# The Honey Bee Colony’s Criterion for Candidate Selection: “Ongoing” or “One-Shot”?

## TL;DR

Honey bee colonies select queen candidates based on quality rather than nepotism, optimizing queen rearing through a multi-stage process.

## Contribution

This study reveals that honey bee colonies use a quality-based, multi-stage selection process for queen candidates in the absence of nepotism.

## Key findings

- Colonies prefer 1-day-old larvae for queen rearing, with higher survival and gene expression related to reproductive quality.
- Queen selection is optimized through stages (larval, capping, emerging), eliminating lower-quality candidates.
- Emerging queens from 1-day-old larvae attract more worker followers, indicating superior quality.

## Abstract

The honey bee is a typical social insect, and a colony is composed of a queen, workers, and drones. The queen is responsible for reproduction and is essential for the development of the colony. When the queen dies or is injured, workers raise closely related larvae to develop into a queen. Without nepotism, how do colonies choose queen candidates during emergency queen rearing? Are there criteria for queen candidates? Is the colony’s criterion for candidate selection “ongoing” or “one-shot”? Our investigation focused on the emergency queen-rearing process in a natural colony (without nepotism), where we observed and documented the selection of queen candidates from different stages (the larval stage, capping stage, and emerging stage). We examined the physiological indicators and the expression of ovarian development-related genes (vg, hex110, and Jh), and found that the colony would eliminate queens of low reproductive quality and prefer queens with higher reproductive ability. While the exact mechanism by which workers assess queen candidates’ quality is unknown, the result of this layered filtering of investments in queen candidates may be to maximize colony growth. In the absence of nepotism, the selection of queen candidates is not final but is gradually optimized.

In the honey bee, the queen’s death severely threatens the survival of the colony. In an emergency, new queens are reared from young worker larvae, where nepotism is thought to influence the choice of queen candidates by the workers. This article simulates the emergency queen-rearing process in a colony under natural conditions and records the results of colony selection (without nepotism). In queenless colonies, worker larvae aged three days or younger were preferred for queen rearing, and 1-day-old larvae were the first to be selected for the queen-cell cups. In the capping stage, the number of capped queen cells selected from the 1-day-old larvae was much higher than the 3-day-old larvae. On the first day, the number of emerging queens reared from 1-day-old larvae was significantly higher than the queens reared from 2-day-old and 3-day-old larvae. However, there was no significant difference in the birth weights of queens reared from 1-day-old, 2-day-old, or 3-day-old larvae. When the newly emerged queens were introduced into the original queenless colony, 1-day-old larval queens triggered more worker followers than 2-day-old larval queens. The expression of ovarian development-related genes (vg, hex110, and Jh) was higher in queens reared from 1-day-old larvae than those reared from 2-day-old and 3-day-old larvae, indicating that the quality of the queens reared from 1-day-old larvae is superior. This study shows that in the absence of nepotism, the colony selection of queen candidates at the larval stage, capping stage, and emerging stage is not final, but is gradually optimized to maximize colony development through a “quality control” process.