CLASS OF INSECTS. 13 



12. By an examination of the preceding table we learn : that 

 animals of the class INSECTA have articulated extremities, tracheae' 

 for breathing air, white blood, but no circulatory apparatus pro- 

 perly so called. They generally have wings and three pairs of 

 legs. The head is distinct from the thorax : 



13. That animals of the class MYRI'APODA have twenty-four 

 or a greater number of pairs of articulated extremities ; no wings ; 

 white blood, but no circulatory apparatus; and that they breathe 

 by tracheae. The head, thorax, and abdomen are confounded in 

 an elongated body : 



14. That animals of the class ARACH'NIDA have white blood, 

 and generally a tolerably well developed vascular apparatus ; tra- 

 cheae, or pulmonary sacs for breathing air ; they have four pairs 

 of articulated extremities, but are always destitute of wings. The 

 head is confounded with the thorax : 



15. That animals of the class CRUSTA'CEA have white blood ; 

 a circulatory apparatus ; articulated extremities ; five or seven 

 pairs of legs, and branchiae for breathing water ; 



16. That animals of the class CIRR'HOPODA have white blood, 

 but no extremities for locomotion ; and they always live attached 

 to other bodies. They breathe water by means of branchiae : 

 and, last, 



17. That animals of the class ANNE'LIDA have coloured blood ; 

 are unprovided with articulated extremities; and, in general, have 

 branchiae for breathing water. 



CLASS OF INSECTS. 



18. The class of insects includes all articulated animals that 

 are unprovided with a circulatory apparatus properly so called, 

 that breathe by tracheae, undergo, in general, a metamorphosis 

 while young, and possess six articulated extremities ; they gene- 

 rally have wings, and the head, which is furnished with antennae, 

 is always distinct from the thorax. 



12. What are the distinguishing characters of insects. 



13. How are myri'apods characterized? How are they distinguished 

 from insects. 



14. What are the characters of arach'nidans ? What distinguishes them 

 from insects? 



15. How are crusta'eeans distinguished? How do they differ from 

 cirr'hopods ? 



16. What are the characters of cirr'hopods? What distinguishes them 

 from insects ? 



17. What are the characters of anne'lidans ? How are they distinguished 

 from myri'apods ? 



18. What are the general characters of animals composing the class of 

 insects ? 



2 



