LINN^AN SYSTEM. INSECTS. 1 57 



struments of sensation. They are destitute of external 

 nosMls and ears, though some of them evidently enjoy 

 the senses of hearing and smell. 1. The eyes are 

 usually two, sometimes more, without eyelids^ and rarely 

 placed on a movable peduncle. 2. The antenncB are 

 two, placed on the head, usually before the eyes : they 

 are composed of an indefinite number of articulations, 

 and convey an unknown sensation, probably that of 

 the touch. 3. The feelers are sensorial, movable, 

 affixed to the mouth, generally four, sometimes two or 

 six; and consist of two, four, or six joints. 4. The 

 mouth is generally placed beneath the head, sometimes 

 in the breast, and in a few is wanting : the jaws are 

 transverse, and movable laterally. 5. The stemmaia 

 are three shining spots placed on the crown. 6. The 

 trunk is placed between the head and abdomen, sup- 

 ported by the feet, with the thorax above; behind which 

 is the scutel, or escutcheon, and the sternum and 

 breast beneath. 7- The abdomen is usually annulate, 

 with five segments ; perforated at the sides with five 

 spiracles, or breathing holes, with the hack above and 

 the helLy beneath ; and is terminated by the tail, which is 

 sometimes armed with a sting. 8. The wings are 0, or 

 two or four : the upper ones are often crustaceous shells, 

 covering the lower ; sometimes semi-crustaceous wing- 

 cases, or of a substance between the membranaceous wings 

 and crustaceous shells. 9- The legs consist of three 

 distinct divisions, viz. the thighs, shanks, and tarsi, 

 which are articulated, and terminated by nails : some 

 have a hand, or chelate kind of claw, with a movable 

 thumb. 10. The poisers are composed of a head, af- 

 fixed to a small pedicle, and placed under the wings of 

 the dipterous order, or such as have but two wings. So 

 far for the parts of insects. 



(211.) The changes, or metamorphoses, of what 

 Linnaeus considered insects, are thus spoken of : — Most 

 of them undergo a triple metamorphosis or transform- 

 ation, effected by casting ofi" the different coats or cover- 

 ings in which the perfect insect is inveloped. The egg 



