Periodical cicadas (Magicicada spp.) are insects with a 13- or 17-yr life cycle that spend most of this time underground feeding on xylem from plant roots. In the 13th or 17th year of the life cycle, typically millions of cicadas emerge from the soil within a given area in near perfect synchrony. Factors controlling emergence, whether exogenous or endogenous, remain a mystery. By removing 13-yr periodical cicadas [Magicicada cassini (Fisher 1851)] from their natural environment in northwest Arkansas and controlling most exogenous factors in the laboratory, this study examined deviations or similarities in life cycle patterns compared with those occurring in nature. In a series of replicated experiments starting 9 mo before natural emergence in environmental chambers with constant light and temperature, we found that 14 of 60 nymphs associated with soybean (Glycine max L.) plants or cedar trees (Juniperus virginiana L.) successfully emerged in May 1998 in synchrony with the natural population from which they were removed. Seven of 10 nymphs feeding on a control cedar tree for 9 mo at the field study site also emerged in May 1998. It seemed that all nymphs surviving 9 mo under laboratory conditions emerged during the period of natural emergence. Whether this represents endogenous control of emergence remains to be critically tested, but from data collected in this study, the internal timing of emergence seems to be set at least 9 mo before emergence.