For example, the foreleg of the mole is admirably suited for digging underground. A similar modification is found in an entirely different group of the animal kingdom, namely, in the mole cricket[…] In both of these cases the adaptation is the more obvious, because, while the leg of the mole is formed on the same general plan as that of other vertebrates, and the leg of the mole cricket has the same fundamental structure as that of other insects, yet in both cases the details of structure and the general proportions have been so altered, that the leg is fitted for entirely different purposes from that to which the legs of other vertebrates and of other insects are put.
Source: wiktionary