Page:Jardine Naturalist's library Entomology.djvu/143

Rh circulation; their secreting and excreting organs are usually long, slender, and tubular vessels, floating freely in the interior of the body. The salivary vessels are most conspicuous among suctorial insects, but they likewise exist in others. They generally lie around the pharynx or the crop, and ascend into the cavity of the mouth by a meandering duct. Under all their changes of form, we can, without much difficulty, according to M. Léon Dufour, recognise the following parts: 1. A glandular apparatus destined to secrete saliva, which is single, double, or even triple; 2. One or two excretory conduits, whose function it is to discharge the secreted liquid into the mouth or esophagus; 3. Bags or reservoirs in which the saliva is deposited and preserved. In Scutellera nigrolineata, the figure of which we have copied from the author just named, all these parts are distinctly exhibited. Pl. II. fig. 5, a, a, represents a large semi-diaphanous glandular piece, (greatly resembling a true gland,) composed of two lobes, the hinder of which is digitated; from each of these issues a very flexuose excretory duct, which debouches into the esophagus, (b, b.) The salivary reservoirs are, in this instance, slender and twisted, as is very often the case; (c, c.) Cicada orni presents a different arrangement, the secreting organs consisting of a mass of minute oval bags or bladders, divided into two bundles, which are united by means of a tubular canal; (Pl. II. fig. 6, a, a.) The anterior of these