354 ON THE ORDERS 



proves the right of the Ametabola to form part of the true 

 Annulose division. They seem all to breathe by means of 

 stigmata, or at least have a system of respiration which 

 corresponds more with that of the larva? of insects than with 

 any other known. They have a thorax also, which, like that 

 of true insects, is composed of the first three annular seg- 

 ments of the body, which follow immediately after the 

 head. When any of the Ametabola have true feet they 

 are constantly six in number, and each of the thoracic 

 segments carries a pair. All the other feet, such as those 

 which occur in the Chilognatha and Chilopoda, are the 

 result of an abortive metamorphosis. 



The mouth of the Thysanura is constructed like that of 

 a Coleopterous insect, that is, it contains a labrum, two 

 mandibles, two palpigerous maxillae, and a labium, bear- 

 ing two palpi. M. Savigny has likewise discovered that 

 the genus Ricinus of Degeer possesses a mouth similarly 

 composed, although the palpi are not so much developed. 

 Some of this last mentioned genus, which, from the name of 

 Ricinus being preoccupied in Botany, has been lately termed 

 Nirmus (perhaps properly, since this is not the significa- 

 tion given by the ancients to the word Ricinus), have exactly 

 the shape of a Coleopterous insect destitute of its elytra 

 and wings. The Ricinus Sterna, of Linneeus is a good 

 example of this circumstance, as may be perceived on the 

 inspection of Degeer's figure, vol. vii. pi. 4. fig. 12.— 

 With the exception of its being destitute of elytra, it re- 

 sembles exactly some of the Corticarious Coleoptera. 



One of the best characteristics of the Coleoptera may be 

 founded on the fact of the anterior segment of the trunk, or 

 that Avhich precedes the wings and is called the thorax, 

 supporting the first pair of feet and being much larger than 



