Host specific social parasites (Psithyrus) indicate chemical recognition system in bumblebees

Area of Science:

• Chemical Ecology
• Insect Behavior
• Evolutionary Biology

Background:

• Semiochemicals mediate crucial insect behaviors, particularly host-parasite interactions.
• Bumblebees (Bombus) and their social parasites, cuckoo bees (subgenus Psithyrus), offer a model system to study chemical recognition.

Purpose of the Study:

• To investigate the chemical recognition system of bumblebees.
• To analyze the cuticular hydrocarbon cues of bumblebee species and their cuckoo parasites.
• To understand the chemical strategies employed by cuckoo bees for host invasion.

Main Methods:

• Analysis of cuticular hydrocarbon profiles from 14 bumblebee species, including five cuckoo bee species.
• Comparison of alkene positional isomer profiles between host bumblebees and cuckoo parasites.
• Identification of chemical repellents used by cuckoo bees in specific host-parasite associations.

Main Results:

• Bumblebees exhibit species-specific alkene positional isomer profiles, consistent across large geographic areas.
• Host-specific cuckoo parasites effectively mimic these bumblebee hydrocarbon profiles.
• In cases of poor mimicry, likely due to recent host shifts, cuckoo bees utilize dodecyl acetate, a chemical repellent, for colony invasion.

Conclusions:

• Cuckoo bees employ dual chemical strategies—mimicry and repellents—to infiltrate host bumblebee colonies.
• These distinct invasion mechanisms may represent different stages in a dynamic evolutionary arms race between hosts and parasites.