Control of midgut invertase activity in Periplaneta americana: The possible non-exocrine role of the salivary glands

When the salivary glands of 10-day-old adult Periplaneta americana L. are removed, a gradual decline in midgut invertase activity is found. No such effect occurs in cockroaches whose salivary ducts are severed. An injection of salivary gland extract in the haemocoel of salivarectomized insects causes the reestablishment, to a large extent, of the normal midgut enzyme levels. The possibility of the involvement of a non-exocrine factor from the salivary glands is discussed.