74 FOURTH ANNUAL REPORT OF 



perietice as is yet unrecorded, and to sift from the mass of unimportant, 

 facts, the more salient and valuable ones. 



Of the eight species which will be treated of, four, namel}-, mori, cyntliia, 

 yama-mai, and Pernyi, are of foreign origin, and the other four, namely. 

 Gecropia, Promethea, Luna, and Polyphemus, are native. I shall give an ac- 

 count of the changes these different worms undergo, because these changes 

 have not before received sufficient attention. It will be noticed that, when 

 newly hatched, all of them, even to the mulberry species, are, in form and 

 structure, exactly alike ; and that they differentiate moi'C and more as they 

 increase in size, until each acquires its specific characters. This is in accord- 

 ance with a law which has only latel}' been fully appreciated, and which 

 prevails throughout nature; namely, that in the early stages, the species of 

 a genus or of a Family closely resemble each other, no matter how diss^mii- 

 lar they afterwards become. To the Darwinian such facts are significant, as- 

 implying descent from a common ancestr3^ 



All these silkworms cast their skin four times during the feeding period,, 

 and thus have five different stages of growth; the worm resting and fasting 

 from one to three days, then gradually working off the old skin, and after- 

 wards knocking off the head. 



The males of all genei-ally issue from the cocoons before the females.. 

 This is no doubt due to the fact that the females are generally the largest^ 

 have the most vitality, and consequently require a greater time to feed^ 

 and to assimilate the food ; for it has often been noticed that a snuill female 

 will develop faster and consequently issue sooner than a large male. 



The males generall}- have much broader antennie than the females ; but 

 in Promethea the difference is not great, and in cynthia it is often impercep- 

 tible. 



They all, when in the cocoon, are furnished with an acrid or Boml»yci& 

 fluid, with which they weaken the resisting force of their cocoons, and facil- 

 itate the exit of the moth ; though those which make rounded or closed co- 

 coons are much more amply supplied ihan those which form pointed or 

 open ones. 



All the cocoons, whether pointed or rounded, are spun in one continu- 

 ous thread. In issuing, the moths of all of them rupture, more or less, the 

 threads of the cocoon, thus rendering it valueless for reeling. Many writ- 

 ers assert to the contrary ; but I have examined no deserted cocoon which 

 has not shown some broken threads, and have witnessed the threads break 

 during the emergence of the moth. Such as are naturally open are broken 

 less than the others; but if only a half dozen threads are sundered, the 

 cocoon is spoiled for reeling pui-poses. All the native cocoons are at times 

 found drilled with large holes, and gutted by birds or squirrels; and those 

 which fall to the ground are frequently destroyed by mice, rats and mole^. 



All the moths are night flyers. All the large heavy worms, when full 

 grown and in a state of nature, hang on the under side of leaves and twigs, 

 being too heavy to sustain themselves in an upright position. They are all of 

 some shade of green — no matter what their color when younger — and in a 



