GASTRIC CECA OF THE HETEROPTERA. 1 03 



T. J. Burrill in 1883. The specimens firot examined by Professor 

 Forbes were from experimental cages of potted corn in which the 

 insects had been dying in large numbers from some cause which 

 even at the present time is not clearly understood, and upon 

 finding large numbers of specific bacteria in crushed preparations 

 of these insects he at first very naturally regarded them as the 

 probable cause of the trouble, and proceeded to investigate the 

 matter with characteristic thoroughness, with a view to the pos- 

 sible utilization of this organism as a means of controlling the 

 chinch bug in the field. After a careful study, however, he was 

 finally forced to the conclusion that the bacteria were not para- 

 sitic upon the chinch bug at all, but that they were really normal 

 to the caecal appendages of healthy bugs and that they probably 

 had some important function in the metabolism of the insect. 

 He also established later, by the examination of a great variety 

 of insects of different orders, and especially'of Heteroptera, 

 that the chinch bug was not unique in this regard, but that 

 the same phenomenon also occurred in a number of other species 

 of Lygaeidae as well as in representatives of several other families 

 of Heteroptera, and that wherever the caeca were present in this 

 group, they were always filled with specific bacteria. A large 

 part of this work was never published and the unpublished notes, 

 which proved to be of the greatest assistance in this work, were 

 turned over to me by Professor Forbes for use in continuing a 

 study of the subject. 



The problem as it was suggested to me by Professor Forbes 

 was primarily to determine the significance of the presence of 

 these "normal" bacteria of the caeca to work out, if possible, 

 the relation existing between the insects and their characteristic 

 intestinal flora, and also, indirectly, to determine whether the 

 occurrence of these complex caecal structures might not throw 

 some light on the phylogeny of the Heteroptera. 



The following study was carried on under the supervision of 

 Professor Forbes, and I consider it an honor to be in a position 

 to express my indebtedness to him for his constant aid and 

 encouragement throughout the course of the work. 



I am also greatly indebted to Dr. W. J. MacNeal, in whose 

 laboratory I was very kindly permitted to do a considerable 



