The lactate dehydrogenase activity was examined in skeletal muscles of specimens of 53 species of Orthoptera belonging to five families of Ensifera and four of Caelifera. The results showed that: (1) the five families of Ensifera contain a low level of lactate dehydrogenase activity in their jumping muscles, whereas two families of Caelifera, Catantopidae and Acrididae, contain a far higher level; (2) in the four families of Caelifera, there are two well‐distinct levels of activity of lactate dehydrogenase in leg muscles, and (3) the lactate dehydrogenase activity in the jumping femurs is, in general, more than double that of the non‐jumping femurs. It was suggested that this difference in activity between specialized and non‐specialized leg segments represents a metabolic adaptation to burst muscular activity.