Complex sentence: In late summer and fall, the adult female girdles small branches (1/4 to 1/2 inch diameter) with its mandibles, cutting through the bark and into the wood, resulting in an effect that looks almost as if it were cut with a small saw.
Split into simpler sentences: In late summer and fall, the adult female girdles small branches, diameter, with its mandibles, cutting through the bark and into the wood. The resulting effect looks almost as if it were cut with a small saw.