SEM images of the three layers of A. atlas cocoons are shown in Figure 2. As seen from the figure, the outer layer (Figure 2a) has a relatively open construction com- pared to the intermediate (Figure 2b) and inner layers (Figure 2c). The inner layer is very compact and has fi- bers much closer to each other than the fibers in the outer and intermediate layers as seen from Figure 2c. As seen from Figs. 2a to c, the A. atlas caterpillar extrudes two adjacent fibers simultaneously. The two adjacent fi- bers are attached to each other by glues in the interme- diate and inner layers but the outer layer has fibers that are not as extensively attached to each other as fibers in the other two layers. Inner layer also had fibers with slightly lower diameters than the fibers in the outer and intermediate layers. Average diameter of a single fiber in the inner layer was 17 ± 5 μm and those in the outer and intermediate layer was 19 ± 4 and 20 ± 4 μm, respec- tively. It has been reported that the filaments in A. at- las consist of microfibrils of about 1 μm in diameter and embedded in a soft matrix [26].