268 N. E. McINDOO 



having the top of the thorax black and shiny, due to the loss of 

 hair. Many times their wings are ragged at the tips and poste- 

 rior edges. 



To obtain material for the study of the disposition of the or- 

 gans described by Hicks ('57-'60), workers and drones just 

 emerged from the cells were used. Since queens of this age were 

 not available when needed, older ones were employed. The legs 

 and wings were pulled off at their articulations, and the thoraces 

 and abdomens were slit open. These parts were put into a cold 

 saturated solution of caustic potash, where they remained from 

 one to three days, depending on the size and coloration of the 

 material. When removed from this solution, the material was 

 washed thoroughly in water and mounted between two cover 

 glasses in a one-fifth saturated solution of potassium acetate. This 

 solution gives a good refractive index and at the same time unites 

 readily with the solution of asphaltum used for holding the two 

 cover glasses together. It was thus possible to study the two 

 sides of the specimens under the highest magnification. 



To obtain material for the study of the internal anatomy of 

 the organs herein discussed, worker pupae 13 to 21 days old 

 (counting from the time the eggs were laid) were killed. The 

 various appendages were removed and were then cut into small 

 pieces, which were immediately dropped into fixing fluids. Var- 

 ious fixatives were used but the modified form of Carnoy's proved 

 best. This fluid contains equal parts of absolute alcohol, chloro- 

 form, and glacial acetic acid, with the corrosive sublimate to excess. 

 The material was left in this solution 53^ hours. It was dehy- 

 drated in the ordinary way but was cleared with cedar oil by Using 

 the sinking method. In order not to harden the chitin too much 

 the material was left not more than two minutes each in 95 per 

 cent and in absolute alcohol and not more than 10 minutes in 

 cedar oil. It was then placed for 10 minutes each in ether and in 

 thin celloidin, after which it was put into a vial containing thicker 

 celloidin. The vial was put into melted paraffin and was watched 

 closely, for the celloidin solution boils at a low temperature. It 

 was boiled slowly for 10 minutes, until the celloidin became thick. 

 The material was then removed from the vial, and a small mass 



