The salivary glands are the modified nephridia of the segment of the oral papillae.
Of the salivary glands the parotid is by far the largest, elongated in the vertical direction, and narrower in the middle than at either end.
They enclose the jaws (j), mouth (M), and opening of the salivary glands (o.·), and so give rise to the buccal cavity.
The jaw somite also disappears; the oral papilla somite forms ventrally the salivary glands, which are thus serially homologous with nephridia.
In 1898 it was conclusively shown in Italy that if a mosquito E of the Anopheles variety bites a person suffering from malaria, and is kept long enough for the parasite to develop in the salivary gland, and is then allowed to bite a healthy person, the latter will in due time develop malaria.