IX 



DRAGON-FLIES 



337 



tracheal gills. Advanced larvae are able to use their 

 spiracles, and when placed in boiled water, creep up 

 the stick head foremost, throwing the body into a 

 horizontal position when the surface is reached, so as 

 to expose the spiracles to the air. 



Fig. 99. — Part of respiratory organ in rectum of /Eschna larva. One of the six 

 muscular bands occupies the middle of the figure. The ventral tracheal trunk 

 is seen giving off branches to the wall of the rectum. Another trunk, more 

 dorsally placed, is shaded. A third, which runs above the rectum, is omitted. 



From all these observations it is clear that the 

 larvse of Dragon-flies, especially in their later stages, 

 fill their tracheal tubes directly from the atmosphere 

 to a much greater extent than had been previously 

 supposed. 



z 



