In Florida, it is abundant throughout the summer, but its populations decline from October to April. At 25 degrees C it develops in 13 days from egg to adult. Oval, three times longer than wide, with a small projection. It is clear and shiny, like a piece of glass. Size increases after the egg is laid.
Larva hatches two days after oviposition by the adult.
If not submerged in water, the larva dries out shortly after being dissected. Larvae are located in the host's posterior end. When they emerge from the host, they are much more rugged and immediately begin spinning a tight silky cocoon. Females bear short ovipositors and parasitize only young larvae or even eggs. In the laboratory, C. marginiventris lives more than a week, but it is most effective as a parasitoid between two and four days of age.