Work was also being done in the realm of parasitology and the study of worms. A French physician named Nicolas Andry de Bois-Regard determined that worms were the cause of some diseases. He also declared that worms do not spontaneously form within the animal or human gut; de Bois-Regard stated that there must be some kind of 'seed' which enters the body and contains the worm in some form. Antonio Vallisneri also worked with parasitic worms, specifically members of the genera "Ascaris" and "Neoascaris". He found that these worms came from eggs. In addition, Vallisneri worked to elucidate the reproduction of insects, specifically the sawfly.