100 THE GYPSY MOTH APPENDIX. 



The results of these analyses show that phosphate of pot- 

 ash, although varying in amount, is a constant ingredient of 

 the digestive fluids of leaf-eating Lepidoptera, and this fact 

 gives additional evidence of the importance of the substance. 

 We would call particular attention to the fact that but little 

 of this compound was found in the excrement examined 

 (Nos. 2, 9). This shows that the phosphate of potash is 

 retained in the system, since the analyses of the alimentary 

 canals of the corresponding insects (Nos. 1, 8) revealed a 

 fair amount of the substance. 



THE FUNCTION or PHOSPHATE OF POTASH IN LEPIDOPTERA. 



In the larvae examined, phosphate of potash was always 

 found associated with albuminoids. This coincidence, which 

 is also common in plants, seems to show that in living or- 

 ganisms there is an intimate relationship between these sub- 

 stances. Schumacher states that if alkaline phosphates " are 

 mixed with a solution of albumen, or if a solution of them 

 is permitted to diffuse against one of albumen, a much 

 greater amount of the latter will pass through the membrane 

 than would otherwise be the case." 



In the fluid obtained as a result of the dialysis of the 

 digestive systems of dispar larvee a small amount of albumen 

 was found associated with the phosphate of potash. This 

 albumen would not coagulate upon the application of heat, 

 but was precipitated by the addition of alcohol. 



From the physiological stand-point the natural inference 

 is that the phosphate of potash aids in the assimilation of 

 albuminoids. The facts in the case may be briefly stated as 

 follows : 



Albuminous substances form an important part of the in- 

 sect's food. The process of assimilation in dispar is one 

 of osmosis. Albuminous substances do not readily pass 

 through the stomach walls, but phosphate of potash aids 

 them in their diffusion. Since this compound is present in 

 such large quantities, it seems evident that its function is, as 

 stated, to aid in the osmosis of albuminoids through the 

 walls of the alimentary canal into the blood. 



" Physik der Pflanze, " 1867, p. 129. 



