1913] McCulloch: Crithidia leptocoridis 13 



degeneration by staining very lightly in comparison with that of the 

 " kinetonucleus. " The "kinetonucleus" retains its normal size and 

 lies near to the nucleus. It is in such a parasite as that seen in plate 4. 

 figure 7-t, that the clear, threadlike fibers which connect the "kine- 

 tonucleus" with the basal granule can be most readily demonstrated. 

 The rhizoplast is very distinct owing to the tendency of these large 

 forms to become very vacuolate (pi. 4, figs. 85, 86 and 89). The axo- 

 style also can be seen readilj^ in such forms as shown on plate 4, figures 

 74 and 81. 



Under certain conditions the attached forms in the rectum have 

 been observed to become free from the rectal wall and to begin encyst- 

 ment at once. The flagellum coils about the body and coalesces with 

 it (pi. 4, figs. 85, 87, 89 and 91). A reduction in size of the encysting 

 form follows (pi. 4, figs. 102-104). Only one nuclear mass becomes 

 visible (pi. 4, figs. 106-107) and a thick protective covering forms 

 about the spore (pi. 4, fig. 108). The spores thus formed pa.ss out 

 with the excreta in great numbers. 



VI. EELATION OF PARASITE TO HOST 



The box-elder bugs are without doubt casually infected by means 

 of spores or moist excreta taken up with the food. The exact condi- 

 tions under which these insects become infected are not definitely 

 known as yet. The box-elder bugs are vegetable feeders, sucking the 

 juice of the box-elder and maple trees and the fruit of the raspberry. 

 On a few occasions, under laboratory conditions of extreme hunger, 

 several of the more vigorous insects were observed to suck the contents 

 from the digestive tract of another insect in a weakened condition. 

 This was not observed to happen in the presence of an abundance 

 of food. 



Investigations were carried on to determine whether hereditary 

 infection occurs in the box-elder bug, Leptocoridis tririttatus. The 

 ovaries were examined in both the living and sectioned material, and 

 negative results were obtained in every instance. Many nymphs were 

 examined. A majority of the wild nymphs showed infection in the 

 stomach. The percentage of infection increased with the age of the 

 host until mature insects showed 100 per cent infection. Such an 

 infection is also widespread; in these investigations infected insects 

 were obtained from Kansas, California, Washington, Utah and New 

 Mexico. Numerous eggs were obtained and hatched in the laboratory. 



