GASTRIC C/ECA OF THE HETEROPTERA. IIQ 



organism from the caeca of Murgantia, but what appeared to be 

 a pure culture of a very short, actively motile, fluorescent bacillus, 

 which grew vigorously on ordinary media. Although this organ- 

 ism was obtained in culture from ten or more of the dead insects 

 and appeared to be the only one that developed, it was so different 

 from anything that had been expected from the caeca that it was 

 regarded as one of the common fluorescent water bacteria that 

 had probably been present in the anterior part of the alimentary 

 canal and which, after the death of the insect, had invaded the 

 caeca. The culture work on Murgantia was discontinued here, 

 as it apparently promised nothing to warrant any further work. 



In the meantime repeated attempts were also made to cultivate 

 the csecal bacteria from a number of other pentatomids, including 

 chiefly Peribahis limbolarius, Coenus delius, Brochymena quadri- 

 pustulata, Euschistus variolarius and Mormidea lugens, but the 

 results, as with Murgantia, were uniformly negative, neither the 

 caecal organism nor any contamination appearing in the cultures 

 from any of these species, except in exceptional cases where the 

 technique was clearly at fault. 



Common forms such as the squash bug and the chinch bug 

 had been purposely avoided in this work owing to the obvious 

 impossibility of distinguishing between ordinary contaminating 

 organisms and the caecal bacteria typical for these insects; but 

 since the negative results from the work with Murgantia and 

 the other pentatomids showed clearly that the caeca, in these 

 insects at least, were wholly free from foreign bacteria, the 

 possibility of using such insects as Anasa in culture work did 

 not seem so hopeless as at first, especially if it was found that this 

 statement applied also to them. 



As a last resort it was decided to attempt the cultivation of the 

 caecal bacteria from Anasa tristis, this species being selected 

 because it is fairly large and is usually abundant and readily 

 obtainable in winter as well as in summer. 



In the preliminary work on this species, pieces of the caeca 

 were removed and dropped at once into tubes of squash juice 

 bouillon, the composition of which was the same as that of 

 ordinary beef juice bouillon with the addition of a decoction from 

 150 grams of squash stems and leaves per liter. 



