Reproductive secrets of a cricket-hunting parasitoid fly

A recent study published in the Annals of the Entomological Society of America provides the most comprehensive insight to date into the development of this atypical fly and its live birth—a uncommon occurrence among flies. Undergraduate student Parker Henderson ‘22 from St. Olaf College spearheaded the project, which unveiled significant findings regarding the reproductive biology of Ormia ochracea, a parasitic fly renowned for its hyperacute directional hearing that enables it to locate chirping crickets.

The scientists utilised dissection, fluorescence labelling, and microscopy to describe the manner in which female O. ochracea carry developing embryos in a uterus-like structure and provide internal nourishment until they hatch as fully developed larvae. The larvae are thereafter put directly onto host crickets, infiltrate their bodies, and undergo growth within the cricket, ultimately resulting in the host’s demise.

Viviparity and Parthenogenesis: A Complex Reproductive Strategy

The study elucidates the significant growth of embryos in utero, presumably acquiring maternal sustenance during development, a reproductive strategy termed adenotrophic viviparity. It also demonstrates an unexpected ability for partial parthenogenesis: unfertilised ova from virgin females initiate early developmental phases, including nuclear division and basic patterning, although they do not achieve complete larval formation. The team examines how this internal embryonic development presents technological obstacles for genetic manipulation, suggesting that future genetic tools may need to focus on sperm instead of eggs.

“This work highlights an extraordinary and underappreciated side of Ormia biology,” stated Eric Cole, a senior author and professor of biology at St. Olaf College. “The complexity of their reproductive strategy raises fascinating questions about insect development and host-parasite evolution.”

Broader scientific impact and student contributions

Comprehending the reproductive mechanisms and host interactions of parasites such as O. ochracea enhances scientists’ understanding of wider ecological and evolutionary processes, pertinent to agriculture, disease transmission, and pest management. Insights from this system may enhance biological models of developmental biology, reproductive methods, and bio-inspired technologies. Indeed, Ormia’s directional auditory perception has already impacted the design of hearing aids and the advancement of acoustic sensors. Furthermore, involving undergraduates in this type of research enhances scientific literacy and public comprehension of science.

For Henderson, who finalised the study during his undergraduate research training, the experience was profound. “Leading this project made me realize that I want to pursue a career in scientific research,” he stated. “This kind of hands-on work is what brings science to life. It’s how you learn to think like a scientist and contribute to new knowledge.”

Henderson is a co-author of a supplementary publication from the Lee Lab of Neural Systems and Behaviour, directed by Norman Lee, an associate professor and head of the neuroscience program. Published in the same edition of the Annals of the Entomological Society of America, the study examines the impact of resource competition among larvae on the developmental outcomes of Ormia ochracea, thereby enhancing our comprehension of this species’ intricate life history and ecology. Access additional information here.

The investigation of reproductive architecture and embryogenesis received funding from the National Science Foundation, with Cole and Lee acting as senior authors. Both academics underscored that undergraduate research experiences are crucial for the advancement of science and the preparation of future STEM professionals.

“Undergraduate research doesn’t just produce meaningful discoveries. It cultivates future scientists,” Lee stated. “Continued investment in student research is essential to both the scientific enterprise and to building a more capable STEM workforce.”

He stated, “The findings also lay the groundwork for future genetic and developmental research in Ormia, a species already well-known in neuroethology for its miniature, highly directional auditory system and precise host-seeking behavior.”

Original Publication
Authors: Parker Allen Henderson, Margaret Bloch Qazi, Norman Lee and Eric S Cole.
Journal: Annals of the Entomological Society of America
DOI: 10.1093/aesa/saaf021
Method of Research: Observational study
Subject of Research: Animals
Article Title: Reproductive anatomy and embryogenesis of a viviparous, phonotactic, parasitoid fly
Article Publication Date: 10-Jul-2025