Field work in Entomology is full of delightful opportunities, and none, just at present, is more inviting, none more certain to repay well even a little effort, none more sure to yield discoveries of scientific value, than work upon the life-histories of Dragonflies.Of the species occurring throughout the central tier of States, a majority perhaps has now been bred; but of the Canadian, far western and southern species the known nymphs are few and far between.