PARTS OF INSECTS. 2^7 



tact, such an organ may be regarded as that of smell. Should the an- 

 tenna present a tissue of many nerves, what inconvenience can result 

 from supposing that this tissue is capable of transmitting odour? 

 Would not this hypothesis, on the contrary, be more simple and more 

 consonant to anatomical principles, than that which fixes the seat of 

 smell at the entrance of the stigmata? Besides, this last mode of ex- 

 planation will not, I presume, suit the crustaceous animals, which so 

 nearly approach to insects. 



" 2. Many male insects have their antennae more developed than the 

 females ; a fact easily explained, if we admit that these organs are the 

 seat of smell. 



" 3. It is certain tliat most of those insects which live or deposit 

 their eggs on putrid animal or vegetable matters, stagnant waters, or 

 any substance, in short, which, for a time, att'ects peculiar localities, 

 arc almost uniformly distinguished by a greater development of the an- 

 tenna". Such, for example, are the Scaraba-us, Dcnnestcs, Silpha, Ckrus, 

 Teiicbrio, Tipula, Bilno, 4'C- These require a more perfect sense of 

 smell, and are organized accordingly. 



" 4. A great many insects which are entirely predaceous have simple 

 antennee ; and those wliich are characterized l)y similar manners, and 

 which are sedentary, have none at all; as, for instance, the Acari, and 

 a considerable portion of Lamarck's Arucknidce. 



" 3. Insects discover their habitation and food by the sense of smell. 

 I have deprived several insects of their antenna', when they instantly 

 fell into a state of stupor or derangement, and seemed to be incapable 

 of recognising their haunts or their food, though just beside tliem. 

 Such experiments deserve to be prosecuted. I would recommend, for 

 example, the varnishing or covering the antenna; of dung beetles, and 

 placing them near animal excrements, of which they are particularly 

 fond, to observe if they would repair to them as usual. 



" G. The ner\'es terminate at the antennie; and their articulations, 

 though externally covered with a pretty thick membrane, are hollow, 

 lined within !\v a soft substance, which is often of a watery consist- 

 ency, and whose extremity', when opposed to the air, may receive its 

 impressions." 



Os, the Mouth. In order to afford some idea of the amazing dif- 

 ference that prevails in the structure of the several parts or organs 

 which constitute the mouth, it will be only requisite to observe, that 

 the classification of all insects in the Fabriciau system is founded on 

 this character. There are ten principal parts of which ihe mouth con- 

 sists ; and it is from tlie relative proportion of each, from the dissimi- 

 larity in the form, position, variation in nimiber, or occasional pecu- 

 liarities, that the most permanent characters are deduced. These parts 

 have one disadvantage; they are generally small, and from this cir- 

 fuiastance have uot been so universally adopted in the arrangement 



