Notwithstanding much that has been learnedly written upon the family Bombycidæ, or Spinner Moths, no strong exclusive structural characters have been brought to light which hold the groups together as a natural family. Following Linné and Latreille, the American authors, Dr. Harris and Dr. Packard, have, however, considered such a family to exist. In Germany the different groups, or sub-families, have been raised to the rank of families, while under the loose term Bombyces the Spinner Moths as a whole have been designated.