MANUAL OP THE APIARY. 55 



colors to their hives. Apiarists have frequently noted that 

 bees have a rare faculty of marking positions, but, for slight 

 distances, their sense of color will correct mistakes which 

 would occur if position alone was guide. 



APPENDAGES 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. 3, A) are usually 

 larger than the secondary or hind wings (Fig. 3, £), and thus 

 the mesathoracic or middle ring of the thorax, to which they 

 are attached, is usually larger than the mettathorax or third 

 ring. The wings consist of a broad frame-work of veins 

 (Fig. 3), 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. Es- 

 pecially useful are the cells in the second row, from the frontal 

 or costal edge of the front wings, called the sub-costal cells. 

 Thus in the genus Apis there are three such cells (Fig. 3, A, 

 1, 2, 3), while in the Melipona there are only two. The ribs 



Fig. 7. 



Thorax of Bee magnijied three times. 



a, a, a— Muscles. b, 5— Crust. 



or veins consist of a tube within a tube. The inner one 

 forming an air tube, the outer one carrying blood. On the 

 costal edge of the secondary wings we often find hooks, to 

 attach it to the front wings (Fig. 3, £, a). 



The wings are moved by powerful muscles, compactly loca- 

 ted in the thorax (Fig. 7, a, a, a), whose strength, as well as the 

 rapidity of the vibrations of the wings when flight is rapid, 



