PSYCHE 



VOL. XXV JUNE, 1918 No. 3 



ON THE EXISTENCE OF IMMUNITY PRINCIPLES IN 



INSECTS.i 



By R. W. Glaser. 



During the course of my work on various diseases of insects, I 

 have often been confronted by results which seemed to point 

 towards the existence of immunity principles. I failed to become 

 convinced, however, till I instituted a series of experiments meant 

 to prove or disprove my views. Other workers, also, on investigat- 

 ing caterpillar and grasshopper diseases, have been unable to ex- 

 plain some of their results without assuming the possibility of 

 physiological immunity, but direct proof for their contentions has 

 been lacking. 



In physiological work of this sort it is very difficult to obtain 

 quantitative data for the reason that the amount of blood obtain- 

 able from a particular insect amounts to only one-tenth to one-fifth 

 of a cubic centimeter. In one series of experiments I managed to 

 obtain quantitative results. The other data are qualitative but, 

 I hope, no less important. 



The Question of Phagocytosis. 



Since all entomological text-books emphasize the importance of 

 the blood cells in ridding the insect body from the invasion of 

 foreign substances this question was first investigated. In prac- 

 tically all the literature on the subject, insect blood cells are com- 

 pared with the mammalian white blood corpuscles. An exceed- 

 ingly aggressive nature is attributed to them and their movements 

 are described as actively amseboid, engulfing foreign substances 

 with great avidity. I was greatly astonished to find that this view 

 was incorrect and that the blood cells are visibly rather passive. 

 Of course, we know that the so-called amsebocytes play an impor- 

 tant r61e during metamorphosis, and I do not wish to create the 



' Contribution from the U. S. Bureau of Entomology in cooperation with the Bussey Insti- 

 tution of Harvard University. (BusSey Institution, No. 143.) 



