During the 1936 occurrence of Brood X of Magicicada septendecim in Maryland, various misunderstood phases of emergence and behavior were investigated. The insect remained in its soil burrow about 3 wks. before emergence and during this period no feeding was discovered. Actual emergence from soil burrows and turrets was observed repeatedly. Normal ecdysis took place only on objects to which the insect could cling securely. Controlled shelters showed that temps. above normal accelerate development during the month prior to emergence and that excessive temps. cause many full grown nymphs to become deformed during the final transformation. The various theories as to turret formation were all rejected on the basis of various experiments and observations. Eggs laid in twigs that died later appeared to hatch only in rare cases. Nymphs were observed hatching and dropping to the soil, where they burrowed beneath the surface. Nymphs do not require cracks or holes for their entrance if the ground is soft. A new fungus enemy of the nymph, Metarrhizium anisopliae, was found. The population of cicadas in the soil in 2 apple orchards was computed to be 1,403,920 per acre.