OF INSECTS. 
137 
circulation ; their secreting and excreting organs are 
usually long, slender, and tubular vessels, floating 
freesly in the interior of the body. The salivary ves- 
sels arc 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 Du four,* 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 s, the figure of which we have copied from 
the author just named, all these parts are distinctly 
exhibited. PI. 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 ; (PI. II. fig. fl, a } a.) The anterior of these 
*‘See his excellent work entitled, “ Becherches Anatomiques 
$ur les flenripteres, p. 119. 
