Control of Salivation in the Blowfly Calliphora

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Abstract
A technique has been developed for collecting saliva from the salivary duct of flies during feeding. In newly emerged flies salivation is evoked by stimulation of the labellar taste papillae by crystalline sugar, by sugar in solution and by water. Only sugars which excite the sugar receptors are effective. In flies which have previously fed, solid sucrose or meat induce regurgitation of the crop contents, or salivation if the crop is empty. Sucrose in solution provokes neither reaction. Saliva always contains digestive enzymes, even if the ingested food requires no digestion. Blood taken from salivating flies stimulates fluid secretion from isolated glands, whereas blood taken from non-salivating flies is ineffective. Section of the cephalo-thoracic nerve cord abolishes salivation in response to feeding. Section of the ventral nerve cord posterior to the thoracic ganglion, or removal of the abdomen, severely reduces but does not abolish the salivatory response. Saliva secreted by mature flies contains 75 mM-Cl− whereas saliva secreted during the first meal after emergence has a higher Cl− concentration (about 165 mM-Cl−) which gradually declines during the first meal.