20 



BULLETIK 431, V. S. DEPAETMENT OF AGEIGULTUB13. 



third. The effect of the drying on this third is quite perceptible also. 

 The surface markings and notched majgin of the normal larva are 

 stiU indicated in the decaying remains, but are much less pronoimced. 

 The subcuticular fluid is no longer in evidence. 



ConsisUncy of the cordents of the sac— Upon tearing the sac, the 

 contents are found to be less fluid than in preceding stages. The 

 decaying tissue mass is still granular in appearance. As the drying 



Fia. 22.— Fifth stage: Scale, or larval re- 

 mains, in saobrood as seen on looking 

 into tlie cell. (Original.) 



proceeds further the contents of the 

 sac become pastelike in consistency. 

 Condition of the virus in the fourth 

 stage. — As in the preceding stage, the 

 larval remains in the fourth stage do 

 not seem to be infectious. 



Fifth Stage. 



Fig. 23.— Fifth stage: Scale, or larval remains, 

 in sacbrood viewed at an angle from above. 

 (Original.) 



The dead larva in this last stage 

 has lost by evaporation all of its 

 moistiire, leaving the dry, mummylike remains known as the "scale." 



Anterior third. — The anterior third (fig. 22 ; PL 11, T) through dry- 

 ing is retracted from the mouth of the cell, with the apex drawn stiU 

 deeper into the cell and raised toward its roof. This third is greatly 

 wrinkled, and, being of a very dark-brown color, presents often an 

 almost black appearance. 



Middle third.^ThB middle third (fig. 23; PI. II, r), is deeply 

 concave from side to side and may show remnants of the segmental 

 markings of the larva. The surface is often roughened through 

 drying. Sometimes both longitudinal and transverse tracheae are 



