The web construction behavior of Achaearanea tesselata (Keyserling 1884) was observed in the field and in captivity using suspended wire frames that allowed detailed observations. Construction included three stages: preliminary exploration during which lines were broken, reeled up, and replaced; construction of anchor lines and the upper tangle; and construction and then filling in of the sheet below the tangle. Repeated visits to the mouth of the retreat during tangle construction resulted in the apparent reinforcement of the few lines radiating from this area, a possible adaptation to sense the location of prey in the web, and to facilitate orientation of the spider to prey in the web. Filling in the sheet, which alternated with additions to the tangle, included two previously undescribed behavioral patterns: irregular wandering on the sheet and apparent attachments of the dragline using only the two legs IV to hold previous lines against the spinnerets. The spider needed 1–2 nights, working several hours each night, to make a complete tangle and sheet and added lines and extended both the tangle and the sheet on subsequent nights. Spiders adapted the shapes of their webs to their surroundings.