Microorganismal Cues Involved in Host-Location in Asilidae Parasitoids

Area of Science:

• Behavioral Ecology
• Chemical Ecology
• Insect-Microbe Interactions

Background:

• Parasitoids are insects that kill their host during development.
• Atypical parasitoids, including some Diptera (flies), possess larvae that actively locate hosts.
• Host-seeking behavior in these larvae relies on detecting chemical cues.

Purpose of the Study:

• To investigate the chemical cues used by parasitoid larvae of the genus Mallophora for host detection.
• To explore the role of microorganisms in mediating host orientation.
• To assess potential host competition among Mallophora species.

Main Methods:

• Olfactometry assays were conducted to evaluate host-seeking behavior.
• Potential hosts were treated with antibiotics to assess microbial influence.
• Larval attraction to host frass was tested.
• Behavioral responses to a common host species were observed under interspecific competition scenarios.

Main Results:

• Two Mallophora species demonstrated orientation towards different host species.
• Chemical cues involved in host attraction are produced by microorganisms.
• Antibiotic treatment reduced host attractiveness for M. ruficauda but not M. bigoti, suggesting different microbial locations.
• M. bigoti was attracted to frass from a common host.
• Both species oriented to the same host (Cyclocephala signaticollis), indicating potential field competition.

Conclusions:

• Microorganisms play a crucial role in mediating host orientation for Mallophora parasitoid larvae.
• Variations in microbial activity or location within the host influence cue attractiveness.
• This study confirms the parasitoid lifestyle for M. bigoti and reinforces it for all Mallophora species.