14 



BULLETIN 431, U. S. DEPARTMENT OF AGRICULTURE . 



same plan will be followed and similar terms will be used in describing 

 these stages as were employed in the description of a healthy larva 

 of the same age, the interpretation of the description will be aided 

 if the appearance of a healthy larva as described above is borne in 

 mind. 



First Stage. 



Uncapping a larva showing the first symptoms of the disease, it 

 will be observed that it has assumed a slightly yellowish appearance. 



Fig. 12.— First stage: Larva showing first 

 symptoms of sacbrood and presenting the 

 dorsal view of the anterior third. Cap 

 removed artificially. (Original.) 



This shade deepens somewhat during 

 the stage, but does not become a deep 

 yellow. 



Anterior tliird. — The lateral margins 

 and extreme cephalic end of the an- 

 terior third (fig. 12; PI. II, b, li) may 

 have assumed, and frequently do as- 

 sume, a more or less transparent ap- 

 pearance (represented in the figure by 

 shading). The position and the sur- 

 face markings of the anterior third are 

 approximately those of the normal larva. When a change in the 

 position is observed, however, the extreme anterior end of the larva — 

 the apex of this cone-like third — having settled somewhat, does not 

 approach so near the roof of the cell as does that of a healthy larva. 

 It is sometimes found also that this cone-like third is deflected more 

 or less to one side or the other. 



Middle and posterior thirds. — The changes from the normal that 

 have taken place in these two thirds are similar and can, therefore, be 

 described together. The yellowish tint is here observed. The trans- 

 verse ridges and furrows are still well marked (fig. 13). The trans- 



Fig. 13.— First stage: Ventral view of larva 

 dead of sacbrood as seen from above and at 

 an angle, giving a ventral view of all three 

 thirds. Cap torn across. (Original.) 



