New study reveals surprising reproductive secrets of a cricket-hunting parasitoid fly

A new study published in the Annals of the Entomological Society of America, offers the most detailed view to date of how this unusual fly develops and gives live birth—a rare phenomenon among flies. Led by undergraduate student Parker Henderson ‘22 of St. Olaf College, the study revealed remarkable insights into the reproductive biology of Ormia ochracea, a parasitic fly known for its ability to locate singing crickets using hyperacute directional hearing.

Using a combination of dissection, fluorescence staining, and microscopy, the team documented how female O. ochracea carry developing embryos in a uterus-like structure and nourish them internally until they hatch as fully formed larvae. These larvae are then deposited directly onto host crickets, burrow inside, and complete their development within the cricket’s body, ultimately killing the host.

The study describes how the embryos grow substantially in utero, likely receiving maternal nourishment during development, a reproductive mode known as adenotrophic viviparity. It also reveals a surprising capacity for partial parthenogenesis: unfertilized eggs from virgin females undergo early stages of development, including nuclear division and rudimentary patterning, though they did not complete larval formation. The team also discusses how this internal embryonic development poses technical challenges for genetic manipulation, raising the possibility that future genetic tools may need to target sperm rather than eggs.

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

Understanding how parasites like O. ochracea reproduce and interact with their hosts helps scientists better grasp broader ecological and evolutionary dynamics, including those relevant to agriculture, disease vectors, and pest control. Insights from this system may also inform biomedical models of developmental biology, reproductive strategies, and even bio-inspired technologies. In fact, Ormia’s directional hearing has already influenced hearing aid design and acoustic sensor development. Moreover, engaging undergraduates in this kind of research strengthens scientific literacy and public understanding of science.

For Henderson, who completed the project as part of his undergraduate research training, the experience was transformative. “Leading this project made me realize that I want to pursue a career in scientific research,” he said. “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 also a co-author on a companion paper from the Lee Lab of Neural Systems and Behavior, led by Norman Lee, an associate professor and director of the neuroscience program. Published in the same issue of Annals of the Entomological Society of America, that study investigates how resource competition among larvae affects developmental outcomes in Ormia ochracea, further expanding our understanding of this species’ complex life history and ecology. Read more here.

The reproductive anatomy and embryogenesis study was supported by the National Science Foundation, with Cole and Lee serving as senior authors. Both faculty emphasized that undergraduate research experiences like this are essential for advancing science and preparing the next generation of STEM professionals.

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

He added, “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.”