In southwest Montana, near the town of Three Forks, Milligan Creek cuts a small and seemingly mundane notch through dry limestone hills. Milligan Creek is unassuming and small enough to be effortlessly stepped over in most places. In fact, it flows underground for much of its 4-5 mile journey to the Jefferson River. Incredibly, forty-nine species of long-legged flies (Dolichopodidae) - fully 61% of the 81 species recorded to occur in Montana (Pollet et al. 2004) - have been collected along a very short stretch of this creek (see list below). These species were found during eight short trips to Milligan Creek since 2001, using only nets, and along about a 200 meter length of the creek (about 1,000 square meters in area). Species were found where Milligan Creek Road crossed the creek near a large limestone cliff (with nesting cliff sparrows) with a small pool of water at base (Figure 1; N45º53.26’, W111º40.72’; 1300 m elevation). Milligan Creek has yielded seven apparently undescribed dolichopodid species (including Telmaturgus robinsoni; Runyon 2012), the only known occurrence of the genus Micromorphus in Montana, and state records for several species.