4. Results
4.1. Morphology of the cocoons
A summary of cocoon morphology for the 27 species is shown in Fig. 2. Cocoon morphologies are plotted on the phylogenetic tree, which describes evolutionary relationships among various silkworm species based on their genetic characteristic [25], [26] and [27]. Each node in a rooted phylogenetic tree represents the deduced most recent common biological ancestor of the descendants. SEM pictures of both outer and inner surfaces of cocoons are shown to make a comparison on their distinctively different morphologies. The cocoon features, e.g. open or closed structure, degree of nonwoven structure, numbers of layer connectivity and extra components such as calcium oxalates are indicated in the pictures in Fig. 2. The structural and morphological type of cocoons employed is usually constant with a genus. For example, six Antheraea cocoons all have closed cocoons, nonwoven structures and calcium oxalates crystals, and both Caligula simla and Argema mimosae cocoons have closed cocoons, lattice structures, single layer and no calcium oxalate crystals.