44 



The Living Things of the Earth unit i 



Fig. 55 (left) Have you ever 

 seen the tongue of a housefly 

 inovhig up and down as it 

 lapped its food? (American 



MUSEUM OF NATURAL HIS- 

 TORY) 



Fig. 56 (below) The Hes- 

 sian fly ijipires wheat. Its lar- 

 vae Slick the sap from tender 

 parts of the stem. Can you 

 find the halters that take the 

 place of the second pair of 



Labium 

 (outer lip) 



Skin surface 



Proboscis 



(piercing mouth parts) 



Fig. 57 (left) The mosquito keeps its piercing 

 moutl? parts in a sheath when not in use. The 

 mouth parts forni a tube through which blood 

 is pumped from the victim. (American museum 



OF NATURAL HISTORY) 



another difference: moths spread their 

 wings flat when resting; butterflies hold 

 thcni upright. 



The two-winged insects — flies. The 

 members of this group have onlv one 

 pair of wings. There are stumps in 



