278 Illinois State Laboratory of Natural History. 



mately became very tender and easily ruptured, while the blood, 

 unusually copious, was thin and yellow instead of its normal 

 limpid or grayish color. Other larvae became slug.gish, con- 

 tinued to eat, but consumed only a small quantity of food, the 

 body gradually became flaccid, the skin wrinkled and tough, 

 and the color a grayish or leaden tint, and finally nearly black. 

 These, hours or even one or two days before their death, 

 adhered by their prolegs, or some of them, to a support, and 

 remained quiet, at length only showing signs of vitality when 

 touched, and at last dying while still firmly anchored to the 

 limb or other object upon which they rested. After, and for 

 some time before, death, the flaccid body hung directly downward 

 from the point of attachment. If this latter happened to be 

 near the middle of the body, the two ends hung down, the parts 

 nearly parallel with each other. From these dead and black- 

 ened worms a decided and characteristic odor of putrescence 

 was perceptible, tainting, when numerous, the air of the well- 

 ventilated room." 



The first of these diseases was also characterized in the 

 Statistical Record of the State Board of Agriculture for Au- 

 gust, 1885, by Mr. Woodworth. who conducted the experi- 

 ment for Prof. Burrill. " This disease," he says, '' does not 

 make its appearance until the worms are about ready to 

 spin, that is, near the end of the last age. The body of the 

 affected worms assumes a somewhat granular, yellow color, 

 instead of the natural, bright semi-transparent hue. This 

 change of color also differs from the normal change, in that 

 the yellow is first on the middle of the segment instead of at 

 the ends. The skin becomes soft and tender, breaking at the 

 least fall, and allowing the yellow body fluid to escape more 

 readily than wounds of equal size would in healthy worms. 

 The affected worms become very restless, crawling about and 

 shrinking in size from loss of blood until they finally die. A 

 few spins cocoons, which are generally soft, often bright 

 orange, and sometimes so thin that the pupa or dead worm may 

 be seen within. Some of the worms even pupate without spin- 

 ning, and from these pupae moths may emerge, which will 

 sometimes deposit their eggs. When a brood of worms is 

 attacked by this disease generally very few survive." 



