Who could imagine that just because the lady mosquitos, tiring of their usual meal of ripe bananas and plant juices, acquired the habit of sucking blood, vast regions would be devastated and beings millions of times their size would die by thousands. And this, too, not through any real fault of the tiny creatures themselves, but just because some of the persons whose blood they sucked had microscopic wiggling things living in their blood corpuscles, which crawled into the soft throat glands of the mosquito and waited there for a chance to get out into the blood channels of some other human beings. When one pictures the grief of desolated homes, death-bed agonies of tossing fever patients, the quarantined vessels at anchor in tropical harbors, yellow flagged, with crews dead or dying, the streets of deserted houses from which all life has gone forever through yellow fever and malaria, there is something ghastly in the picture of the winged lady mosquitos flitting airily from pale-faced patients to ruddy-cheeked happy people, unwitting carriers of death. No conquest of science seems more wonderful in its simplicity and more remarkable in its importance than the discovery that the glands at the base of the mosquito's bill can become diseased and harbor a microscopic parasite, and transform this merely buzzing, annoying insect into one of the most dangerous creatures alive. To Dr. L. O. Howard, the pioneer of economic entomology, is due the great credit for first showing how this creature can be killed by the use of kerosene on the stagnant waters where the females lay their eggs. [Illustration] ONE OF THE BEE FLIES (_Sparnopolius fulvus_, Wied.) No butterfly or any other creature of the air could be more beautiful than this dream of early summer. The black velvet body, into which the sunlight sank and disappeared, the fringe of golden hairs along its sides, the steel gray, myriad-facet eyes of which its head was made, and the delicately formed wings, so thin that the light in passing through them was refracted into rainbow tints, made it seem to me more beautiful than almost any of those gorgeous forms of insect life which sometimes fill the clearings in Brazilian forests. It does seem strange that such a thing as this should live its other life a parasitic grub within the larva of some caterpillar, or in the egg-case of some grasshopper; but so it seems to do. It spends its childhood as a disease, and its mating days as a dainty fly among the nectar-bearing flowers. [Illustration] ANOTHER OF THE BEE FLIES (_Spogostylum simson_, Fab.) Where you see the carpenter bee you always see these bee flies waiting for the bee to go away from home. When the mother bee is out the female fly goes into the cell of the bee and lays her egg, and when her larva hatches out it eats up the bee's larva. [Illustration] LARGE SYRPHID FLY (_Melesia virginiensis_, Dru.)