steinernematids

Steinernematids are a genus of entomopathogenic nematodes, meaning they are microscopic roundworms that parasitize insects. They are widely distributed in soil and are known for their ability to control insect pests in agriculture and forestry. These nematodes have a symbiotic relationship with specific species of bacteria, primarily from the genera Xenorhabdus and Photorhabdus. When a steinernematid infects an insect, it releases these bacteria into the insect's hemocoel. The bacteria multiply rapidly, causing septicemia and killing the insect. The nematodes then feed on the liquefied insect tissues and the bacteria, reproduce, and eventually emerge from the cadaver to seek new hosts.

The life cycle of steinernematids involves several stages, including egg, four larval stages, and adult. The infective stage is the third larval stage, known as the dauer larva. This stage is highly resilient and can survive in the soil for extended periods until it encounters a suitable insect host. Upon entering the insect, the dauer larva molts and develops into the fourth larval stage, then into an adult. Adults mate and lay eggs, which hatch into new larvae. Under favorable conditions, the cycle can be completed within a few days. Steinernematids are important biological control agents due to their specificity to insects and their ability to break down quickly in the environment, posing no threat to non-target organisms.