Ontogenetic shifts in activity and habitat use by the scorpion Centruroides vittatus in Laredo, Texas can occur with shifts in microhabitat use, the height of the scorpion in vegetation and seasonal and lunar activity among different sizes of C. vittatus but not taxa of prey in the diet. The microhabitat use by the different size classes was significantly different with significant associations among the cacti with a high frequency of larger scorpions on prickly pear cactus and strawberry cactus and between grass and other vegetation with a high frequency of smaller scorpions on grass. A comparison of the mean height of scorpion on blackbrush among the size classes was not significant but height on grass was significant. The activity of the size classes was significantly different among months and lunar cycle. Temperature had a significant effect on the activity of scorpions by different size classes and in different microhabitats. Caterpillar availability did not have a significant association with either scorpion size class or microhabitat use by scorpions. The taxa of prey captured by the different size classes were not significantly different including no notable difference in scorpions feeding on caterpillars. The size classes of C. vittatus show microhabitat and temporal shifts in activity. The results suggest that smaller scorpions can possibly be avoiding the larger scorpions by reducing activity in the preferred microhabitat (prickly pear and strawberry cactus) of larger scorpions.