VII. ARTHROPODA, SUMMARY OF IMPORTANT FACTS 437 



38. The ]\IALACOPODA are intermediate between Annelida and Insecta. 

 They have indistinctly segmented bodies with parapodia-like feet, 

 segmental organs, and tracheae. 



39. The INSECTA breathe by trachea.-; the head bears four pairs of 

 appendages: antennae, mandibles, maxilke, labium; since tracheae are 

 present the circulatory system is reduced; the reproductive organs open 

 at the hind end of the body. 



40. The Insecta are divided into Chilopoda and Hexapoda. 



41. The C/iilopoda have numerous body segments with a pair of legs 

 on each; behind the head are a pair of poison feet. 



42. The Hexapoda .have the body divided into head, thorax, and 

 abdomen. 



43. The abdomen consists of a varying number of somites and lacks 

 evident appendages. 



44. The thorax consists of three segments, pro-, meso-, and metathorax, 

 each bearing a pair of legs, and meso- and metathorax usually a pair of 

 wings each. 



45. The head bears, besides the mouth parts and antennae, an un- 

 paired upper lip (labrum) ; two compound eyes, and usually one to 

 three ocelli. 



46. The structure of the mouth parts varies with the food; they are 

 either biting, licking and sucking, or piercing in function. 



47. Wingless insects usually have a direct (ametabolous) develop- 

 ment with numerous ecdyses. 



48. Winged insects (and many without wings have descended from 

 winged forms) have a metamorphosis in which the larva differs more or 

 less from the imago (metabolous insects) ; the larva never has wings. 



49. An incomplete metamorphosis (hemimetabolous development) 

 occurs when the larva with each molt becomes more like the adult, the 

 wing pads becoming larger with each ecdysis. 



50. In complete metamorphosis (holometabolous development) 

 the changes occur in the last molting stage, which is a stage of rest, the 

 pupa. 



51. Classification of Hexapoda is based upon structure of mouth 

 parts and wings as well as upon regional relations and development. 



52. The Apterygota are wingless, ametabolous Hexapoda with biting 

 mouth parts. 



53. The Archiptera have biting mouth parts with incompletely fused 

 labium, net-veined wings, and incomplete metamorphosis. 



54. The Orthoptera resemble the Archiptera in mouth parts and devel- 

 opment, but have parchment-like wings. 



