Three mantid species, Tenodera aridifolia (Stoll), Hierodura patellifera (Serville), and Statilia maculata Thunberg, of varying body size and habitats, exhibited defensive reactions when faced with a natural enemy, the Japanese skink, Takydromus tachydromoides (Schlegel). Defensive reactions were analyzed as primary or secondary defenses for all stages. Of the primary defenses, the cryptic reaction was the main defensive reaction: mantids lowered the prothorax and simultaneously stretched the prothoracic legs, the antennae were arranged forward, and the abdomen was sometimes extended posteriorly. The frequency of the subcryptic reaction as a primary defense tended to increase with more advanced developmental stage. The primary defensive strategy switched at specific developmental stage and also depended on the distance between the prey mantid and the natural enemy. In some instars, T. aridifolia and H. patellifera displayed the cryptic reaction when the mantid—foe distance was long, whereas they displayed the subcryptic reaction when the mantid—foe distance was short. However, S. maculata did not switch defense strategies based on the mantid—foe distance. The secondary defenses of young instar nymphs of T. aridifolia and H. patellifera were primarily defensive reactions, whereas the frequency of aggressive reactions tended to increase with developmental stage. S. maculata did not display aggressive reactions during any stage. We concluded that the primary and secondary defenses used by mantids depend on the developmental stage and mantid—foe distance. Moreover, three mantid species that vary in both body size and habitat showed different defensive reactions when faced with a natural enemy.