Blister beetle larvae have been shown to emit volatile compounds that closely resemble floral scents, enabling them to attract bees and gain access to their nests. The findings, reported in a preprint, describe the first known case of an animal chemically mimicking the smell of flowers to manipulate pollinators.
The study focuses on larvae of the European black oil beetle (Meloe proscarabaeus), a parasitic species whose early life stage depends on attaching to solitary bees for transport to their nests. After hatching, the larvae aggregate on grass stems and latch onto visiting bees, which inadvertently transport them back to their nests. Once inside, the larvae consume the bee’s egg and stored provisions.
To investigate how the larvae attract their hosts, researchers at the Max Planck Institute for Chemical Ecology analyzed volatile compounds released by larval aggregations. Using headspace solid-phase microextraction coupled with gas chromatography–electron ionization mass spectrometry (HS-SPME GC-EI-MS), the team identified a mixture of monoterpenoid volatiles derived from (S)-linalool, including linalool, linalool oxides, and lilac aldehydes – compounds commonly associated with floral scent but rarely reported in insects.
Chiral GC-EI-MS confirmed that the larvae emit only the (S)-enantiomer of linalool and its derivatives, matching the stereochemistry found in many flowering plants. Behavioral assays using Y-tube olfactometers showed that both male and female bees preferred the larval scent over plant controls, indicating that the volatiles function as generalized floral cues rather than sex pheromone mimics.
The researchers also examined how the larvae produce these compounds. Transcriptomic analysis identified cytochrome P450 enzymes that were strongly expressed in larvae but not in adult beetles. Functional expression of candidate enzymes in Saccharomyces cerevisiae, followed by GC-EI-MS analysis, showed that two P450s oxidize (S)-linalool into the monoterpenoids detected in larval emissions.
The authors suggest that emission of floral-scent volatiles enables M. proscarabaeus larvae to attract female bees directly, improving access to suitable nests without intermediary hosts. Identification of the underlying cytochrome P450 pathways points to a wider, and potentially underexplored, role for plant-like volatiles in insect chemical ecology.
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