s food crops, meaning threats to their colonies could have wider implications for agriculture and food security.

Researchers say further studies are needed to determine how long queens can transfer pesticides to their eggs, the long-term effects on colonies and whether the process occurs with other pesticides.