Recruitment to forage of bumblebees in artificial low light is less impaired in light sensitive colonies, and not only determined by external morphological parameters

- Eye morphology and worker size correlated within one colony and between colonies.
- Within a colony light sensitivity correlated with morphological parameters.
- Between colonies more factors determine light sensitivity.
- The initial foraging capacity of colonies correlated with their light sensitivity.
- Not only morphology determined bumblebees eager to forage in weak light conditions.

Bumblebees of Bombus terrestris are essential pollinators in natural and managed ecosystems. Their foraging ability relies on the individual morphology, task allocation within the colony, and external factors, such as light intensity. The foraging activities of commercial bumblebees can sometimes be impaired, especially in the artificial and weak light intensities of greenhouses at high altitudes. Here we investigated whether the eagerness (or willingness) to forage of bumblebee colonies in different light conditions is correlated with the light sensitivity of bumblebees colonies and/or different external morphological parameters. The initial foraging capacity of bumblebee colonies correlated with their light sensitivity. However, light sensitive bumblebee colonies did not necessarily had a higher foraging activity at lower light intensities. Differences in initial foraging capacity and light sensitivity among colonies could not be explained by the external morphological parameters. In conclusion, our data illustrated that the recruitment to forage in artificial low light is less impaired in light sensitive colonies, and that not only the external morphology parameters determine the light sensitivity of bumblebees and their eagerness to forage in weak light conditions. The data obtained here create a better understanding of which criteria are able to select towards light sensitive bumblebees and their link with the foraging capacity of these bumblebees.