The mechanism for controlling hatching from egg masses has received little attention in insects. In this study, both the pattern of hatching and factors influencing hatching were examined for the egg mass of the migratory locust, Locusta migratoria, under continuous illumination at 30°C. The eggs hatched simultaneously from the egg pods with a mean hatching period of 2.4 h. When the eggs were kept in different-sized masses, they tended to hatch earlier and across a shorter period as the mass size increased. However, the eggs in each mass hatched in synchrony, irrespective of the mass size. The eggs separated from the pods, and kept singly in moist sand, hatched later and across a longer period than those kept in the pods. Egg separation performed at various times revealed that hatching time and synchrony were determined on the day prior to hatching. The same conclusion was drawn when the eggs separated on day 10 were grouped as either egg masses or pairs at various times before hatching. Two eggs from different pods, incubated in physical contact with each other, hatched in synchrony if they were similar ages. In this case, the hatching was advanced or delayed depending on whether eggs were paired with older or younger counterparts. These results suggest that the L. migratoria eggs adjust the timing of hatching based on the information obtained from neighboring eggs, although the actual stimuli involved remain unknown.