The little wren-like birds of this genus (_Scytalopus_), known commonly as “tapacolas,” are perhaps among the most difficult to collect of any species in South America, and for this reason they are invariably only poorly represented in museum collections. Native collectors, hunting mainly with blow-guns, have gathered many thousands of birds, the greater number of which have eventually found their way to millinery establishments and scientific institutions in many parts of the world; but usually only those of brilliant plumage, and others which could be taken with little difficulty, have been collected. The small, slate-colored or blackish tapacolas, found only in the densest of subtropical forests or among the tangled vegetation bordering bleak, frigid _paramos_, have usually been overlooked. This is not surprising when we find how seldom even the trained field-naturalist of to-day finds it possible to lure the tiny, feathered creature from its secure retreat among the mosses, roots, and ferns to which its mouse-like habits confine it, and how rarely he succeeds in recovering the inconspicuously colored bird after it has been shot. Even after a long, patient search has revealed the specimen lodged somewhere in the deep stratum of matted plants, it is by no means sure of reaching the museum; I know of instances where birds, slipping from the hunter’s hands and dropping at his feet, have been forever lost in the riot of vegetation which everywhere carpets the ground. Our quest for this little creature was destined to extend over a period of months, and to take us into many an out-of-the-way place. We were eager to begin the search, so took the first available train which left La Quiaca two days after our arrival and started southward.