PLATE XX. 



Fig 1. Ventral view of terminal abdominal segments of male No- 

 tonecta undulata Say. 



.Fig. 2. Fifth instar nymph. 



Fig. 3. Ventral view of terminal abdominal segments of female. 



Figs. 4a to 4e. Diagrams of dorsal view of meso- and metathorax of 

 nymphs, first to fifth instars, respectively, showing the developing wing- 

 pads. 



Fig. 5. Third instar nymph. Both rows of swimming hairs shown. 



Fig. 6. Antennae of fifth instar nymph. 



Fig. 7. Antennae of adult male. 



Fig. 8. Second instar feeding upon an ostracod. 



Fig, 9. First instar nymph, drawn by Miss Ellen Edmonson. 



Fig. 10. Tarsus of hind leg of first instar nymph, showing the tarsal 

 claws, which become less conspicuous as development advances. 



Fig. 11. Egg of Notonecta undulata, showing details of structure, 

 drawn by Miss Ellen Edmonson. Plate first used in Ento. News, XXVIII. 



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