At a place 9/10 mile east and 8/10 mile north of Barrow Village (June 23, 1952) a tenth nest, containing five fresh eggs, was noted in a lemming runway that had been enlarged from a soil fracture. The top of the nest was flush with the surface of the ground and there was no overhead protection. This nest had the least nesting material of any nest of this species examined to date; there was no nesting material of any kind on the sides adjoining the walls of the fracture. At Umiat (June 26, 1952) an eleventh nest, containing six eggs, was so placed that its top was flush with the surface of a raised polygon, and closely resembled those at Point Barrow except that the cup was lined with brown and white feathers of the willow ptarmigan. Additional data are as follows: weight of entire nest, 20 grams; weight of inner cup, 7 grams; diameter of cup, 65 mm; depth of cup, 30 mm; width of entire nest, 100 mm. As was usual with other nests of this species, the outer edge of one side was covered with moss. In the period July 13-August 15, from several localities on the Arctic Slope, Lapland longspurs were caught in traps (20 feet apart) set in linear lines among sedges. The average distance between traps catching longspurs was 1400 feet. Other Lapland longspurs observed in the same period at these same localities averaged one per 400 feet of walking on my part. The greatest number of longspurs trapped was at Kaolak on July 24, 1951; 100 traps yielded 6 longspurs. The greatest number observed--one per 100 feet--was at Topagaruk on July 5, 1951. Although the longspur on the Arctic Slope is the most common bird, it is absent from some areas there. On each of two trips (July 29-30) across one mile of upland plateau between Barrier Lake and Teshekpuk Lake, we did not see longspurs. This plateau is a travel lane maintained by caribou. Juveniles were first trapped on July 5, 1951, at Topagaruk; others were observed on this date but they could not fly. The first juvenile noted in flight was on July 9, also at Topagaruk. The increase of juveniles there caused the longspur to be the most common bird in the field (50 per cent in abundance). On July 15 at Kaolak River, most of the longspurs noted were juveniles, but they were able to fly well. The adult males and females, which were molting at this time, were more secretive in their movements than longspurs at Topagaruk on July 5. Adult males were molting as early as July 2 at Kaolak. On July 25 at Kaolak longspurs were mainly in groups of five or six; others were in groups of 18 or more. As late as August 21 (Gavia Lake) longspurs were still in family groups or occurred as singles.