:86 FOURTH ANNUAL REPORT OF 



In short, the ordinary Silkworm bears unmistakable evidence of having 

 been modified according to man's wants. He has been interested mainly in 

 producing the largest amount of silk from the smallest amount of leaves, 

 and -we consequently find to-day vast differences in the cocoons of the dif- 

 ferent races, and great bulk of cocoon compared with the insect which 

 makes it. 



The Mulberry- silkworm is anomalous in one other respect, namely, in 

 having a curved horn on the eleventh joint; for though in those silkworms 

 which are tubercled, there is always a large middle tubercle on the back of 

 this eleventh joint, yet none of them possess this Sphingidous character in 

 the same degree.* 



From the foregoing, it will become obvious that what follows of the 

 natural histor}^ of the Silkworm is of the most general character. 



The Ego. — The egg is nearly round, a little flattened, and in size rather 

 less than a mustard seed. It is yellow when first deposited, and so renuiins 

 if unimpregnated,! but when impregnated soon acquires a gray or slate 

 color and becomes indented. It is fiistened by a gummy substance which 

 the moth secretes in the act of ovipositing. Each female will lay upwards 

 of 300 eggs. One ounce of good eggs will produce 40,000 worms. The 

 color of the albuminous fluid in the egg corresponds, or is correlated with, 

 that of the cocoon ; so that when this fluid is white the worms produce 

 white cocoons, and when yellow the}' Avill produce yellow ones. 



As the hatching point approaches^, the egg becomes more pale in color 

 which is due to the intervening space between the rolled-up worm and the 

 shell which is semi-transparent. Just before the worm hatches there is 

 often heard a slight clicking noise, which, however, is commoH to many 

 other insect eggs ; and when loosened it will sometimes bound a short dis- 

 tance, evidently b}^ the sudden jerk of the worm within, as in the case of 

 some so-called jumping seeds and jumping galls. 



The Larva.— The newly hatched worm, as already stated, is black or 

 dark gray. It is covered with long stiff hairs, and if closely examined these 

 hairs will be found to spring from pale tubercles of the same number and 

 placed precisely in the same position as those to be found at the same age 



on all the other silk- 



worms to be hereafter 

 described. It becomes 

 paler at each moult 

 and after feeding for 

 nearly a month, pre- 



Tlns teatuve is ffeiieran\ couMdeied &o entuely chai.icti iistic ot the larvre of a Familv of Moths 



worm whicli appi-artMl on thi- cdvi-v of the Amfrican. Entomoloqist . To me this horu exhibits merely 

 11 case'of persistence of the miaaie tubercle on the eleventh joint, while those on the other joints have 

 become obsolete ; and we liave an approach to the same condition in our Promethea (t ig. 43, d) , which, 

 as it ffi-ows, loses all its tnl)ercles except four near the head and this one on the eleventh joint. 



t On very rare occasimis the embryo in unimpregnated eggs continues to develop and the young 

 worm has even been known to hatcli. 



