Wiktionary
arachnomancy
n. 1 The study of the appearance and behavior of spiders, or the patterns of their webs (possibly related to the third meaning) for use in divination. 2 The ability to take control over spiders with the intent to use them for attacking purposes or similar purposes. 3 Also the divination of patterns, for example in geometric patterns, and tapestries. 4 Possibly also the creation of a view using scientific results by separating, and combining of new research.