ANATOMY OF THE BEE. 21 



35. Wings The wings (Fig. 6), which also originate in the 



thorax, are four in number, — the anterior pair and the pos- 

 terior pair, articulated into the meso-thorax and the meta- 

 thorax respectively. The upper and outward margin of the 

 posterior wing has a number of booklets (B. e, f,) and the lower 

 ahd inner margin of the anterior wing is folded in a plait (A. 

 c, d.). As the anterior wing is raised for flight, its folded 

 plait passes over the booklets of the posterior wing and is 

 caught by them (C, and D. p, h), so that the two wings act 

 together as one wing, thus, on the principle — " Unity is 

 strength," adding power and speed to the flight. When the 

 bee alights, the wings become free, and lie closely over the 

 abdomen, thus permitting the insect to enter comb cells, which, 

 otherwise, would be impracticable. The wings of the drone 

 are the largest, and those of the workers the shortest. The 

 vibrations, when in flight, have been calculated by Marey at 

 igo per second, and by Landois at 440. Bees can fly back- 

 wards, and. even when in full flight, can stop very suddenl). 

 When leaving the hive to collect food they will fly at the 

 rate of from fifteen to twenty miles an hour ; but, when return- 

 ing heavily laden, their speed is much less, varying from five 

 to twelve miles an hour. The limit of their usual flight from 

 the hive on foraging duty may be taken as two miles. They 

 have, however, been known, in exceptional circumstances, to 

 travel as far as seven miles in search of food. 



36. Spiracles and Tracheaa The breathing of the bee is 



carried on through the spiracles, or openings, in the sides of 

 the body (Fig. 7. s) which can be opened or closed at will. 

 These spiracles admit air to the tracheae, or tubes, which, as 

 shown in the illustration, ramifying in countless number 

 throughout the body, convey the necessary oxygen to the 

 various organs. The development of the tracheas into vesicles, 

 or air sacs, of which the main ones lie in. the anterior portion of 

 the abdomen in the worker and drone, greatly assists the bee's 

 flight. When inflated, the air sacs increase the size of the 

 body, thus altering its specific gravity and reducing the amount 

 of effort necessary to accomplish a long and rapid flight (21). 

 A bee, at rest, suddenly disturbed, may often be observed to 

 jump, or fly a couple of inches before taking wing, the air sacs 

 not being filled ; then, with the lifting of the wings, and rapid 

 extension and contraction of the abdomen, air is drawn through 

 the spiracles into the vesicles ; the spiracles are closed, and the 

 insect rises in flight. Immersed in liquid, breathing through 

 the spiracles is stopped, and the insect dies. 



