INSECTS m GENERAL. 79 



night, answer the same purpose. Many exhale peculiar 

 odours, by which they are discovered at a distance by the 

 opposite sex. 



The configuration of the male and female organs varies 

 too much, not only in the orders, but also in the genera, and 

 even in the species, to enable us to prevent any general 

 notion of it. We shall merely mention that the spermatic 

 vessels are very numerous in the males, and very much 

 inflated at certain times. These vessels, which are twelve 

 or fifteen times the length of the body, are folded and 

 re-folded on themselves, so as to occupy a considerable por- 

 tion of the cavity of the abdomen. They lead to a common 

 reservoir, or vesiculae seminales, which have been compared 

 to prostates, to epididymes, to vasa deferentia, &c. 



Instruments are often found in the females which facilitate 

 the laying of the eggs, or the various modes in which they 

 ought to be deposited. These are the ovipositors (Kirby). 

 The vulva opens into the cloaca ; thither the oviducts lead. 

 These are very elongated canals ; like the spermatic vessels, 

 but much more bulky. The eggs are distinguished there, 

 and so much the more developed, as they are nearer the com- 

 mon canal which leads into the cloaca. 



It is most frequently in this common canal that they re- 

 ceive the glue or viscous humour, which serves to fix or 

 suspend them, by pedicles sometimes very elongated, as may 

 be observed in the eggs of hemerobias. There are insects 

 which lay all their eggs at once, like two bunches of grapes, 

 which is the case with the ephemera ; but in general, these 

 eggs pass successively one by one, through the orifice of the 

 cloaca. The ovipositors have various forms, of knives, sabres, 

 saws, gimlets, probes, &c. 



In this, as in the proper place, we shall briefly notice the 

 general phenomena of insect metamorphoses. The metamor- 

 phoses of insects were imperfectly known by the ancients. 



