One cork door measuring 1 line across contained 1 layer of silk. Four " doors " 1-1/2 lines " 3 layers " One " door " 1-1/2 " 2 " One " door " 1-3/4 " 4 " One " door " 2 " 5 " Two " doors " 2-1/2 " 6 " One " door " 2-1/2 " 5 " One " door " 3 " 8 " Two " doors " 3-1/2 " 5 " One " door " 3-1/2 " 7 " One " door " 4 " 7 " Two " doors " 4-1/2 " 8 " One " door " 4-1/2 " 7 " Two " doors " 5 " 9 " One " door " 5 " 5 " One " door " 5 " 6 " One " door " 5 " 13 " One " door " 5-1/2 " 9 " One " door " 5-1/2 " 10 " One " door " 5-1/2 " 14 " One " door " 6 " 12 " The apparent exceptions to this rule, in which the larger doors have fewer layers than some of the smaller ones, may probably be accounted for in the following manner. During the heavy rains and in times of drought flakes of earth often become detached from the sloping banks, and carry away the doors of such nests as are found in them. This happens frequently, and the spiders hasten to repair the damage and spin new doors. But I have found, on examining eight of these new doors, that, even in large nests,[107] they do not then contain more than three layers of silk; so that each time a nest of any size loses its door, the number of layers is greatly reduced. [Footnote 107: Of the eight doors in question the smallest measured 3-1/2 lines across, and the largest 7 lines.] In the case of six of these nests I had myself acted the part of the landslip and removed the existing door. These original and apparently undisturbed doors measured 3-1/2, 4, 5, 5, 5, and 5 lines across, and contained respectively 5, 7, 8, 13, 9 and 5 layers of silk; while of the equally large doors which replaced them five contained three layers of silk only, and the remaining nest but a single layer. INDEX. PART I.--HARVESTING ANTS. Ælian on harvesting ants, 7-9. Aldrovandus, radicle of seed gnawed by ants, 9. Algiers, harvesters observed in, 52. Aphides and cocci not sought by harvesting ants, 48.