Dragonfly Nymphs 



209 



Dragonfly nymphs have their gills developed upon 

 the inner walls of a rectal respiratory chamber, and not 

 visible externally. Hence, the abdomen is much wider 

 than in the damselflies. Water drawn slowly into the 

 gill chamber through an anal orifice, that is guarded by 

 elaborate strainers, may be suddenly expelled by the 

 strong contraction of the abdominal muscles. Thus 

 this breathing apparatus, also, is used to aid in locomo- 

 tion. The body is driven forward by the expulsion of 

 the water backward. 



Damselfly nymphs live for the most part clambering 

 about among submerged plants in still w^aters; a few 



Fig. 116. The burrowing nymph of a Gomphine dragonfly, 

 with an elongate terminal segment for reaching up 

 through the bottom mud to the water. 



cling to plants in the edges of the current, and a very 

 few cling to rocks in flowing water. Dragonfly nymphs 

 are more diversified in their habits. Many of them 

 also clamber among plants, but more of them sprawl 

 in the mud of the bottom, where they lie in ambush to 

 await their prey. One considerable group (the Gom- 

 phines) is finely adapted for burrowing in the silt and 

 sand of the bottom. 



All are very voracious, eating living prey in great 

 variety. All appear to prefer the largest game they 

 are able to overpower. Many species are arrant canni- 

 bals, eating their own kind even when not starved to it. 

 As a group they are among the most important carni- 

 vores in shoal fresh waters. 



