Howardula nematodes can severely impact fly egg development, as infection can effectively sterilize some species.
These nematodes are used as biological control agents, as they efficiently kill their insect prey within days after infection.
However unlike these nematodes, Howardula aoronymphium requires its host fly to survive into adulthood, and does not increase larval mortality.
[3] Moreover Howardula aoronymphium is quite specific to mushroom-feeding flies, while other insect-infecting nematodes can be more generalist worms capable of infecting a wide variety of insects.
The inherited bacterial symbiont Spiroplasma poulsonii can defend flies against Howardula infection by attacking the nematodes using toxins analogous to sarcin or ricin.