CLASSIFICATION 



branous, minutely reticulate, with characteristic costal joint (nodus), 

 arculus and triangle. Abdomen slender, with ten segments. Cerci 

 one-segmented. Nymphs aquatic; adults predatory. Dragon-flies 



FIG. 23. Benacus griseus. Slightly reduced. 



FIG. 24. Head louse, 

 Pediculus capitis, female. 

 Length, 2 mm. 



and damsel -flies. Example, Libellula (Fig. 21). About two thousand 

 species have been described. 



FIG. 25. Hydrophilus triangularis. Natural size. 



9. Thysanoptera. Metamorphosis direct, but including a subpupal 

 stage. Eyes well developed. Mouth parts suctorial, in part asym- 

 metrical. Prothorax long, free. Tarsus one- or two-segmented, ter- 



