81 FOURTH ANNUAL REPORT OF 



the worms ciiu be reared here with perfect success, and that where the rule^- 

 hiid down under the head of " Best Methods of Eearing " are properly carried 

 out, we ma^' be as sure of a good harvest as they ai'c in most of the silk- 

 ijrowing districts of Europe. 



The worms naturall}" commence to hatch with us from the middle to 

 the end of April. Thej^ commence spinning nsually within thirty days, and 

 remain in the chrysalis state just about two Aveeks. The feature in our cli- 

 mate which we have most to guard against is the excessive heat that some- 

 times occurs in May, when the worms are in their last stage. A wet sjiring 

 with a hot early summer, is most injurious, and these features of 1870 in- 

 duced a greater mortality than occurred during any of the other four years 

 <if my experience. Excessive heat, and too great richness of the food, is 

 very apt to produce jaundice in the worms, and it manifests itself more 

 particularly just before spinning time. Our fall season cannot be surpassed 

 for this industrj^, as the weather is drier, n^ore uniform in temperature, and 

 the leaves are riper and sweeter than in the spring. For these reasons, 

 . future experience will doubtless prove that September and October will be 

 propitious months for rearing the worms ', and that consequently it 

 will be best to retard the hatching of eggs by keejiing them constantly at a 

 temperature below 40° F.; or we might employ the Bivoltins — raising only 

 enough of the first brood to give us a good supply of eggs for the second. 



NATURAL HISTORY OF THE SILKWORM. 



The Silkworm is interesting to us, not only from the value of its silk, 

 but from the fact that it is about the only insect that has been under man's 

 complete management for a long series of years, and that has been carried 

 by him from one country to another in widely- different j^arts of the world. 

 It is, so to speak, the onl}- domesticated insect to which we have been able 

 to ajjpl}' the principle of selection for any length of time; for though the 

 Cochineal insect and the Honey-bee have been in a measure under our con- 

 trol, these principles have never been applied to the former, and it is onl}- 

 within the last few years that we have been enabled, by hive-improvements 

 and deeper knowledge of its habits, to apply them with any degree of satis- 

 faction to the latter. The Silkworm has been subjected to a variety of dif- 

 fering conditions, both of climate and management; and if species are, as 

 many of the more advanced -thinkers now contend, not immutable but muta- 

 ble; we should expect to find great differences in the characteristics of this 

 particular one. These, differences Ave do, in fiict, find ; for it is notorious 

 that there are about as many breeds of the Silkworm, as there are of the 

 domestic Dog. In the form of the egg, the colors of the larva, and more 

 especially in the size, color, form and quality of the cocoon ; and in the 

 varying length of time required for development ; the races of Bombyx mori 

 show such differences that, if found in anv of our wild species, they would 

 be considered as specific b}^ most naturalists. Yet nO naturalist pretends to 

 give these differing races specific scientific names, though they are often 

 designated by po^iular distinguishing terms. 



