2 Illinois State Lahopatory of Natural History. 



Hemiptera made at my office this summer by my as- 

 sistant, Mr. John Marten, and myself, it became evident 

 that these dissimilar org-ans could be connected by in- 

 termediate gradations, that they had substantially the 

 same anatomical relations and histological structure, 

 and that all were alike, wherever they oc(.'urred, in the 

 highly remarkable fact that they were invariably loaded 

 with myriads of bacteria, differing in genus and species 

 in the different insects, but always confined to these 

 organs.* We further observed that in CoreidfB and 

 Lygteidse these coecal structures might be present in 

 one genus and absent in another of the same faniilj^ 

 only the higher Hemiptera (Pentatomidre, Scutelleridse, 

 Corimelsenidte, etc.) invariably possessing them, and 

 the lower Hemiptera invariably wanting them. In case 

 they were absent, their bacterial relationship was never 

 assumed, in whole or in part, by any other organ. The 

 occurrence of "masses of motile vibrio-like objects" in 

 these glands in a Pentatoma was noticed by Leydig in 

 1857, but I have found no other mention of the matter 

 than that on page 337 of his Lehrhuch cler Ilistologie. 



There are certain coesal appendages of the alimentary 

 canal of other orders of insects, which have a general 

 resemblance to these in Hemiptera, but can be consid- 

 ered homologous with them only in a very loose sense 

 of the word, since they are certainly not homogenous. 

 These gastric pouches in grasshoppers, cockroaches, and 

 carabid beetles do not commonly contain bacteria so 

 far as we have been able to determine. In fact, the only 

 other insect structures in which we have found bacteria 

 normally present with any constancy, were the fatty 

 bodies of various species of cockroaches. It is not ab- 

 solutely' certain that these objects from cockroaches are 

 bacteria, as they have not yet been cultivated, our 

 own recent efforts having failed, as did Blochmann's.t 



* No hibernating specimens have as yet been examined, and it is possible 

 that this phenomenon will be found to disappear with the functional auies- 

 ccnc;e of these glands. 



+ Biologisches Centralblatt. Vol. VII.. p. 60G. 



