Do Bumble Bees Produce Brood Pheromones?

Area of Science:

• Social insect behavior
• Reproductive division of labor
• Chemical communication

Background:

• Reproductive division of labor is key in social insects, regulated by behavior and chemicals.
• Primitive eusocial species may rely more on behavior, while advanced species use pheromones.
• Worker reproduction in Bombus impatiens is inhibited by larvae and triggered by pupae, but the mechanism is unknown.

Purpose of the Study:

• To investigate if brood pheromones regulate worker reproduction in the primitively eusocial bumble bee, Bombus impatiens.
• To determine if olfactory cues from larvae and pupae inhibit worker egg-laying.
• To assess if workers can detect larval starvation via olfactory cues.

Main Methods:

• Choice experiments to assess behavioral attraction of workers to larvae and pupae.
• Experiments to measure worker egg-laying in the presence of odors from larvae and pupae.
• Olfactory choice experiments to test worker discrimination between starved and fed larvae.

Main Results:

• Workers showed behavioral attraction to pupae over larvae, aligning with reproductive interests.
• Odors from larvae or pupae alone were insufficient to inhibit worker reproduction.
• Workers could not differentiate between starved and fed larvae based on olfactory cues.

Conclusions:

• Olfactory signals from brood are not the primary regulators of worker reproduction in Bombus impatiens.
• Workers can distinguish between developmental stages (larvae vs. pupae) but not nutritional status of larvae.
• Reproductive decisions in bumble bee workers likely involve multiple sensory inputs or behavioral interactions, consistent with their simple social structure.