//"it /.\ ?Et rs brea mi-: 



19 



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strengthened bv hollow rods called " \ ' their branches 



being 1 1 1 « - " venu There an- in the wrings of n 



six main u .6., tin- ■ 'In- sub 



median, mbmedian, internal, and anal. They 

 arc hollow and usually contain an air-tube, 

 ami a nerve often accompanies the trachea in ^y 

 the principal veins. The arterial blood from 

 the heari (as seen in the cockroach by Mose- 

 1«'\ ) flows directly into the costal, subcostal, 

 median, and Bubmedian veins; here it is in 

 part aerated, and returns to the heart from 

 the hinder edge of the wings through the 

 hinder Bmaller branches and the main trunks 

 of the internal and anal veins. So that the 

 wings of ii ct as lungs a- well a- organs 



.>!' flight. For the latter purpose, the prin- 

 cipal veins are ,-ituated near the front • 

 of the wing, called the costa, and thus the 

 wing is strengthened where the most -train 

 comes during the beating of the an- in flight. 



The win-- of an insect in making the strokes during flight 

 ribes .i figure 8 in the air. A fly's wing ma 

 revolutions in a second, executing therefore • mple 



•illations. 



How Insects Breathe. — [nsects breathe by means of a 

 complicated Bystem of air-tubes ramifying throughout the 

 body, the air entering through a row of spiracles, or breath- 

 ing-holes {stigmata), in the sides of the body. There are 

 in locusts two pairs of thoracic and eight pairs of abdominal 

 spiracles. The first thoracic pair (Fig. 2) - - I tated on 

 the membrane connecting the prothorax and mesothorax, 

 and is covered by the hinder edge of the pronotum (usually 

 called prothorax). The second spiracle I on the 



posterior edge of the mesothorax. Therea I abdominal 



spiracles, the first one situated just in from 

 sac or tympanum, and the remaining seven are small open- 

 's along the side of the abdomen (Fig. - , From I 



YO— 





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iber. 



