78 



THB beb-kbbpbr's guide ; 



long distances. This disproves the general view that insects 

 can see but at very short range. 



Within the head is the large brain (Fig. 27, b), which will be 

 described as we come to speak of the nervous system. There 

 are also chitinous bars (Fig. 14) and braces within, which serve 

 greatly to strengthen this portion of the insect. 



APPBNDAGBS OF THE THORAX. 



The organs of flight are the most noticeable appendages 

 of the thorax. The wings are usually four, though the Diptera 

 have but two, and some insects — as the worker-ants — have 

 none. The front or primary wings (Fig. 2) are usually larger 

 than the secondary or hind wings, and thus the mesothoracic 



Fig. 25. 



L Muscles to raise front wing 

 A Muscles of hind wing. 



Musckn of Thorax, after Wolff. 



D Muscles to lower front wing. 



or middle ring of the thorax, to which they are attached, is 

 usually larger than the metathorax or third ring. The wings 

 consist of a broad frame-work of veins (Fig. 2), covered by a 

 thin, tough membrane. The main ribs or veins are variable 

 in number, while towards the extremity of the wing are more 

 or less cross-veins, dividing this portion of the wings into more 

 or less cells. In the higher groups these cells are few, and 

 quite important in classifying. Especially useful in group- 

 ing bees into their families and genera are the cells in the 



