OF INSECTS. 137 



circulation ; their secreting and excreting organs are 

 usually long, slender, and tubular vessels, floating 

 freely in the interior of the body. The salivary ves- 

 sels 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. Un- 

 der all their changes of form, we can, without much 

 difficulty, according to M. Leon Dufour,* recognise 

 the following parts: 1. A glandular apparatus des- 

 tined 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, .) 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 



* See his excellent work entitled, " Recherches Anatomique* 

 sur les flemipteres, p. 119. 



