1916] Coccidce. and Aphididce on Pines 417 



This sheath consists of viscous saliva and passes through the 

 whole of the open space that has been formed by the solvent 

 action of the saliva to a cell that has just been attacked and 

 where fresh saliva has just been poured out to dissolve the cell 

 wall and contents. As soon as a cell has been pierced, its 

 turgor, or pressure from the inside, which is several atmospheres, 

 gives away. The cell's liquid contents is partly forced by the 

 pressure of the surrounding cells and partly leaks out into the 

 open space. It is then sucked up into the insect's body. 



Plateau* has shown that the saHva of Hemiptera has the 

 power to change starch to sugar. We have proven that this 

 coccid is no exception by the tests made on cells that had just 

 been pierced by the insect. We get negative results with 

 iodin as a test for starch, but Fehling's solution, a test for sugar, 

 gives positive results. The presence of proteid-dissolving 

 and cellulose-dissolving enzymes in the saliva is indicated by 

 the destruction of the cells of the plant by its work. Most of 

 the nutriment is obtained from the mesophyll tissue. This 

 is shown by the number of cells broken up and destroyed or 

 partially destroyed in all of the many sections examined. So 

 we place Chionaspis pinifolicB Fitch in the second class of sucking 

 insects described by Busgen,t "those piercing into the 

 parenchyma by boring through the cells." 



^ It is not possible to say positively whether there is an actual 

 poisoning to the plant by one or more of the enzymes that are 

 injected into its cells. The following evidence points toward 

 such conclusion : The mesophyll tissue is first discolored, then 

 browned and killed, as shown in photomicrograph IV. The 

 killed and discolored mesophyll cells are those shown darkest 

 in the photograph. The mesophyll region near the upper 

 side of the illustration would appear exactly the same as the 

 corresponding area near the lower margin, if the scale had not 

 been sucking in the vicinity of the darkened cells, thereby 

 killing them. This dead tissue extends for a distance much 

 greater than the beak can pierce. 



It is not likely that these cells are merely dried out and 

 starved by withdrawal of liquid coming up from the roots, 



*Plateau, Recherches sur les phenomenes de la digestion les insectes. 1874 

 Bruxelles. 



tBusgen, M., Der Honigtau, Jenaische Zeitschrift fur Naturwissenschaft, 

 Bd. 25, p. 381, 1891. 



