INSECT VARIETY. 2U7 



CHAPTER V. 



WING BEATING AND VOCAL MUSIC CONSIDEEED AS A MATERIAL AGENT 

 IN REPRODUCTION AND DISTRIBUTION. 



" to watch the grape of Lemnos 

 Swelling out its purple skin, 

 When the merry little chirpings 



Of the Tettiges begin ! 

 For the Lemnian ripens early, 



And I watch the juicy fig, 

 Till at last I pick and eat it, 

 When it hangeth soft and big." 



Aristophanes [Trans.). 



A LITTLE familiarity with the dissection o£ insects serves to 

 show us that their system of respiration^ as compared with the 

 typical organs of the vertebrate animals, may be denominated 

 complex. To examine this mechanism, the subject larva or 

 perfect insect may be either killed, cut open longitudinally, and 

 then placed beneath a vessel of water, or, after being prepared, it 

 may be allowed to dry pinned out on a flat board. Then by 

 manipulating with a needle-point, we may learn that the air- 

 pipes or tracheae, composed of a spiral elastic thread lined by a 

 silvery membrane, pass in two main-tubes along either side of 

 the body (Plate IL, Fig. 1, t), and at each segment or division 

 communicate with one of an external row of breathing-slits or 

 spiracles (Plate II., Fig. 3) . From the same points they send out a 

 series of branches that replenish the internal air-bladders insects 

 possess in common with all flying and swimming life (Plate II., 

 Fig. 1, /', t' , t' . . . ), or disperse in the muscular valves of the 

 circulating vessels, and penetrate the ovaries, legs, and all parts 

 of the organisation. To the anterior rings of the body the ex- 

 ternal breathing-pores are often wanting, and here in lieu, offsets 

 of the tracheae ramify in the antennae, or wings ; the latter perform 



